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  • Articles  (1,409,091)
  • Articles: DFG German National Licenses  (1,409,091)
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  • 101
    Electronic Resource
    Electronic Resource
    A search for the fourth SM family quarks at the Tevatron (2005)
    Springer
    The European physical journal 39 (2005), S. 499-501 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. It is shown that the fourth standard model (SM) family quarks can be observed at the Fermilab Tevatron if their anomalous interactions with known quarks have sufficient strength.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2004-02110-2
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  • 102
    Electronic Resource
    Electronic Resource
    Non-perturbative pion matrix element of a twist-2 operator from the lattice (2005)
    Springer
    The European physical journal 40 (2005), S. 69-80 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We give a continuum limit value of the lowest moment of a twist-2 operator in pion states from non-perturbative lattice calculations. We find that the non-perturbatively obtained renormalization group invariant matrix element is $\langle x\rangle_{\mathrm{RGI}} = 0.179(11)$ , which corresponds to $\langle x \rangle^{\overline{\mathrm{MS}}}(2\mathrm{ GeV}) = 0.246(15)$ . In obtaining the renormalization group invariant matrix element, we have controlled important systematic errors that appear in typical lattice simulations, such as non-perturbative renormalization, finite size effects and effects of a non-vanishing lattice spacing. The crucial limitation of our calculation is the use of the quenched approximation. Another question that remains not fully clarified is the chiral extrapolation of the numerical data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2005-02121-5
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  • 103
    Electronic Resource
    Electronic Resource
    Complete description of polarization effects in e + e - pair productionby a photon in the field of a strong laser wave (2005)
    Springer
    The European physical journal 40 (2005), S. 27-40 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We consider production of a e + e - pair by a high-energy photon in the field of a strong laser wave. A probability of this process for circularly or linearly polarized laser photons and for arbitrary polarization of all other particles is calculated. We obtain the complete set of functions which describe such a probability in a compact invariant form. Besides, we discuss in some detail the polarization effects in the kinematics relevant to the problem of $e\to \gamma$ conversion at $\gamma \gamma$ and ${\gamma e}$ colliders.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2005-02125-1
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  • 104
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    The role of strange sea quarks in chiral extrapolations on the lattice (2005)
    Springer
    The European physical journal 40 (2005), S. 81-96 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Since the strange quark has a light mass of order $O(\Lambda_{\mathrm {{QCD}}})$ , fluctuations of sea $s\bar{s}$ pairs may play a special role in the low-energy dynamics of QCD by inducing significantly different patterns of chiral symmetry breaking in the chiral limits N f = 2 (m u = m d = 0, m s physical) and N f = 3 (m u = m d = m s = 0). This effect of vacuum fluctuations of $s\bar{s}$ pairs is related to the violation of the Zweig rule in the scalar sector, described through the two O(p 4) low-energy constants L 4 and L 6 of the three-flavour strong chiral lagrangian. In the case of significant vacuum fluctuations, three-flavour chiral expansions might exhibit numerical competition between leading- and next-to-leading-order terms according to the chiral counting, and chiral extrapolations should be handled with special care. We investigate the impact of the fluctuations of $s\bar{s}$ pairs on chiral extrapolations in the case of lattice simulations with three dynamical flavours in the isospin limit. Information on the size of the vacuum fluctuations can be obtained from the dependence of the masses and decay constants of pions and kaons on the light quark masses. Even in the case of large fluctuations, corrections due to the finite size of spatial dimensions can be kept under control for large enough boxes ( $L\sim 2.5$ fm).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2005-02130-4
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  • 105
    Electronic Resource
    Electronic Resource
    Radiative K e3 decays revisited (2005)
    Springer
    The European physical journal 40 (2005), S. 205-227 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Motivated by recent experimental results and ongoing measurements, we review the chiral perturbation theory prediction for $K_{\mathrm {L}}\to\pi^{\mp} e^{\pm} \nu_e\gamma$ decays. Special emphasis is given to the stability of the inner bremsstrahlung-dominated relative branching ratio versus the K e3 form factors, and on the separation of the structure-dependent amplitude in differential distributions over the phase space. For the structure-dependent terms, an assessment of the order p 6 corrections is given, in particular, a full next-to-leading order calculation of the axial component is performed. The experimental analysis of the photon energy spectrum is discussed, and other potentially useful distributions are introduced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2005-02123-3
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  • 106
    Electronic Resource
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    Extension of the Buchalla-Safir bound (2005)
    Springer
    The European physical journal 40 (2005), S. 187-191 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. I provide a simple derivation of the Buchalla-Safir bound on $\gamma$ . I generalize it to the case where an upper bound on the phase of the penguin pollution is assumed. I apply the Buchalla-Safir bound, and its generalization, to the most recent data on CP violation in $B \to \pi^ + \pi^-$ .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2005-02142-0
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  • 107
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    The Lorentz and CPT violating effects on the $Z\rightarrow l^ + l^-$ decay (2005)
    Springer
    The European physical journal 40 (2005), S. 269-273 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We study the Lorentz and CPT violating effects on the branching ratio, the CPT violating asymmetry and the ratio of the decay width, including only the Lorentz violating effects, to the one obtained in the standard model, for the flavor dependent part of the lepton flavor conserving $Z\rightarrow l^ + l^-$ ( $l = e,\mu,\tau $ ) decay. The inclusion of the Lorentz and CPT violating effects in the standard model contribution are too small to be detected, since the corresponding coefficients are highly suppressed at the low energy scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2005-02146-8
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  • 108
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    Measurement of $F_2^{c\bar{c}}$ and $F_2^{b\bar{b}}$ at high Q 2 using the H1 vertex detector at HERA (2005)
    Springer
    The European physical journal 40 (2005), S. 349-359 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Measurements are presented of inclusive charm and beauty cross sections in e + p collisions at HERA for values of photon virtuality Q 2 〉 150 GeV2 and of inelasticity 0.1 〈 y 〈 0.7. The charm and beauty fractions are determined using a method based on the impact parameter, in the transverse plane, of tracks to the primary vertex, as measured by the H1 vertex detector. The data are divided into four regions in Q 2 and Bjorken x, and values for the structure functions $F_2^{c\bar{c}}$ and $F_2^{b\bar{b}}$ are obtained. The results are found to be compatible with the predictions of perturbative quantum chromodynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2005-02154-8
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  • 109
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    Measurement of event shape distributions and moments in e + e $^-\rightarrow \mathrm{hadrons}$ at 91-209 GeV and a determination of $\ensuremath{\alpha_{\mathrm{s}}}$ (2005)
    Springer
    The European physical journal 40 (2005), S. 287-316 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We have studied hadronic events from e + e- annihilation data at centre-of-mass energies from 91 to 209 GeV. We present distributions of event shape observables and their moments at each energy and compare with QCD Monte Carlo models. From the event shape distributions we extract the strong coupling $\ensuremath{\alpha_{\mathrm{s}}}$ and test its evolution with energy scale. The results are consistent with the running of $\ensuremath{\alpha_{\mathrm{s}}}$ expected from QCD. Combining all data, the value of $\ensuremath{\alpha_{\mathrm{s}}} \ensuremath{(M_{\mathrm{Z}})}$ is determined to be $$ \ensuremath{\alpha_{\mathrm{s}}}\ensuremath{M_{\mathrm{Z}}} = 0.1191 \pm0.0005 \mathrm{(stat.)} \pm0.0010\mathrm{(expt.)} \pm0.0011 \mathrm{(hadr.)} \pm0.0044 \mathrm{(theo.)}\,. $$ The energy evolution of the moments is also used to determine a value of $\ensuremath{\alpha_{\mathrm{s}}}$ with slightly larger errors: $\ensuremath{\alpha_{\mathrm{s}}} \ensuremath{M_{\mathrm{Z}}}=0.1223\pm 0.0005(\mathrm{stat.})\pm 0.0014(\mathrm{expt.})\pm 0.0016(\mathrm{hadr.})^{+0.0054}_{-0.0036}(\mathrm{theo.})$ .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2005-02120-6
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  • 110
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    Sneutrino production at e + e - linear colliders: addendum to slepton production (2005)
    Springer
    The European physical journal 40 (2005), S. 435-445 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Complementing the preceding study of charged scalar leptons, the sector of the neutral scalar leptons, sneutrinos, is investigated in a high-precision analysis for future e + e - linear colliders. The theoretical predictions for the cross-sections are calculated at the thresholds for non-zero widths and in the continuum including higher-order corrections at the one-loop level. Methods for measuring the sneutrino masses and the electron-sneutrino-gaugino Yukawa couplings are presented, addressing theoretical problems specific for the sneutrino channels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2005-02148-6
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  • 111
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    Heavy quark vacuum polarization: first two moments of the ${\mathcal{O}}(\alpha_s^3 n_f^2)$ contribution (2005)
    Springer
    The European physical journal 40 (2005), S. 361-366 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The vacuum polarization due to a virtual heavy quark pair and specifically the coefficients of its Taylor expansion in the external momentum are closely related to moments of the cross section for quark-antiquark pair production in electron-positron annihilation. Relating measurement and theoretically calculated Taylor coefficients, an accurate value for charm- and bottom-quark mass can be derived, once corrections from perturbative QCD are sufficiently well under control. Up to three-loop order these have been evaluated previously. We now present a subset of four-loop contributions to the lowest two moments, namely those from diagrams which involve two internal loops from massive and massless fermions coupled to virtual gluons, hence of order $\alpha_s^3 n_f^2$ . The calculation demonstrates the applicability of Laporta’s algorithm to four-loop vacuum diagrams with both massive and massless propagators and should be considered a first step towards the full evaluation of the order $\alpha_s^3$ contribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2005-02151-y
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  • 112
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    Optimal observables and phase-space ambiguities (2005)
    Springer
    The European physical journal 40 (2005), S. 497-503 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Optimal observables are known to lead to minimal statistical errors on parameters for a given normalised event distribution of a physics reaction. Thereby all statistical correlations are taken into account. Therefore, on the one hand they are a useful tool to extract values on a set of parameters from measured data. On the other hand one can calculate the minimal constraints on these parameters achievable by any data-analysis method for the specific reaction. In case the final states can be reconstructed without ambiguities optimal observables have a particularly simple form. We give explicit formulae for the optimal observables for generic reactions in case of ambiguities in the reconstruction of the final state and for general parameterisation of the final-state phase space.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2005-02153-9
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  • 113
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    Yukawa coupling structure in intersecting D-brane models (2005)
    Springer
    The European physical journal 40 (2005), S. 579-587 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The structure of Yukawa coupling matrices is investigated in type IIA T 6/(Z2 x Z2) orientifold models with intersecting D-branes. Yukawa coupling matrices are difficult to be made realistic in conventional models in which the generation structure emerges by the multiple intersection of D-branes in the factorized T 6 = T 2 x T 2 x T 2. We study the new type of flavor structure, where Yukawa couplings are dynamically generated, and show this type of models lead to non-trivial structures of Yukawa coupling matrices, which can be realistic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2005-02166-4
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  • 114
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    QCD analysis of dijet production at low Q 2 at HERA (2005)
    Springer
    The European physical journal 40 (2005), S. 469-472 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Recent H1 data on triple differential dijet cross sections in $e^\pm p$ interactions in the region of low photon virtualities are shown to be in reasonable agreement with the predictions of the NLO QCD calculations obtained using the program NLOJET + + . The implications of this observation for the phenomenological relevance of the concept of resolved virtual photon are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2005-02172-6
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  • 115
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    Exclusive semileptonic rare decays $B \to K^{(*)} l^ + l^-$ in a SUSY SO(10) GUT (2005)
    Springer
    The European physical journal 40 (2005), S. 565-577 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. In the SUSY SO(10) GUT context, we study the exclusive processes $B \to K^{(*)} l^ + l^-(l = \mu,\tau)$ . Using the Wilson coefficients of the relevant operators including the new operators $\smash{Q_{1,2}^{(\prime)}}$ which are induced by neutral Higgs boson (NHB) penguins, we evaluate some possible observables associated with these processes like the invariant mass spectrum (IMS), lepton pair forward-backward asymmetry (FBA), lepton polarization asymmetries etc. In this model the contributions from Wilson coefficients $C_{Q_{1,2}}^\prime$ , among new contributions, are dominant. Our results show that the NHB effects are sensitive to the FBA, $\mathrm {d}L/\mathrm {d}\hat{s}$ , and $\mathrm {d}T/\mathrm {d}\hat{s}$ of $B \to K^{(*)} \tau^ + \tau^-$ decay, which are expected to be measured in B factories, the deviation of $\mathrm {d}T/\mathrm {d}\hat{s}$ in $B \to K \mu^ + \mu^-$ can reach 0.1 from SM, which could be seen in B factories, and the average of the normal polarization $\mathrm {d}N/\mathrm {d}\hat{s}$ can reach several percent for $B \to K \mu^ + \mu^-$ and it is 0.05 or so for $B\to K \tau^ + \tau^-$ , which could be measured in the future super B factories and provide useful information to probe new physics and discriminate different models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2005-02132-2
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  • 116
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    Corrections to quark asymmetries at LEP (2005)
    Springer
    The European physical journal 40 (2005), S. 493-496 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The most precise measurement of the weak mixing angle $\sin^2 \theta_{\mathrm{eff}}^l$ at LEP is from the forward-backward asymmetry $e^ + e^- \rightarrow b \overline{b}$ at the Z-pole. In this note the QED and electroweak radiative corrections to obtain the pole asymmetry from the measured asymmetry for b- and c-quarks have been calculated using ZFITTER, which has been amended to allow a consistent treatment of partial two-loop corrections for the b-quark final asymmetries. A total correction of $\delta A_{\mathrm{FB}}^{{b}} = 0.0019 \pm 0.0002$ and $\delta A_{\mathrm{FB}}^{{c}} = 0.0064 \pm 0.0001$ has been found, where the remaining theoretical uncertainty is much too small to explain the apparent discrepancy between $\sin^2 \theta_{\mathrm{eff}}^l$ obtained from A FB b and from the left-right asymmetry at SLD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2005-02164-6
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  • 117
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    Probing the perturbative NLO parton evolution in the small-x region (2005)
    Springer
    The European physical journal 40 (2005), S. 515-517 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. A dedicated test of the perturbative QCD NLO parton evolution in the very small-x region is performed. We find a good agreement with recent precision HERA data for F 2 p(x,Q 2), as well as with the present determination of the curvature of F 2 p. Characteristically, perturbative QCD evolutions result in a positive curvature which increases as x decreases. Future precision measurements in the very small x-region, x 〈 10-4, could provide a sensitive test of the range of validity of perturbative QCD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2005-02167-3
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  • 118
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    The QCD pomeron in ultraperipheral heavy ion collisions: IV. Photonuclear production of vector mesons (2005)
    Springer
    The European physical journal 40 (2005), S. 519-529 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The photonuclear production of vector mesons in ultraperipheral heavy-ion collisions is investigated within the QCD color dipole picture, with particular emphasis on the saturation model. The integrated cross section and the rapidity distribution for the $AA \rightarrow V AA$ ( $V = \rho, \omega, \phi, J/\Psi$ ) process are computed and theoretical estimates for scattering on both light and heavy nuclei are given for the energies of RHIC and LHC. A comparison with the recent STAR data on coherent production of $\rho$ mesons is also presented. Furthermore, we calculate the photoproduction of vector mesons in proton-proton collisions at RHIC, Tevatron and LHC energies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2005-02175-3
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  • 119
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    Realistic neutrino masses from multi-brane extensions of the Randall-Sundrum model? (2005)
    Springer
    The European physical journal 40 (2005), S. 539-554 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Scenarios based on the existence of large or warped (Randall-Sundrum model) extra dimensions have been proposed for addressing the long standing puzzle of the gauge hierarchy problem. Within the contexts of both those scenarios, a novel and original type of mechanism generating small (Dirac) neutrino masses, which relies on the presence of additional right-handed neutrinos that propagate in the bulk, has arisen. The main objective of the present study is to determine whether this geometrical mechanism can produce reasonable neutrino masses also in the interesting multi-brane extensions of the Randall-Sundrum model. We demonstrate that, in some multi-brane extensions, neutrino masses in agreement with all relevant experimental bounds can indeed be generated but at the price of a constraint (stronger than the existing ones) on the bulk geometry, and that the other multi-brane models even conflict with those experimental bounds.
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    URL: http://dx.doi.org/10.1140/epjc/s2005-02165-5
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  • 120
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    Confinement from new global defect structures (2005)
    Springer
    The European physical journal 40 (2005), S. 531-537 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We investigate confinement from new global defect structures in three spatial dimensions. The global defects arise in models described by a single real scalar field, governed by special scalar potentials. They appear as electrically, magnetically or dyonically charged structures. We show that they induce confinement, when they are solutions of effective QCD-like field theories in which the vacua are regarded as color dielectric media with an antiscreening property. As expected, in three spatial dimensions the monopole-like global defects generate the Coulomb potential as part of several confining potentials.
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    URL: http://dx.doi.org/10.1140/epjc/s2005-02168-2
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  • 121
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    On the properties of cycles of simple Boolean networks (2005)
    Springer
    The European physical journal 43 (2005), S. 115-124 
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    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We study two types of simple Boolean networks, namely two loops with a cross-link and one loop with an additional internal link. Such networks occur as relevant components of critical K=2 Kauffman networks. We determine mostly analytically the numbers and lengths of cycles of these networks and find many of the features that have been observed in Kauffman networks. In particular, the mean number and length of cycles can diverge faster than any power law.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2005-00034-6
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  • 122
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    Mean field theory and geodesics in general relativity (2005)
    Springer
    The European physical journal 43 (2005), S. 143-154 
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    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. It is proven that all geodesics in a mean gravitational field can be interpreted locally as the averages of geodesics in the unaveraged field. The respective time-like, space-like or null character of averaged and unaveraged geodesics is discussed carefully. Finally, some important astrophysical and cosmological applications and consequences are investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2005-00037-3
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  • 123
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    The H+ related defects involved in domain reversal for both near-stoichiometric and heavily Mg-doped lithium niobate crystals (2005)
    Springer
    The European physical journal 43 (2005), S. 347-353 
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    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Domain reversal was performed on both near-stoichiometric and heavily Mg-doped lithium niobate crystals. H+ related defect structures in these two types of crystals were studied through the infrared absorption spectra. It is found that the intensity of some decomposed peaks of absorption band change apparently during domain reversal for near-stoichiometric lithium niobate crystals but not for heavily Mg-doped lithium niobate crystals. According to these experimental results, distinct models about H+ related defect structure in LiNbO3 lattice were supposed for them. Nb4+Li and Mg3-Nb were considered as the centers of H+ related defect complex for near-stoichiometric and heavily Mg-doped lithium niobate crystals respectively. Different behavior of them was used to explain the difference of infrared absorption spectra during domain reversal between two types of crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2005-00062-2
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  • 124
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    Integrable spin-boson interaction in the Tavis-Cummings model from a generic boundary twist (2005)
    Springer
    The European physical journal 43 (2005), S. 387-391 
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    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We construct models describing interaction between a spin s and a single bosonic mode using a quantum inverse scattering procedure. The boundary conditions are generically twisted by generic matrices with both diagonal and off-diagonal entries. The exact solution is obtained by mapping the transfer matrix of the spin-boson system to an auxiliary problem of a spin-j coupled to the spin-s with general twist of the boundary condition. The corresponding auxiliary transfer matrix is diagonalized by a variation of the method of Q-matrices of Baxter. The exact solution of our problem is obtained applying certain large-j limit to su(2)j, transforming it into the bosonic algebra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2005-00068-8
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  • 125
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    Acoustic radiation force due to incident plane-progressive waves on coated spheres immersed in ideal fluids (2005)
    Springer
    The European physical journal 43 (2005), S. 379-386 
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    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. In this study, the acoustic radiation force resulting from the interaction of a plane progressive wave with a coated sphere was examined. The linear acoustic scattering problem was obtained first by solving the classical boundary conditions to obtain the required coefficients. The radiation force was then determined by averaging the momentum flux tensor expressed in terms of the total scattering pressure or velocity potential in an ideal fluid. Numerical calculations of the radiation force function Yp , which is the radiation force per unit energy density and unit cross-section, were displayed versus the dimensionless size parameter x=k1 b (k1 is the wave number in the exterior fluid and b the radius of the uncoated sphere) over a large range of frequencies. Particular emphasis has been focused on the coating thickness and the absorption of sound inside the outer covering layer. The fluid-loading effect on the radiation force function curves was also analysed.
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    Rayleigh-Schrödinger-Goldstone variational perturbation theory for many Fermion systems (2005)
    Springer
    The European physical journal 43 (2005), S. 393-398 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We present a Rayleigh-Schrödinger-Goldstone perturbation formalism for many Fermion systems. Based on this formalism, variational perturbation scheme which goes beyond the Gaussian approximation is developed. In order to go beyond the Gaussian approximation, we identify a parent Hamiltonian which has an effective Gaussian vacuum as a variational solution and carry out further perturbation with respect to the renormalized interaction using Goldstone’s expansion. Perturbation rules for the ground state wavefunctional and energy are found, thus, opening a way for general use of the Schrödinger picture method for many Fermion systems. Useful commuting relations between operators and the Gaussian wavefunctional are also found, which could reduce the calculational efforts substantially. As examples, we calculate the first order correction to the Gaussian wavefunctional and the second order correction to the ground state of an electron gas system with the Yukawa-type interaction.
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    Optoelectronic properties of zinc blende ZnSSe and ZnBeTe alloys (2005)
    Springer
    The European physical journal 43 (2005), S. 3-9 
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    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The compositional dependence of the electronic band structure has been computed for zinc blende ZnSxSe1-x and Zn1-xBexTe alloys with composition x ranging from 0 to 1. The empirical pseudo potential method with the virtual crystal approximation have been used. A particlar attention has been paid to the effect of alloy disorder on the electronic properties of the II-VI studied compounds. For this purpose, the compositional disorder is added to the virtual crystal approximation as an effective potential. Such correction approximates significantly our calculated values of the band gap bowing parameters to experimental ones. The ZnSxSe1-x gap energy shows a nonlinear behavior with strong bowing for low compositions of sulfur. The Zn1-xBexTe compound, as it is known, can be direct or indirect semiconductor depending on its beryllium composition x. The electron effective mass and the refractive index have been investigated as well. Polynomial approximations are obtained for both the energy gap and the effective mass as functions of alloy composition at Γ and X valleys.
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    Melting and evaporation transitions in small Al clusters: canonical Monte-Carlo simulations (2005)
    Springer
    The European physical journal 43 (2005), S. 47-52 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. A dimer of bound atoms cannot melt, only dissociate. Bulk metals show a well defined first order transition between their solid and liquid phases. The appearance of the melting transition is explored for increasing clusters sizes via the signatures in the specific heat and the root mean square of the bond lengths δB (Berry parameter) by means of Monte-Carlo simulations of Al clusters modelled by Gupta potentials. Clear signatures of a melting transition appear for N∼6 atoms. Closed-shell effects are shown for clusters with up to 56 atoms. The melting transition is compared in detail with the dissociation transition, which induces a second and possibly much larger local maximum in the specific heat at higher temperatures. Larger clusters are shown to fragment into dimers and trimers, which in turn dissociate at higher temperatures.
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    Lattice vibrational analysis of polyacene (2005)
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    The European physical journal 43 (2005), S. 53-64 
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    Notes: Abstract. Within an extended Su-Schrieffer-Heeger model, we made a lattice vibrational analysis of polyacene. In a singly-charged polyacene, the ground state contains an interchain-coupled polaron of quasi-D2h symmetry, around which we found thirteen localized modes in total. Among these localized modes, five (three B2u and two B3u) are infrared active, six (four Ag and two B1g) modes are Raman active, and the other two localized modes are asymmetric, which are both infrared active and Raman active. For the case a charged polaron is coupled with a neutral soliton in a finite polyacene chain, the vibrational modes are also calculated to display the coupling effect between self-trapping excitations on phonons. It is found that the localized phonons are determined mainly by the charged polaron, but the number and frequencies of the localized modes are influenced by the existence of the neutral soliton.
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    Phase diagram in the quantum XY model with long-range interactions (2005)
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    The European physical journal 43 (2005), S. 93-96 
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    Notes: Abstract. We study the d-dimensional quantum XY model with ferromagnetic long-range interaction decaying as r-p in terms of boson operators, by employing the coherent state path integral approach. We have obtained a finite critical temperature as a function of the dimension (d) for d〈p〈2d. For p〉2d the system becomes disordered at all temperatures. For the particular values p=3/2 and d=1 our theoretical calculations are comparable to those from Monte Carlo simulations.
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    Disturbing synchronization: Propagation of perturbations in networks of coupled oscillators (2005)
    Springer
    The European physical journal 43 (2005), S. 97-108 
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    Topics: Physics
    Notes: Abstract. We study the response of an ensemble of synchronized phase oscillators to an external harmonic perturbation applied to one of the oscillators. Our main goal is to relate the propagation of the perturbation signal to the structure of the interaction network underlying the ensemble. The overall response of the system is resonant, exhibiting a maximum when the perturbation frequency coincides with the natural frequency of the phase oscillators. The individual response, on the other hand, can strongly depend on the distance to the place where the perturbation is applied. For small distances on a random network, the system behaves as a linear dissipative medium: the perturbation propagates at constant speed, while its amplitude decreases exponentially with the distance. For larger distances, the response saturates to an almost constant level. These different regimes can be analytically explained in terms of the length distribution of the paths that propagate the perturbation signal. We study the extension of these results to other interaction patterns, and show that essentially the same phenomena are observed in networks of chaotic oscillators.
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    Fractal geometry of critical Potts clusters (2005)
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    The European physical journal 43 (2005), S. 155-155 
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    A density functional study of molecular oxygen adsorption and reaction barrier on Pu (100) surface (2005)
    Springer
    The European physical journal 43 (2005), S. 131-141 
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    ISSN: 1434-6036
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    Topics: Physics
    Notes: Abstract. Oxygen molecule adsorptions on a Pu(100) surface have been studied in detail, using the generalized gradient approximation to density functional theory. Dissociative adsorption with a layer by layer alternate spin arrangement of the plutonium layer is found to be energetically more favorable compared to molecular adsorption. Hor2 approach on a bridge site without spin polarization was found to the highest chemisorbed site with an energy of 8.787 eV among all the cases studied. The second highest chemisorption energy of 8.236 eV, is the spin-polarized Hor2 or Ver approach at center site. Inclusion of spin polarization affects the chemisorption processes significantly, non-spin-polarized chemisorption energies being typically higher than the spin-polarized energies. We also find that the 5f electrons to be more localized in spin-polarized cases compared to the non-spin-polarized counterparts. The ionic part of O-Pu bonding plays a significant role, while the Pu 5f-O 2p hybridization was found to be rather week. Also, adsorptions of oxygen push the top of 5f band deeper away from the Fermi level, indicating further bonding by the 5f orbitals might be less probable. Except for the interstitial sites, the work functions increase due to adsorptions of oxygen.
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    On voltage-current characteristics and critical current in Bi-2212 (2005)
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    The European physical journal 43 (2005), S. 39-45 
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    Notes: Abstract. V(I) characteristics have been performed in a monocrystalline microbridge of Bi[ Pb $]-2212$ . The vortex phase diagram has been greatly investigated. Linear but non-ohmic Voltage (Current) (V(I)) curves with a well defined critical current have been observed. A departure from this behavior is observed near the peak effect where an out of equilibrium high threshold current can be stabilized. At high temperature, the critical current persists in the “liquid” state despite the dissipation at the lowest bias. Some implications of these results are discussed. In particular, it is proposed that the surface disorder, rather than the bulk disorder, is responsible for the vortex pinning in this sample.
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    Hydrogen desorption from ball milled MgH2 catalyzed with Fe (2005)
    Springer
    The European physical journal 43 (2005), S. 19-27 
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    Topics: Physics
    Notes: Abstract. In order to obtain faster hydrogen sorption kinetics, MgH2-Fe nanocomposites were prepared by high-energy ball milling. The MgH2 decomposition was studied in samples obtained by changing in a systematic way both the catalyst amount and the degree of microstructural refinement. To this purpose, blends containing increasing Fe concentration have been ball milled in processing conditions able to impart different amount of structural defects. The resulting samples have been characterized by X-ray diffraction to investigate the microstructural features and the phase composition, while the powder morphology and the degree of catalyst dispersion were analyzed by scanning electron microscopy. Differential scanning calorimetry was carried out to characterize the hydrogen desorption behavior of these nanocomposites. Experimental results clearly show that the characteristics of the desorption process are dominated, among other factors, by the morphology of the catalyst dispersion, which in turns depends on the processing conditions and blend composition. In order to achieve low desorption temperatures the homogeneous catalyst dispersion in micron-size particles throughout the structure is required. This condition can be achieved by suitable tuning of the milling conditions and of the catalyst amount.
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    Generic two-phase coexistence in nonequilibrium systems (2005)
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    The European physical journal 43 (2005), S. 73-79 
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    Topics: Physics
    Notes: Abstract. A beautifully simple model introduced a couple of decades ago, Toom’s cellular automaton, revealed that non-equilibrium systems may exhibit generic bistability, i.e. two-phase coexistence over a finite area of the (two-dimensional) phase diagram, in violation of the equilibrium Gibbs phase rule. In this paper we analyse two interfacial models, describing more realistic situations, that share with Toom’s model a phase diagram with a broad region of phase coexistence. An analysis of the interfacial models yields conditions for generic bistability in terms of physically relevant parameters that may be controlled experimentally.
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    A model reaction diffusion system under spatial perturbation: theoretical and numerical investigation (2005)
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    The European physical journal 43 (2005), S. 109-114 
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    Topics: Physics
    Notes: Abstract. We consider a model (Lengyel-Epstein) reaction-diffusion system under spatial parametric modulation and demonstrate the effect of resonance shift of the Hopf-Turing boundary. A systematic perturbative and numerical analysis shows that this shift may induce spatial inhomogeneity on an homogeneous stable state resulting in pattern formation.
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    Decoherence and entanglement in coherent quantum tunneling of magnetization with dissipation (2005)
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    The European physical journal 43 (2005), S. 125-129 
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    Notes: Abstract. We study the coherent quantum tunneling of magnetization, for example, in a biaxial molecular magnet with dissipation of the environment which results in the suppression of the tunneling and therefore the decoherence of superposition of macroscopic quantum states in terms of the general spin-boson model. The degree of entanglement between the magnet and the environment is evaluated explicitly with the help of reduced density matrix. We show an interesting relation that the degree of entanglement approaches maximum value when the coherent tunneling is suppressed completely.
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    Magnetic structure of the spin-1/2 layer compound NaNiO2 (2005)
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    The European physical journal 43 (2005), S. 159-162 
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    Topics: Physics
    Notes: Abstract. We have carried out high resolution neutron powder diffraction experiments aiming at a determination of the magnetic structure of the S=1/2 layer compound NaNiO2. The magnetic moments are ferromagnetically aligned in the NiO2 layers and antiparallel between layers. The direction of the magnetic moment has a small component along the a-direction.
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    Fermionic Ising glasses in magnetic transverse field with BCS pairing interaction (2005)
    Springer
    The European physical journal 43 (2005), S. 187-193 
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    Topics: Physics
    Notes: Abstract. We study a fermionic infinited-ranged Ising spin glass with a real space BCS interaction in the presence of an applied transverse field. The problem is formulated in the integral functional formalism where the SU(2) spins are given in terms of bilinear combinations of Grassmann fields. The problem is solved within static approximation and the replica symmetry ansatz combined with previous approaches used to study the critical behavior of the quantum Ising spin glass in a transverse field and the spin glass Heisenberg model with BCS pairing. Our results show that the transverse field has strong effect in the phase boundary of the spin glass phase and the PAIR phase in which there is a long range order corresponding to formations of pairs. The location of the tricritical point in the PAIR phase transition line is also affected.
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    Crossover component in non critical dissipative sandpile models (2005)
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    The European physical journal 43 (2005), S. 213-220 
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    ISSN: 1434-6036
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    Topics: Physics
    Notes: Abstract. The effect of bulk dissipation on non critical sandpile models is studied using both multifractal and finite size scaling analyses. We show numerically that the local limited (LL) model exhibits a crossover from multifractal to self-similar behavior as the control parameters hext and epsilon turn towards their critical values, i.e. hext →0+ and epsilon→epsilonc. The critical exponents are not universal and exhibit a continuous variation with epsilon. On the other hand, the finite size effects for the local unlimited (LU), non local limited (NLL), and non local unlimited (NLU) models are well described by the multifractal analysis for all values of dissipation rate epsilon. The space-time avalanche structure is studied in order to give a deeper understanding of the finite size effects and the origin of the crossover behavior. This result is confirmed by the calculation of the susceptibility.
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    Nonextensive thermostatistic properties of a q-generalized Fermi system (2005)
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    The European physical journal 43 (2005), S. 271-277 
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    Topics: Physics
    Notes: Abstract. Based on the generalized statistic distribution derived from the Tsallis’ entropy that has been successfully used in complex systems with long-range interactions and/or long-duration memory, the thermostatistic properties of a q-generalized Fermi system are studied. The total number of particles, internal energy, and heat capacity at constant volume are calculated for two different cases of q≤1 and q≥1, respectively, where q is an important parameter to evaluate the nonextensivity of the system. The thermostatistic characteristics of the system are discussed in detail. It is found from the results obtained here that the Fermi energy of such a system is independent of the parameter q and is equal to that of an original ideal Fermi system when q≤1, while other thermostatistic properties of the system depend closely on the parameter q. For example, when q〈1, the chemical potential of the system in certain region of temperature may be larger than the Fermi energy; when q〉1, some thermodynamic parameters of the system at low temperatures must be cut off.
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    The effect of iron doping in La0.8Sr0.2Fe0.05Co0.95O3-δ perovskite (2005)
    Springer
    The European physical journal 43 (2005), S. 297-303 
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    Topics: Physics
    Notes: Abstract. La0.8Sr0.257Fe0.05Co0.95O3-δ perovskite is investigated by 57Fe transmission and emission Mössbauer spectroscopy, X-ray diffraction, AC magnetic susceptibility and magnetotransport measurements. Temperature dependence of the 57Fe Mössbauer isomer shift, quadrupole splitting, magnetic hyperfine field, line broadening, and relative spectral area is presented in a detailed manner for La0.8Sr0.257Fe0.05Co0.95O3-δ . The oxidation state of iron is determined to be Fe3+, and the presence of preferential electronic charge compensation Fe3+ ↦  Fe4+ over that of Co3+ ↦ Co4+ is excluded. Relaxation of iron magnetic moments reflected by the 57Fe Mössbauer spectra of La0.8Sr0.257Fe0.05Co0.95O3-δ are interpreted as evidence for the existence of superparamagnetic like Co clusters and a corresponding cluster glass magnetic phase formed below T ≈65 K.
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    Electrical and magnetic properties of Gd(Ba2-xLax)Cu3O7+δ (2005)
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    The European physical journal 43 (2005), S. 305-318 
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    Notes: Abstract. We have studied the structural, electrical, and magnetic properties of the normal and superconducting states Gd(Ba2-xLax)Cu3O7+δ [Gd(BaLa)123] samples with 0.0 ≤x ≤0.8 prepared by the standard solid-state reaction. XRD characterization shows an orthorhombic-tetragonal structural transition at x=0.2. Iodometric titration analysis shows the oxygen content of the samples increase with the increase of La doping. The resistivity curves show that for x≤0.15, there is metallic behavior, and for x≥0.2, there is a gradual insulating transition behavior in the normal state. The metal-insulator and superconductor-insulator transitions occur between x=0.35 and x=0.4. The superconducting transition temperature decreases with the increase of La content as two-step curve. The normal-state resistivity is fitted for two and three dimensional variable range hopping (2D&3D-VRH) and Coulomb gap (CG) regimes, separately. The results show that the dominant mechanism is CG for x≤0.35, and VRH for x≥0.4. The pinning energy U, derived from the thermally activated flux creep (TAFC) model and Ambegaokar-Halperin (AH) theory, shows a power-law relation as U∼H -β. The critical current density decreases with the increase of La doping and magnetic field. The E-J curves show that the induced electric field increases with the increase of magnetic field and La concentration. The magnetization measurements indicate that the critical penetration fields and magnetic current density decrease with La doping.
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    A molecular dynamics investigation of dynamical heterogeneity in supercooled water (2005)
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    The European physical journal 43 (2005), S. 355-362 
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    Topics: Physics
    Notes: Abstract. We investigate the presence of dynamical heterogeneity in supercooled water with molecular dynamics simulations using the new water model proposed by Mahoney and Jorgensen [M.W. Mahoney, W.L. Jorgensen J. Chem. Phys. 112, 8910 (2000)]. Prompted by recent theoretical results [J.P. Garrahan, D. Chandler, Phys. Rev. Lett. 89, 35704 (2002)] we study the dynamical aggregation of the least and the most mobile molecules. We find dynamical heterogeneity in supercooled water and string-like dynamics for the most mobile molecules. We also find the dynamical aggregation of the least mobile molecules. The two kinds of dynamical aggregation appear however to be very different. Characteristic times are different and evolve differently. String-like motions appear only for the most mobile molecules, a result predicted by the facilitation theory. The aggregation of the least mobile molecules is more organized than the bulk while the opposite is observed for the most mobile molecules.
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    Self organized scale-free networks from merging and regeneration (2005)
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    The European physical journal 43 (2005), S. 369-372 
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    Notes: Abstract. We propose that the ubiquitous scale free nature of many real world networks may emerge from a steady state process where nodes are created and merged randomly. The merging may be viewed as an optimization of efficiency by minimizing redundancy.
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    Spin-polarized transport through a coupled double-dot (2005)
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    The European physical journal 43 (2005), S. 421-427 
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    Notes: Abstract. We investigate the quantum transport through a mesoscopic device consisting of an open, lateral double-quantum-dot coupled by time oscillating and spin-polarization dependent tunneling which results from a static magnetic field applied in the tunneling junction. In the presence of a non-vanishing bias voltage applied to two attached macroscopic leads both spin and charge currents are driven through the device. We demonstrate that the spin and charge currents are controllable by adjusting the gate voltage, the frequency of driving field and the magnitude of the magnetic field as well. An interesting resonance phenomenon is observed.
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    Modeling the pion and kaon form factors in the timelike region (2005)
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    The European physical journal 39 (2005), S. 41-54 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. New, accurate measurements of the pion and kaon electromagnetic form factors are expected in the near future from experiments at electron-positron colliders, using the radiative return method. We construct a model for the timelike pion electromagnetic form factor that is valid also at momentum transfers far above the $\rho$ resonance. The ansatz is based on vector dominance and includes a pattern of radial excitations expected from dual resonance models. The form factor is fitted to the existing data in the timelike region, continued to the spacelike region and compared with the measurements there and with the QCD predictions. Furthermore, the model is extended to the kaon electromagnetic form factor. Using isospin and SU(3)-flavor symmetry relations we extract the isospin-one contribution and predict the kaon weak form factor accessible in semileptonic $\tau$ decays.
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    Longitudinal $\bar{\Lambda}_0$ polarization in heavy-ion collisions as a probe for QGP formation (2005)
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    The European physical journal 39 (2005), S. 95-99 
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    Notes: Abstract. We present an analysis of the longitudinal $\bar{\Lambda}_0$ polarization in ultrarelativistic heavy-ion collisions. The polarization of $\bar{\Lambda}_0$ ’s coming from the decay chain $\bar{\Xi}\rightarrow \bar{\Lambda}_0 + \pi$ exhibits a very well differentiated behavior depending on the production region of the primordial $\bar{\Xi}$ ’s. This effect reflects the different values of the $N_{\bar{\Xi}}/N_{\bar{\Lambda}_0}$ ratio in the QGP region, where nucleon-nucleon interactions take place in a hot and dense environment, and the peripherical region, in which ordinary nucleon-nucleon interactions occur. An increase in the longitudinal $\bar{\Lambda}_0$ polarization signals a strangeness enhancement which is thought of as a property of the QGP phase.
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    The low-lying mass spectrum of the N = 1 SU(2) SUSY Yang-Mills theory with Wilson fermions (2005)
    Springer
    The European physical journal 39 (2005), S. 87-94 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We analyze the low energy spectrum of bound states of the N = 1 SU(2) SUSY Yang-Mills Theory (SYM). This work continues the investigation of the non-perturbative properties of SYM by Monte Carlo simulations in the Wilson discretization with dynamical gluinos. The dynamics of the gluinos is included by the Two-Step Multi-Bosonic Algorithm (TSMB) for dynamical fermions. A new set of configurations has been generated on a $16^3\cdot 32$ lattice at $\beta = 2.3$ and $\kappa = 0.194$ . The analysis also includes sets of configurations previously generated on a smaller ( $12^3\cdot 24$ ) lattice at $\kappa = 0.1925, 0.194$ and 0.1955. Guided by predictions from low energy Lagrangians, we consider spin-1/2, scalar and pseudoscalar particles. The spectrum of SYM is a challenging subject of investigation because of the extremely noisy correlators. In particular, meson-like correlators contain disconnected contributions. The larger time-extension of the $16^3\cdot 32$ lattice allows to observe two-state signals in the effective mass. Finite-volume effects are monitored by comparing results from the two lattice sizes.
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    Renormalization of the neutrino mass operators in the multi-Higgs-doublet standard model (2005)
    Springer
    The European physical journal 39 (2005), S. 219-227 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We derive the renormalization group equations (RGE) for the flavor coupling matrices of the effective dimension-five operators which yield Majorana neutrino masses in the multi-Higgs-doublet standard model; in particular, we consider the case where two different scalar doublets occur in those operators. We also write down the RGE for the scalar-potential quartic couplings and for the Yukawa couplings of that model, in the absence of quarks. As an application of the RGE, we consider two models which, based on a μ- $\tau$ interchange symmetry, predict maximal atmospheric neutrino mixing, together with U e3 = 0, at the seesaw scale. We estimate the change of those predictions due to the evolution of the coupling matrices of the effective mass operators from the seesaw scale down to the electroweak scale. We derive an upper bound on that change, thereby finding that the radiative corrections to those predictions are in general negligible.
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    URL: http://dx.doi.org/10.1140/epjc/s2004-02075-0
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    T-dependent Dyson-Schwinger equation in IR regime of QCD: the critical point (2005)
    Springer
    The European physical journal 39 (2005), S. 209-218 
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    ISSN: 1434-6052
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    Topics: Physics
    Notes: Abstract. The quark mass function $\Sigma(p)$ in QCD is revisited, using a gluon propagator in the form 1/(k 2 + m g 2) plus $2\mu^2/ (k^2 + m_g^2)^2$ , where the second (IR) term gives linear confinement for m g = 0 in the instantaneous limit, μ being another scale. To find $\Sigma(p)$ we propose a new (differential) form of the Dyson-Schwinger equation (DSE) for $\Sigma(p)$ , based on an infinitesimal subtractive renormalization via a differential operator which lowers the degree of divergence in integration on the RHS, by two units. This warrants $\Sigma(p-k)\approx \Sigma(p)$ in the integrand since its k-dependence is no longer sensitive to the principal term (p-k)2 in the quark propagator. The simplified DSE (which incorporates the Ward-Takahashi (WT) identity in the Landau gauge) is satisfied for large p 2 by $\Sigma(p)$ = $\Sigma(0)/(1 + \beta p^2)$ , except for Log factors. The limit p 2 = 0 determines $\Sigma_0$ . A third limit, p 2 = -m 0 2, defines the dynamical mass m 0 via $\Sigma({\mathrm {i}} m_0) = + m_0$ . After two checks ( $f_{\pi} = 93\pm 1$ MeV and $ \langle q{\bar{q}}\rangle $ = $(280 \pm 5 {\mathrm {MeV}})^3$ ), for $1.5 〈 \beta 〈 2$ with $\Sigma_0 = 300 $ MeV, the T-dependent DSE is used in the real time formalism to determine the “critical” index $\gamma = 1/3$ analytically, with the IR term partly serving as the H-field. We find $T_{\mathrm {c}} = 180 \pm 20 $ MeV and check the vanishing of $f_{\pi}$ and $ \langle q{\bar{q}}\rangle $ at T c.
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    URL: http://dx.doi.org/10.1140/epjc/s2004-02072-3
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    Nuclear parton distribution functions and energy-loss effect in the Drell-Yan reaction off nuclei (2005)
    Springer
    The European physical journal 39 (2005), S. 179-184 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The energy-loss effect in nuclear matter is another nuclear effect apart from the nuclear effects on the parton distribution as in deep inelastic scattering process. The quark energy loss can be measured best by the nuclear dependence of the high energy nuclear Drell-Yan process. By means of two typical kinds of quark energy-loss parametrization and the different sets of nuclear parton distribution functions, we present an analysis of the E866 experiments on the nuclear dependence of Drell-Yan lepton pair production resulting from the bombardment of Be, Fe and W targets by 800 GeV protons at Fermilab. It is found that the quark energy loss in cold nuclei is strongly dependent on the used nuclear parton distribution functions. The further prospects of using relatively low energy protons incident on nuclear targets are presented by combining the quark energy-loss rate determined from a fit to the E866 nuclear-dependent ratios versus x 1, with the nuclear parton distribution functions given from lA deep inelastic scattering (DIS) data. The experimental study of the relatively low energy nuclear Drell-Yan process can give valuable insight in the energy loss of the fast quark propagating through cold nuclei and help to pin down nuclear parton distribution functions.
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    Transverse-momentum-ordered showers and interleaved multiple interactions (2005)
    Springer
    The European physical journal 39 (2005), S. 129-154 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We propose a sophisticated framework for high-energy hadronic collisions, wherein different QCD physics processes are interleaved in a common sequence of falling transverse-momentum values. Thereby phase-space competition is introduced between multiple parton-parton interactions and initial-state radiation. As a first step we develop new transverse-momentum-ordered showers for initial- and final-state radiation, which should be of use also beyond the scope of the current article. These showers are then applied in the context of multiple interactions, and a few tests of the new model are presented. The article concludes with an outlook on further aspects, such as the possibility of a shower branching giving partons participating in two different interactions.
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    Spectrum of recoil nucleons in quasi-elastic neutrino-nucleus interactions (2005)
    Springer
    The European physical journal 39 (2005), S. 195-200 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We have analyzed the consequences of introducing the local density approximation combined with an effective nuclear momentum-dependent potential into the CC quasi-elastic neutrino-nucleus scattering. We note that the distribution of recoil nucleons momenta becomes smooth for low momentum values and the sharp threshold is removed. Our results may be relevant for Sci-Fi detector analysis of K2K experiments. The total amount of observed recoil protons is reduced because some of them remain bound inside the nucleus. We compare theoretical predictions for a probability of such events with the results given by NUX + FLUKA MC simulations.
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    Energy dependence of gap survival probability and antishadowing (2005)
    Springer
    The European physical journal 39 (2005), S. 435-438 
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    Topics: Physics
    Notes: Abstract. We discuss the energy dependence of the gap survival probability which follows from the rational form of the amplitude unitarization. In contrast to the eikonal form of unitarization which leads to a decreasing energy dependence of the gap survival probability, we predict a non-monotonous form for this dependence.
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    High-precision predictions for the MSSM Higgs sector at ${{\mathcal{O}}}(\alpha_b\alpha_s)$ (2005)
    Springer
    The European physical journal 39 (2005), S. 465-481 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We evaluate $\mathcal{O}{\alpha_b \alpha_s}$ corrections in the Higgs boson sector of the $\mathcal{C}P$ -conserving MSSM, generalising the known result in the literature to arbitrary values of $\tan\beta$ . A detailed analysis of the renormalisation in the bottom/scalar bottom sector is performed. Concerning the lightest MSSM Higgs boson mass, we find relatively small corrections for positive μ, while for $\mu 〈 0$ the genuine two-loop $\mathcal{O}{\alpha_b \alpha_s}$ corrections can amount up to 3 GeV. Different renormalisation schemes are applied and numerically compared. It is demonstrated that some care has to be taken in choosing an appropriate renormalisation prescription in order to avoid artificially large corrections. The residual dependence on the renormalisation scale is investigated, and the remaining theoretical uncertainties from unknown higher-order corrections in this sector are discussed for different regions of the MSSM parameter space.
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    Anomalous suppression of $\pi^0$ production at large transverse momentum in Au + Au and d + Au collisions at $\sqrt{{\bf s}_{\bf NN}} = 200$ GeV (2005)
    Springer
    The European physical journal 40 (2005), S. 129-135 
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    Topics: Physics
    Notes: Abstract. We propose a model of the suppression of large p T pions in heavy ion collisions based on the interaction of the large p T pion with the dense medium created in the collision. The model is practically the same as the one previously introduced to describe $J/\psi$ suppression. Both the p T and the centrality dependence of the data are reproduced. In deuteron-gold collisions, the effect of the final state interaction with the dense medium turns out to be negligibly small. Here the main features of the data are also reproduced both at mid and at forward rapidities.
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    Determination of A FB b at the Z pole using inclusive charge reconstruction and lifetime tagging (2005)
    Springer
    The European physical journal 40 (2005), S. 1-25 
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    ISSN: 1434-6052
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    Topics: Physics
    Notes: Abstract. A novel high precision method measures the b-quark forward-backward asymmetry at the Z pole on a sample of 3,560,890 hadronic events collected with the DELPHI detector in 1992 to 2000. An enhanced impact parameter tag provides a high purity b sample. For event hemispheres with a reconstructed secondary vertex the charge of the corresponding quark or anti-quark is determined using a neural network which combines in an optimal way the full available charge information from the vertex charge, the jet charge and from identified leptons and hadrons. The probability of correctly identifying b-quarks and anti-quarks is measured on the data themselves comparing the rates of double hemisphere tagged like-sign and unlike-sign events. The b-quark forward-backward asymmetry is determined from the differential asymmetry, taking small corrections due to hemisphere correlations and background contributions into account. The results for different centre-of-mass energies are: $$ A_{\mathrm{FB}}^{{\mathrm{b}}} (89.449 \mathrm{GeV}) = 0.0637 \pm 0.0143(\mbox{stat.}) \pm 0.0017(\mbox{syst.})$$ $$A_{\mathrm{FB}}^{{\mathrm{b}}} (91.231 \mathrm{GeV}) = 0.0958 \pm 0.0032(\mbox{stat.}) \pm 0.0014(\mbox{syst.})$$ $$A_{\mathrm{FB}}^{{\mathrm{b}}} (92.990 \mathrm{GeV}) = 0.1041 \pm 0.0115(\mbox{stat.}) \pm 0.0024(\mbox{syst.})$$ . Combining these results yields the b-quark pole asymmetry $$ A_{\mathrm{FB}}^{{\mathrm{b, 0}}} = 0.0972 \pm 0.0030(\mbox{stat.}) \pm 0.0014(\mbox{syst.}) . $$
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    Factorisation, parton entanglement and the Drell-Yan process (2005)
    Springer
    The European physical journal 40 (2005), S. 55-61 
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    Topics: Physics
    Notes: Abstract. We discuss the angular distribution of the lepton pair in the Drell-Yan process, $\text{hadron} + \text{hadron}\to\gamma^* + X\to l^ + + l^- + X$ . This process gives information on the spin-density matrix $\rho^{(q,\bar{q})}$ of the annihilating quark-antiquark pair in $q + \bar{q}\to l^ + + l^-$ . There is strong experimental evidence that even for unpolarised initial hadrons $\rho^{(q,\bar{q})}$ is non-trivial, and therefore the quark-antiquark system is polarised. We discuss the possibilities of a general $\rho^{(q,\bar{q})}$ - which could be entangled - and a factorising $\rho^{(q,\bar{q})}$ . We argue that instantons may lead to a non-trivial $\rho^{(q,\bar{q})}$ of the type indicated by experiments.
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    Collins effect in single spin asymmetries of the $p^{\uparrow}p \to \pi X$ process (2005)
    Springer
    The European physical journal 40 (2005), S. 63-67 
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    Topics: Physics
    Notes: Abstract. We investigate the Collins effect in single spin asymmetries (SSAs) of the $p^{\uparrow}p \to \pi X$ process by taking into account the transverse momentum dependence of the microscopic sub-process cross sections, with the transverse momentum in the Collins function integrated over. We find that the asymmetries due to the Collins effect can only explain the available data at best qualitatively, by using our choices of quark distributions in the quark-diquark model and a pQCD-based analysis, together with several options of the Collins function. Our results indicate the necessity to take into account contributions from other effects such as the Sivers effect or twist-3 contributions.
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    Infrared regularization for spin-1 fields (2005)
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    The European physical journal 40 (2005), S. 97-119 
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    Topics: Physics
    Notes: Abstract. We extend the method of infrared regularization to spin-1 fields. As applications, we discuss the chiral extrapolation of the rho meson mass from lattice QCD data and the pion-rho sigma term.
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    The polarization tensor of neutral gluons in external fields at high temperature (2005)
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    The European physical journal 40 (2005), S. 121-127 
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    Topics: Physics
    Notes: Abstract. The one-loop polarization operator of neutral gluons in the background constant Abelian isotopic, H 3, and hypercharge, H 8, chromomagnetic fields combined with A 0 electrostatic potential at high temperature is calculated. The case when A 0 = 0 is investigated separately. The proper time method is applied. It is found that neutral gluons do not acquire magnetic masses in the background fields, in contrast to the charged ones. The application of the results are discussed.
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    Final-state radiation in electron-positron annihilation into a pion pair (2005)
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    The European physical journal 40 (2005), S. 41-54 
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    Topics: Physics
    Notes: Abstract. The process of e + e - annihilation into a $\pi^ + \pi^-$ pair with radiation of a photon is considered. The amplitude of the reaction $e^ + e^- \to \pi^ + \pi^- \gamma$ consists of the model independent initial-state radiation (ISR) and model dependent final-state radiation (FSR). The general structure of the FSR tensor is constructed from Lorentz covariance, gauge invariance and discrete symmetries in terms of the three invariant functions. To calculate these functions we apply chiral perturbation theory (ChPT) with vector and axial-vector mesons. The contribution of the $e^ + e^- \to \pi^ + \pi^- \gamma$ process to the muon anomalous magnetic moment is evaluated, and results are compared with the dominant contribution in the framework of a hybrid model, consisting of VMD and point-like scalar electrodynamics. The developed approach allows us also to calculate the $\pi^ + \pi^-$ charge asymmetry.
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    Possible non-decoupling effects of heavy Higgs bosons in $e^ + e^- \to W^ + W^-$ within THDM (2005)
    Springer
    The European physical journal 40 (2005), S. 137-144 
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    Topics: Physics
    Notes: Abstract. We discuss the origin of the non-decoupling effects of the heavy Higgs bosons within the two Higgs doublet extension (THDM) of the standard model (SM) and illustrate it by means of the one-loop calculation of the differential cross sections of the process $e^ + e^- \to W^ + W^-$ in both the decoupling and the non-decoupling regimes. We argue that there are many regions in the THDM parametric space in which the THDM and SM predictions differ by several percents and such effects could, at least in principle, be testable at the future experimental facilities.
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    Neutrino dimuon production and the strangeness asymmetry of the nucleon (2005)
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    The European physical journal 40 (2005), S. 145-156 
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    Topics: Physics
    Notes: Abstract. We have performed the first global QCD analysis to include the CCFR and NuTeV dimuon data, which provide direct constraints on the strange and antistrange parton distributions, s(x) and $\bar{s}(x)$ . To explore the strangeness sector, we adopt a general parametrization of the non-perturbative $s(x), \bar{s}(x)$ functions satisfying basic QCD requirements. We find that the strangeness asymmetry, as represented by the momentum integral $[S^{-}]\equiv \int_0^1 x [s(x)-\bar{s}(x)] \mathrm dx$ , is sensitive to the dimuon data provided the theoretical QCD constraints are enforced. We use the Lagrange multiplier method to probe the quality of the global fit as a function of [S -] and find -0.001 〈 [S -] 〈 0.004. Representative parton distribution sets spanning this range are given. Comparisons with previous work are made.
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    Universality of the transverse momentum distributions in the framework of percolation of strings (2005)
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    The European physical journal 40 (2005), S. 229-241 
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    Topics: Physics
    Notes: Abstract. In the framework of percolation of color sources, the transverse momentum distribution in heavy ion and p + p collisions at all centralities and energies are shown to follow a universal behavior. The width of the distribution depends on the fluctuations of the number of color sources per cluster. At low densities, there are only independent single color sources, no fluctuations occur and the distribution is described by a single exponential. At very high densities, only one cluster of many color sources appears and therefore there are not fluctuations either and the hardness of the distribution is suppressed. The Cronin effect in this framework is due to a maximum of the fluctuations which decreases as the density increases. We obtain a good agreement with experimental data including the low p T behavior and the spectra for different particles. We show that the transverse momentum and multiplicity distributions are related to each other in a defined way. This point is satisfied by the experimental data on p + p collisions at different energies.
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    New gauge bosons from the littlest Higgs modeland the process $e^{ + }e^{-}\rightarrow t\bar{t}$ (2005)
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    The European physical journal 40 (2005), S. 251-258 
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    Topics: Physics
    Notes: Abstract. In the context of the littlest Higgs (LH) model, we study the process $e^{ + }e^{-}\rightarrow t\bar{t}$ . We find that the new gauge bosons Z H and B H can produce significant correction effects on this process, which can be further enhanced by suitably polarized beams. In most of the parameter space preferred by the electroweak precision data, the absolute value of the relative correction parameter $R_{B_{H}}$ is larger than 5 %. As long as $1 {\mathrm {TeV}} \leq M_{Z_{H}}\leq 1.5 {\mathrm {TeV}} $ and $0.3\leq c\leq 0.5,$ the absolute value of the relative correction parameter $R_{Z_{H}}$ is larger than $5\%$ . With reasonable values of the parameters of the LH model, the possible signals of the new gauge bosons B H and Z H can be detected via the process $e^{ + }e^{-}\rightarrow t\bar{t}$ in the future LC experiments with the CM energy $\sqrt{S} = 800 {\mathrm {GeV}} $ . B H exchange and Z H exchange can generate significantly corrections to the forward-backward asymmetry $A_{\mathrm {{FB}}}(t\bar{t})$ only in a small part of the parameter space.
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    A flavor symmetry for quasi-degenerate neutrinos: $L_\mu - L_\tau$ (2005)
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    The European physical journal 40 (2005), S. 259-268 
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    Topics: Physics
    Notes: Abstract. We consider the flavor symmetry $L_\mu - L_\tau$ for the neutrino mass matrix. The most general neutrino mass matrix conserving $L_\mu - L_\tau$ predicts quasi-degenerate neutrino masses with one maximal and two zero mixing angles. The presence of $L_\mu - L_\tau$ can also be motivated by the near-bimaximal form of the neutrino mixing matrix. Furthermore, it is a special case of $\mu \tau$ symmetric mass matrices. Breaking the flavor symmetry by adding a small flavor-blind term to the neutrino mass matrix and/or by applying radiative corrections is shown to reproduce the observed neutrino oscillation phenomenology. Both the normal and inverted mass ordering can be accommodated within this scheme. Moderate cancellation for neutrinoless double beta decay is expected. The observables |U e3|2 and $\vert 1/2 - \sin^2\theta_{23}\vert$ are proportional to the inverse of the fourth power of the common neutrino mass scale. We comment on whether the atmospheric neutrino mixing is expected to lie above or below $\pi/4$ . We finally present a model based on the see-saw mechanism which generates a light neutrino mass matrix with an (approximate) $L_\mu - L_\tau$ flavor symmetry. This is a minimal model with just one standard Higgs doublet and three heavy right-handed neutrinos. It needs only small values for the soft $L_\mu - L_\tau$ breaking terms to reproduce the phenomenological viable mass textures analyzed.
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    Renormalization-group improved calculation of the $B\to X_s\gamma$ branching ratio (2005)
    Springer
    The European physical journal 40 (2005), S. 165-186 
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    Topics: Physics
    Notes: Abstract. Using results on soft-collinear factorization for inclusive B-meson decay distributions, a systematic study of the partial $B\to X_s\gamma$ decay rate with a cut $E_\gamma\ge E_0$ on photon energy is performed. For values of E 0 below about 1.9 GeV, the rate can be calculated without reference to shape functions using a multi-scale operator product expansion (MSOPE). The transition from the shape-function region to the MSOPE region is studied analytically. The resulting prediction for the $B\to X_s\gamma$ branching ratio depends on three large scales: m b , $\sqrt{m_b\Delta}$ , and $\Delta = m_b-2E_0$ . Logarithms associated with these scales are resummed at next-to-next-to-leading logarithmic order. While power corrections in $\Lambda_{\mathrm {QCD}}/\Delta$ turn out to be small, the sensitivity to the scale $\Delta\approx 1.1$ GeV (for $E_0\approx 1.8$ GeV) introduces significant perturbative uncertainties, which so far have been ignored. The new theoretical prediction for the $B\to X_s\gamma$ branching ratio with $E_\gamma\ge 1.8$ GeV is $\mbox{Br}(B\to X_s\gamma) = \smash{(3.38_{ -0.42}^{ + 0.31}\pm 0.31)}\times 10^{-4}$ , where the first error is an estimate of perturbative uncertainties and the second one reflects uncertainties in input parameters. With this cut $\smash{(89_{ -7}^{ + 6} \pm 1)}\%$ of all events are contained. When this fraction is combined with the previously best prediction for the total decay rate, one obtains $\mbox{Br}(B\to X_s\gamma) = (3.30_{ -0.35}^{ + 0.31}\pm 0.17)\times 10^{-4}$ , with a somewhat less conservative estimate of parametric uncertainties. The implications of larger theory uncertainties for new physics searches are briefly explored with the example of the type-II two-Higgs-doublet model, for which the lower bound on the charged-Higgs mass is reduced compared with previous estimates to approximately 200 GeV at 95% confidence level.
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    Flavour-independent h0A0 search and two Higgs doublet model interpretation of neutral Higgs boson searches at LEP (2005)
    Springer
    The European physical journal 40 (2005), S. 317-332 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Upper limits on the cross-section of the pair-production process ${\ensuremath{{\mathrm{e}}^ + {\mathrm{e}}^-}} \to \mathrm{h}^0 \mathrm{A}^0$ , assuming 100 $\%$ branching fraction to hadrons, are derived from a new search for the $\mathrm{h}^0\mathrm{A}^0 \to $ hadrons final state, independently of the hadronic flavour of the decay products. This study, combined with previously published searches for the neutral Higgs bosons h0 and A0, is used to constrain the Type II Two Higgs Doublet Model (2HDM(II)) with no CP violation in the Higgs sector and no additional non-Standard Model particles besides the five Higgs bosons. The analysis combines LEP1 and LEP2 data collected with the OPAL detector up to the highest available centre-of-mass energies. The searches are sensitive to the $\mathrm{h}^0, \mathrm{A}^0 \to \mathrm{q\bar{q}}, {\ensuremath{\mathrm{g}\mathrm{g}}}, {\ensuremath{\tau^ + \tau^-}}$ and $\mathrm{h}^0\to\mathrm{A}^0\mathrm{A}^0$ decay modes of the Higgs bosons. A benchmark scan of the 2HDM(II) parameter space is performed. Large regions of the 2HDM(II) parameter space explored are excluded at the 95% CL in the ( $m_{\mathrm{h}}, m_{\mathrm{A}}), (m_{\mathrm{h}}, \tan{\beta})$ and $(m_{\mathrm{A}}, \tan{\beta})$ planes, using both direct neutral Higgs boson searches and indirect limits derived from Standard Model high precision measurements. The region $1 \lesssim m_{\mathrm{h}} \lesssim 55$ GeV and $3 \lesssim m_{\mathrm{A}} \lesssim 63$ GeV is excluded at 95 % CL, independently of $m_{\mathrm{h}}, m_{\mathrm{A}}, \tan{\beta}$ and for selected values of $\alpha$ which are representative of a complete $\alpha$ -scan.
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    URL: http://dx.doi.org/10.1140/epjc/s2005-02122-4
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    Pomeron vertices in perturbative QCD in diffractive scattering (2005)
    Springer
    The European physical journal 40 (2005), S. 419-433 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We analyze the momentum space triple pomeron vertex in perturbative QCD. In addition to the standard form of this vertex which is used in the context of total cross sections at high energies and in the QCD reggeon field theory, there exists an alternative form which has to be used in the study of high-mass diffraction. We review and analyze the relation between these two versions. We discuss some implications for the BK equation. In the second part of our paper we extend this analysis to the pomeron-odderon-odderon vertex.
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    URL: http://dx.doi.org/10.1140/epjc/s2005-02152-x
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    New method to extract the neutron-electron scattering length (2005)
    Springer
    The European physical journal 40 (2005), S. 473-477 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. A novel method to extract the neutron-electron scattering length b ne from the precise neutron scattering data measured for a noble gas at several different densities n is proposed. The main point of this method is dividing the experimental data into two parts: the first, nearly proportional to n, corresponding to diffraction on neighboring atoms and the second one, a small contribution of n, e scattering independent on n. The proposed technique is demonstrated using the structure factor S(q) for gaseous krypton.
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    Final results from phase II of the Mainz neutrino mass searchin tritium ${\beta}$ decay (2005)
    Springer
    The European physical journal 40 (2005), S. 447-468 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. This paper reports on the improved Mainz experiment on tritium $\beta$ spectroscopy which yields a 10 times higher signal to background ratio than before. The main experimental effects and systematic uncertainties have been investigated in side experiments, and possible error sources have been eliminated. Extensive data taking took place in the years 1997 to 2001. A residual analysis of the data sets yields for the square of the electron antineutrino mass the final result of $m^2(\nu_e) = (-0.6 \pm 2.2_{\mathrm{{stat}}} \pm 2.1_{\mathrm{{syst}}})$ eV2/c4. We derive an upper limit of $m(\nu_e)\leq 2.3$ eV/c2 at 95% confidence level for the mass itself.
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    URL: http://dx.doi.org/10.1140/epjc/s2005-02139-7
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    Polarized forward-backward asymmetries of leptonsin $B_s \rightarrow \ell^ + \ell^- \gamma$ decay (2005)
    Springer
    The European physical journal 40 (2005), S. 505-514 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Polarized forward-backward asymmetries in the $B_s \rightarrow \ell^ + \ell^- \gamma$ decay are calculated using the most general, model independent form of the effective Hamiltonian, including all possible forms of interactions. The dependencies of the asymmetries on new Wilson coefficients are investigated. The detectability of the asymmetries at LHC is discussed.
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    Neutron and light-charged-particle productions in proton-induced reactions on 208Pb at 62.9 MeV (2005)
    Springer
    The European physical journal 23 (2005), S. 49-60 
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    ISSN: 1434-601X
    Keywords: 27.80.+w 190 ⩽ A ⩽ 219 ; 25.40.-h Nucleon-induced reactions ; 25.40.Sc Spallation reactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Neutrons and light charged particles produced in 62.9MeV proton-induced reactions on 208Pb were measured during a single experiment performed at the CYCLONE facility in Louvain-la-Neuve (Belgium). Two independent experimental set-ups were used to extract double differential cross-sections for neutrons, protons, deuterons, tritons, 3He and alpha-particles. Charged particles were detected using a set of Si- Si- CsI telescopes from 25° to 155°, by step of 10 degrees. Neutrons were measured using shielded DeMoN counters, liquid NE213 scintillators, at 24°, 35°, 55°, 80° and 120°. These data allowed the determination of angle differential, energy differential and total production cross-sections. A comparison with theoretical calculations (MCNPX, FLUKA and TALYS) has been performed. It shows that the neutron and proton production rates are well predicted by MCNPX, using the INCL4 option. All the other codes underestimate the neutron production whereas they overestimate the proton one. For composite particles, which represent 17% of the charged particle total reaction cross-section, neither the shape nor the amplitude of the cross-sections are correctly predicted by the models.
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    Levels in 127La fed by the 127Ce beta-decay (2005)
    Springer
    The European physical journal 23 (2005), S. 33-39 
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    ISSN: 1434-601X
    Keywords: 23.20.Lv γ transitions and level energies ; 27.60.+j 90 ⩽ A ⩽ 149
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The low-lying levels in 127La have been studied through the β-decay of 127Ce ( T1/2 = 29s) produced by bombarding a natMo target with a 185-MeV 35Cl beam. Reaction products were on-line mass-separated, and γ-ray singles and γ-γ coincidence measurements were performed. Conversion electrons were also measured and multipolarities of transitions have been derived. The half-life of the 210.9-keV level was determined to be (1.9±0.3)ns by the β-γ delayed coincidence technique. The level scheme obtained has been compared with calculations based on the Nilsson model.
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    Measurement of the πmeson polarizabilities via the γp → γπ+n reaction (2005)
    Springer
    The European physical journal 23 (2005), S. 113-127 
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    ISSN: 1434-601X
    Keywords: 12.38.Qk Experimental tests ; 13.40.-f Electromagnetic processes and properties ; 13.60.Le Meson production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. An experiment on the radiative π{+}-meson photoproduction from the proton ( γp → γπ{+}n) was carried out at the Mainz Microtron MAMI in the kinematic region 537MeV 〈 Eγ 〈 817MeV, 140°≤ $ \theta_{{\gamma \gamma ^{\prime }}}^{{{{\rm cm}}}}$ ≤180°. The π{+}-meson polarizabilities have been determined from a comparison of the data with the predictions of two different theoretical models, the first one being based on an effective pole model with pseudoscalar coupling while the second one is based on diagrams describing both resonant and nonresonant contributions. The validity of the models has been verified by comparing the predictions with the present experimental data in the kinematic region where the pion polarizability contribution is negligible ( s1 〈 5mπ2) and where the difference between the predictions of the two models does not exceed 3%. In the region, where the pion polarizability contribution is substantial ( 5 〈 s1/mπ2 〈 15, -12 〈 t/mπ2 〈 - 2), the difference $\ensuremath{(\alpha -\beta )_{\pi^{+}}}$ of the electric (α) and the magnetic (β) polarizabilities has been determined. As a result we find $\ensuremath{(\alpha -\beta )_{\pi^{+}}=(11.6\pm 1.5_{{\rm stat}}\pm 3.0_{{\rm syst}}\pm 0.5_{{\rm mod}})\times 10^{-4}{}{\rm fm^{3}}}$ . This result is at variance with recent calculations in the framework of chiral perturbation theory.
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    On kaonic deuterium. Quantum field-theoretic and relativistic covariant approach (2005)
    Springer
    The European physical journal 23 (2005), S. 79-111 
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    ISSN: 1434-601X
    Keywords: 11.10.Ef Lagrangian and Hamiltonian approach ; 11.55.Ds Exact S matrices ; 13.75.Gx Pion-baryon interactions ; 36.10.-k Exotic atoms and molecules (containing mesons, muons, and other unusual particles)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We study kaonic deuterium, the bound K-d state AK d. Within a quantum field-theoretic and relativistic covariant approach we derive the energy level displacement of the ground state of kaonic deuterium in terms of the amplitude of K-d scattering for arbitrary relative momenta. Near threshold our formula reduces to the well-known DGBT formula. The S-wave amplitude of K-d scattering near threshold is defined by the resonances Λ(1405), Σ(1750) and a smooth elastic background, and the inelastic channels K-d → NY and K-d → NYπ, where Y = Σ±,Σ{0} and Λ{0}, where the final-state interactions play an important role. The Ericson-Weise formula for the S-wave scattering length of K-d scattering is derived. The total width of the energy level of the ground state of kaonic deuterium is estimated using the theoretical predictions of the partial widths of the two-body decays AKd → NY and experimental data on the rates of the NY pair production in the reactions K-d → NY. We obtain Γ{1s} = (630±100)eV. For the shift of the energy level of the ground state of kaonic deuterium we predict ε{1s} = (325±60)eV.
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    Coexisting oblate and strongly triaxial structures in 191Pt (2005)
    Springer
    The European physical journal 23 (2005), S. 69-78 
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    ISSN: 1434-601X
    Keywords: 29.30.Kv X- and γ-ray spectroscopy ; 23.20.Lv γ transitions and level energies ; 21.60.Ev Collective models ; 27.80.+w 190 ⩽ A ⩽ 219
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Excited states in 191Pt have been populated using the reaction 186W + 11B at 85MeV beam energy. Gamma-ray coincidences were measured using the EUROGAM-II spectrometer array. The level scheme has been extended considerably. Evidence for favoured structures of highly triaxial shape with γ ∼ -90° coexisting with oblate structures has been obtained by comparison with total Routhian surface and cranked shell model calculations. The presence of proton excitations in both positive- and negative-parity states has been confirmed.
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    Spallation neutron spectrum on a massive lead/paraffin target irradiated with 1 GeV protons (2005)
    Springer
    The European physical journal 23 (2005), S. 61-68 
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    ISSN: 1434-601X
    Keywords: 28.41.Kw Radioactive wastes, waste disposal ; 29.30.Kv X- and γ-ray spectroscopy ; 02.70.Uu Applications of Monte Carlo methods ; 07.05.Fb Design of experiments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The gamma-ray spectra emitted by decaying of residual nuclei produced by spallation neutrons in (n, xn), (n, xnyp), (n, p), (n, γ) reactions with activation threshold detectors, i.e. 209Bi, 197Au, 59Co, 115In, 232Th, were measured in the Laboratory of Nuclear Problems (LNP), JINR, Dubna, Russia. Spallation neutrons were generated by bombarding a 20 cm long cylindrical lead target with 8 cm diameter surrounded by a 6 cm thick layer of paraffin moderator with 1 GeV proton beam from the NUCLOTRON accelerator. Reaction rates and a spallation neutron spectrum were measured and compared with CASCADE code calculations.
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    Halo or skin in the excited states of some light mirror nuclei (2005)
    Springer
    The European physical journal 23 (2005), S. 11-17 
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    ISSN: 1434-601X
    Keywords: 21.10.Gv Mass and neutron distributions ; 21.60.Jz Hartree-Fock and random-phase approximations ; 21.10.Dr Binding energies and masses ; 27.20.+n 6 ⩽ A ⩽ 19
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The properties of three pairs of mirror nuclei 13N- 13C, 15N- 15O and 21Na- 21Ne (these mirror nuclei are all made of a good inert core plus an unpaired valence nucleon) are investigated by using the nonlinear relativistic mean-field (RMF) theory. It is found that the calculated binding energies with two different parameter sets are very close to the experimental ones for both the ground states and the excited states except for the large deformed nuclei. The calculations show that the 2s1/2 excited states of 15N and of 21Na are both weakly bound with a proton halo and a proton skin (or a pigmy proton skin), respectively. In addition, the 1d5/2 excited state of 13C and the 2s1/2 excited state of 15O are also weakly bound with a neutron skin, respectively. The ratio of the valence nucleon radius to matter radius is deduced and it can be regarded as an additional criterion for the existence of exotic structure. The unbound 2s1/2 and 1d5/2 excited states of 13N are also discussed.
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    Search for spontaneous transition of nuclei to a superdense state (2005)
    Springer
    The European physical journal 23 (2005), S. 7-10 
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    ISSN: 1434-601X
    Keywords: 21.10.Ft Charge distribution ; 21.10.-k Properties of nuclei; nuclear energy levels ; 21.65.+f Nuclear matter ; 29.40.Mc Scintillation detectors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We report the results of an experimental search for spontaneous transition of nuclei from ordinary to superdense state in NaI(Tl). New limits on the superdense-state parameters are presented.
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    General survey of polarization observables in deuteron electrodisintegration (2005)
    Springer
    The European physical journal 23 (2005), S. 147-190 
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    ISSN: 1434-601X
    Keywords: 21.45.+v Few-body systems ; 24.70.+s Polarization phenomena in reactions ; 25.30.Fj Inelastic electron scattering to continuum ; 13.40.-f Electromagnetic processes and properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Polarization observables in inclusive and exclusive electrodisintegration of the deuteron using a polarized beam and an oriented target are systematically surveyed using the standard nonrelativistic framework of nuclear theory but with leading-order relativistic contributions included. The structure functions and the asymmetries corresponding to the various nucleon polarization components are studied in a variety of kinematic regions with respect to their sensitivity to realistic NN-potential models, to subnuclear degrees of freedom in terms of meson exchange currents, isobar configurations and to relativistic effects in different kinematical regions, serving as a benchmark for a test of present standard nuclear theory with effective degrees of freedom.
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    P-wave charmonium decays into baryon and antibaryon pairs in quark pair creation model (2005)
    Springer
    The European physical journal 23 (2005), S. 129-133 
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    ISSN: 1434-601X
    Keywords: 13.25.Gv Decays of J/ψ, ϒ, and other quarkonia ; 12.39.Jh Nonrelativistic quark model ; 14.20.Jn Hyperons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. A simple quark pair creation model is introduced to study exclusive decays of χ{c_J} into baryon-antibaryon pairs. With this simple model, some exclusive decay processes, for example, χ{c0} → B¯ (B = Λ,Σ0,Ξ-) are investigated and their decay widths are evaluated by inclusion of the properties of outgoing baryons, and the results show that the strengthened decay channels χ{c_J} → Λ¯(J = 0, 2) are easily understood by considering only the color singlet contribution of P-wave charmonium.
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    Beta-decay studies of neutron-rich Sc- Cr nuclei (2005)
    Springer
    The European physical journal 23 (2005), S. 41-48 
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    ISSN: 1434-601X
    Keywords: 27.50.+e 59 ⩽ A ⩽ 89 ; 23.40.-s β decay; double β decay; electron and muon capture ; 21.60.Cs Shell model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The neutron-rich nuclei          2157, 58Sc,          2258-60Ti,          2360-63V,          2462-66Cr have been produced at Ganil via interactions of a 61.8A MeV 76Ge beam with a 58Ni target. Beta-decay studies have been performed using combined β- and γ-ray spectroscopy. Half-lives have been determined and β-decay schemes are proposed for 58Ti, 61V and 62Cr. From these studies, new hints for the existence of β-decaying isomers in 60V and in 62Mn are provided. These results are compared to shell model calculations. The role of the πf7/2- νf5/2 proton-neutron interaction is examined through its influence on the lifetime values.
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    Emission of unbound 8Be and 12C * (0+2) clusters in compound nucleus reactions (2005)
    Springer
    The European physical journal 23 (2005), S. 19-31 
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    ISSN: 1434-601X
    Keywords: 21.60.Gx Cluster models ; 23.90.+w Other topics in radioactive decay and in-beam spectroscopy ; 25.70.Gh Compound nucleus ; 25.70.Pq Multifragment emission and correlations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We have studied the emission of light unbound clusters, 8Be and 12C * (0+2), in the reactions 18O + 13C →{31} Si →{23} Ne + 8Be and 28Si + 24Mg →{52} Fe →{40} Ca + 12C * (0+2). The γ-ray spectra obtained in coincidence with 8Be and 12C * (0+2) emission have been studied relative to the statistical emission of two or three α-particles. The angular-momentum-to-energy balance of the cluster emission is compared with that of multiple-α emission. The properties of the energy spectra of the binary process and the population of the residual nuclei by cluster emission are discussed. It is observed that cluster emission carries away less excitation energy on average than the sequential emission of the individual components.
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    Three-step laser excitation of the 6p3/2ns, nd, ng autoionizing Rydberg levels via the 6p5f 1/2[5/2]2 level of lead (2005)
    Springer
    The European physical journal 32 (2005), S. 271-276 
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    ISSN: 1434-6079
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Odd parity autoionizing Rydberg levels of atomic lead in the energy region above the 6p1/2 ionization threshold have been investigated using three-step laser excitation in conjunction with an atomic beam apparatus. The 6p3/2ns (J = 1, 2), 6p3/2nd (J = 1, 2, 3) and 6p3/2ng (J = 2, 3) levels have been observed from the 6p5f 1/2[5/2]2 intermediate level. Energy values and FWHM of forty levels belonging to the 6p3/2ns, 6p3/2nd and 6p3/2ng configurations are presented. Six levels based on the 6p3/2ng (5, 13 ≤n ≤15) configurations and three levels attached to the 6p3/28d configuration are reported for the first time. The present study of the low-lying autoionizing levels attached to the 6p3/25g (J = 2, 3) configuration completes the series adjacent to the 6p1/2 limit.
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    Dynamics of a charged particle in a linearly polarized traveling wave (2005)
    Springer
    The European physical journal 32 (2005), S. 361-376 
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    ISSN: 1434-6079
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The basic physical processes in laser-matter interaction, up to $10^{17}~{\rm W/cm}^2$ (for a neodymium laser) are now well understood, on the other hand, new phenomena evidenced in PIC code simulations have to be investigated above $10^{18}~{\rm W/cm}^2$ . Thus, the relativistic motion of a charged particle in a linearly polarized homogeneous electromagnetic wave is studied, here, using the Hamiltonian formalism. First, the motion of a single particle in a linearly polarized traveling wave propagating in a non-magnetized space is explored. The problem is shown to be integrable. The results obtained are compared to those derived considering a cold electron plasma model. When the phase velocity is close to c, it is shown that the two approaches are in good agreement during a finite time. After this short time, when the plasma response is taken into account no chaos take place at least when considering low densities and/or high wave intensities. The case of a charged particle in a traveling wave propagating along a constant homogeneous magnetic field is then considered. The problem is shown to be integrable when the wave propagates in vacuum. The existence of a synchronous solution is shown very simply. In the case when the wave propagates in a low density plasma, using a simplifying Lorentz transformation, it is shown that the system can be reduced to a time-dependent system with two degrees of freedom. The system is shown to be nonintegrable, chaos appears when a secondary resonance and a primary resonance overlap. Finally, stochastic instabilities are studied by considering the motion of one particle in a very high intensity wave perturbed by one or two low intensity traveling waves. Resonances are identified and conditions for resonance overlap are studied.
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    Smoothed Wigner functions: a tool to resolve semiclassical structures (2005)
    Springer
    The European physical journal 32 (2005), S. 355-359 
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    ISSN: 1434-6079
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The Wigner and Husimi distributions are the usual phase space representations of a quantum state. The Wigner distribution has structures of order ħ2. On the other hand, the Husimi distribution is a Gaussian smearing of the Wigner function on an area of size ħ and then, it only displays structures of size ħ. We have developed a phase space representation which results a Gaussian smearing of the Wigner function on an area of size ħσ, with σ≥1. Within this representation, the Husimi and Wigner functions are recovered when σ=1 and $ \sigma \gtrsim 2 $ respectively. We treat the application of this intermediate representation to explore the semiclassical limit of quantum mechanics. In particular we show how this representation uncover semiclassical hyperbolic structures of chaotic eigenstates.
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    Time-resolved homodyne characterization of individual quadrature-entangled pulses (2005)
    Springer
    The European physical journal 32 (2005), S. 391-396 
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    ISSN: 1434-6079
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We describe a simple and efficient set-up to generate and characterize femtosecond quadrature-entangled pulses. Quantum correlations equivalent to about 2.5 dB squeezing are efficiently and easily reached using the non-degenerate parametric amplification of femtosecond pulses through a single-pass in a thin (100 μm) potassium niobate crystal. The entangled pulses are then individually sampled to characterize the non-separability and the entropy of formation of the states. The complete experiment is analysed in the time-domain, from the pulsed source of quadrature entanglement to the time-resolved homodyne detection. This particularity allows for applications in quantum communication protocols using continuous-variable entanglement.
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    Features of ball lightning stability (2005)
    Springer
    The European physical journal 32 (2005), S. 383-389 
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    ISSN: 1434-6079
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. An electrostriction optical effect, effect of separation of a gas mixture in a field of an intense light and effect of a violation of homogeneity of plasma by an intense light are considered. It is shown that the first effect shows itself after penetration of Ball Lightning through glass panes and the last two ones are the most favorable for appearance Ball Lightning. The density of the energy and conditions of Ball Lightning stability are analyzed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjd/e2004-00198-7
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    A density functional study of small AlxOy (x,y=1-4) clusters and their thermodynamic properties (2005)
    Springer
    The European physical journal 32 (2005), S. 329-337 
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    ISSN: 1434-6079
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We report thermodynamic properties of small aluminium oxide clusters of mixed stoichiometric ratio AlxOy (x,y=1-4). The rigid rotator-harmonic oscillator approximation is used to calculate the partition function as it is generally applied in thermodynamic studies of polyatomic molecules. The molecular data used to set up the partition functions were computed by density functional techniques employing the BP86 gradient corrected exchange correlation functional. Thereby, the results of three species viz. AlO4, Al4O2, and Al4O3 previously not reported in the literature are included in this study. Equilibrium geometric parameters, energies, selected harmonic vibrational wave numbers of energetically low–lying stationary points are presented along with corresponding absorption coefficients. The resulting thermodynamic functions of aluminium oxides are consistent with the JANAF thermochemical data compilation. These functions are used to determine the temperature dependent chemical equilibrium partial pressure distributions for different aluminium to oxygen ratios.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjd/e2005-00026-8
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    Diffraction of three-dimensional beams in uniaxial media (2005)
    Springer
    The European physical journal 32 (2005), S. 377-381 
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    ISSN: 1434-6079
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Within here we make an analysis of two and three-dimensional beams synthesized by extraordinary waves that propagate in uniaxial media. A relation between the geometric place of the first interference maxima and the energy flow direction is established. In addition, we determine that three-dimensional extraordinary symmetrical beams can be obtained from two two-dimensional ones that are not to be necessarily orthogonal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjd/e2004-00181-4
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    Obtaining colder ensembles of free clusters by using evaporation and recoil (2005)
    Springer
    The European physical journal 32 (2005), S. 339-345 
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    ISSN: 1434-6079
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We describe a theoretical model which treats the effects of evaporation-induced recoil on the mass and temperature distributions of a collimated beam of small neutral clusters emitted by a hot-nozzle source. The model incorporates two important consequences of in-flight cluster fragmentation processes. One is the well-known statistical evaporation of atoms and dimers accompanied by cluster size redistribution and cooling, and the other is the accompanying mechanical recoil of the fragments. We predict that the filtering effect introduced by cluster recoil can be used to an advantage by separating out the off-axis cluster population. This fraction will have a significantly narrower and colder distribution of internal temperatures than the on-axis ensemble.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjd/e2004-00188-9
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  • 196
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    Excessive hydrogen and deuterium Balmer lines broadening in a hollow cathode glow discharges (2005)
    Springer
    The European physical journal 32 (2005), S. 347-354 
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    ISSN: 1434-6079
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Results of a Doppler spectroscopy study of hydrogen and deuterium Balmer lines in the stainless steel and copper hollow cathode glow discharge, operated in pure hydrogen, deuterium and mixtures of inert gases with hydrogen, are reported. For all gases and gas mixtures plasma observations perpendicular to electric field revealed the excessively large Doppler broadening. By changing mode of glow discharge operation, the Doppler broadened line profiles in helium-hydrogen mixture are recorded parallel to the discharge electric field as well. The excessively broadened part of the Hα line profile is shifted towards blue or red wavelength by changing the direction of electric field vector. The presence of large excessive Balmer lines broadening in pure hydrogen and in its gas mixture with neon as well as shifting of the excessively broadened part of line profile by means of electric field is in contradiction with the resonance transfer model proposed by Mills et al. in several publications, see e.g. [IEEE Trans. Plasma Sci. 31, 338 (2003)].  
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjd/e2004-00192-1
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    Radiative lifetimes of some excited states of neutral xenon (2005)
    Springer
    The European physical journal 32 (2005), S. 285-288 
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    ISSN: 1434-6079
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The radiative lifetimes of ten levels belonging to the nf (n=4-7) and three levels belonging to the ns (n=8,9) configuration of XeI have been measured using the high frequency deflection technique together with a delayed coincidence single-photon counting arrangement. Lifetimes of some of the levels have been measured for the first time. The results have been compared with other experimental and theoretical values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjd/e2005-00002-4
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    The threshold electron impact spectrum of H2O (2005)
    Springer
    The European physical journal 32 (2005), S. 319-328 
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    ISSN: 1434-6079
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The threshold electron spectrum of H2 O was obtained using a high resolution electron impact spectrometer combined with the penetrating field method for scattered electrons with energies close to zero eV. The valence, triplet Rydberg states, as well as the resonances were identified and are discussed in the energy region 5.2–14.3 eV. The threshold spectrum confirms the influence of resonances on the enhancement of the intensity of some Rydberg states above 10 eV. The vibrational spacing of the observed transitions of the Rydberg states indicates that the water molecule is excited in the symmetric stretching mode.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjd/e2005-00001-5
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    Insights into positron annihilation lifetime spectroscopy by molecular dynamics simulations (2005)
    Springer
    The European physical journal 32 (2005), S. 289-297 
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    ISSN: 1434-6079
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The relationship between free-volume properties measured from positron annihilation lifetime spectroscopy (PALS) and calculated from molecular dynamics simulations has been investigated for glassy and liquid glycerol in the temperature range 150–400 K. A virtual probing procedure has been developed to retrieve information on the basic free-volume properties of the simulated microstructures, i.e. mean cavity volume and free-volume cavity fractions. Our data leads us to infer on the occurrence of experimentally non-detectable small cavities with mean equivalent radius of 1.8–1.9 Å between 250 and 275 K. The size of these limiting cavities is found to be temperature dependent, being smaller at low temperatures. At high temperatures, above a characteristic PALS temperature Tb2L , the formation of very large cavities is predicted. This finding suggests that, when the dimension of the holes in the system exceeds a given value, the PALS measurements become unable to catch the complete structural information and phenomena of dynamical origin enter into play in the PALS signal decay. The calculated number of cavities is found to be almost independent on the temperature from the glassy up to the liquid phase, thus furnishing a certain support to theoretical models proposed to evaluate the free-volume cavity fractions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjd/e2005-00015-y
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    Thermal entanglement in two qutrits system (2005)
    Springer
    The European physical journal 32 (2005), S. 409-412 
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    ISSN: 1434-6079
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The thermal entanglement in a two-qutrit system with two spins coupled by exchange interaction is investigated in terms of the measure of entanglement called “negativity”. It is found that the thermal entanglement is present and evolvements symmetrically between both ferromagnetic and antiferromagnetic exchange couplings with the temperature. Moreover the critical temperature at which the negativity vanishes increases with the exchange coupling constant J. From the temperature and magnetic field dependences we demonstrate that the temperature and the magnetic field can affect the feature of the thermal entanglement significantly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjd/e2004-00194-y
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