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  • Springer  (90,625)
  • 2015-2019
  • 2010-2014  (52,460)
  • 2005-2009  (38,165)
  • 2010  (52,460)
  • 2005  (38,165)
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  • 2015-2019
  • 2010-2014  (52,460)
  • 2005-2009  (38,165)
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  • 1
    Unknown
    Trusted computing platforms : design and applications (2005)
    New York : Springer
    Details
    Keywords: Computer engineering. ; Computer security. ; Electronic data processing, Distributed processing.
    Pages: xx, 239 p.
    ISBN: 0-387-23917-0
    URL: http://www.netLibrary.com/urlapi.asp?action=summary&v=1&bookid=128476
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  • 2
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    Gravity, geoid and space missions : GGSM 2004 IAG international symposium, Porto, Portugal, August 30 - September 3, 2004 (2005)
    Springer
    In:  International Association of Geodesy Symposia
    Details
    Publication Date: 2020-02-12
    Description: The lAG International Symposium on Gravity, Geoid, and Space Missions 2004 (GGSM2004) was lield in the beautiful city of Porto, Portugal, from 30 August to 3 September 2004. This symposium encompassed the themes of Commission 2 (Gravity Field) of the newly structured lAG, as well as interdisciplinary topics related to geoid and gravity modeling, with special attention given to the current and planned gravi- dedicated satellite missions. The symposium also followed in the tradition of mid-term meetings that were held between the quadrennial joint meetings of the International Geoid and Gravity Commissions. The previous mid-term meetings were the International Symposia on Gravity, Geoid, and Marine Geodesy (Tokyo, 1996), and Gravity, Geoid, and Geodynamics (Banff, 2000). GGSM2004 aimed to bring together scientists from different areas in the geosciences, working with gravity and geoid related problems, both from the theoretical and practical points of view. Topics of interest included the integration of heterogeneous data and contributions from satellite and airborne techniques to the study of the spatial and temporal variations of the gravity field. In addition to the special focus on the CHAMP, GRACE, and GOCE satellite missions, attention was also directed toward projects addressing topographic and ice field mapping using SAR, LIDAR, and laser altimetry, as well as missions and studies related to planetary geodesy.
    Language: English
    Type: info:eu-repo/semantics/book
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  • 3
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    Sciences of Geodesy - I : advances and future directions (2010)
    Springer
    Details
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/book
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  • 4
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    Earth Observation with CHAMP : Results from Three Years in Orbit (2005)
    Springer
    Details
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/book
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  • 5
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    Stress field of the earth's crust (2010)
    Springer
    Details
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/book
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  • 6
    Electronic Resource
    Electronic Resource
    Beta-decay studies of neutron-rich Sc- Cr nuclei (2005)
    Springer
    The European physical journal 23 (2005), S. 41-48 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epja/i2004-10068-x
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  • 7
    Electronic Resource
    Electronic Resource
    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 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epja/i2004-10031-y
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  • 8
    Electronic Resource
    Electronic Resource
    Emission of unbound 8Be and 12C * (0+2) clusters in compound nucleus reactions (2005)
    Springer
    The European physical journal 23 (2005), S. 19-31 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epja/i2004-10071-3
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  • 9
    Electronic Resource
    Electronic Resource
    On kaonic deuterium. Quantum field-theoretic and relativistic covariant approach (2005)
    Springer
    The European physical journal 23 (2005), S. 79-111 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epja/i2004-10055-3
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  • 10
    Electronic Resource
    Electronic Resource
    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 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epja/i2004-10069-9
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  • 11
    Electronic Resource
    Electronic Resource
    The neutron decay retardation spectrometer aSPECT: Electromagnetic design and systematic effects (2005)
    Springer
    The European physical journal 23 (2005), S. 135-146 
    Details
    ISSN: 1434-601X
    Keywords: 23.40.-s Beta decay; double beta decay; electron and muon capture ; 13.30.-a Decays of baryons ; 12.15.Hh Determination of Kobayashi-Maskawa matrix elements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The apparatus described here, aSPECT, will be used for a measurement of the neutrino-electron angular correlation coefficient a in the decay of free neutrons. The idea of the aSPECT spectrometer is to measure the integrated proton energy spectrum very accurately using an energy filter by electrostatic retardation and magnetic adiabatic collimation. The main ideas of the spectrometer are presented, followed by an explanation of the adiabatic transmission function. Details of the superconducting coil and of the electrode system are given, as well as a discussion of the most important systematic effects: magnetic field and electrostatic potential inhomogeneities, deviation from adiabatic motion, scattering in the residual gas, background, Doppler effect, edge effect, and detector efficiency. Using this spectrometer, the parameter a is planned to be measured with an absolute experimental uncertainty of δa ≈ 3 . 10-4, from which the axial vector to vector coupling constant ratio λ can be determined with an accuracy of δλ ≈ 0.001.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epja/i2004-10057-1
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  • 12
    Electronic Resource
    Electronic Resource
    Modeling the pion and kaon form factors in the timelike region (2005)
    Springer
    The European physical journal 39 (2005), S. 41-54 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2004-02064-3
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  • 13
    Electronic Resource
    Electronic Resource
    Longitudinal $\bar{\Lambda}_0$ polarization in heavy-ion collisions as a probe for QGP formation (2005)
    Springer
    The European physical journal 39 (2005), S. 95-99 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2004-02073-2
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  • 14
    Electronic Resource
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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 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2004-02081-2
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  • 15
    Electronic Resource
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    Twisted mass quarks and the phase structure of lattice QCD (2005)
    Springer
    The European physical journal 39 (2005), S. 421-433 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The phase structure of zero temperature twisted mass lattice QCD is investigated. We find strong metastabilities in the plaquette observable in correspondence of which the untwisted quark mass assumes positive or negative values. We provide interpretations of this phenomenon in terms of chiral symmetry breaking and the effective potential model of Sharpe and Singleton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2004-02078-9
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  • 16
    Electronic Resource
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    Jet production in pA and AA collisions in the perturbative QCD pomeron model (2005)
    Springer
    The European physical journal 39 (2005), S. 451-464 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Inclusive cross-sections for gluon jet production are studied numerically in the perturbative QCD pomeron model for pA and central AA collisions at high energies. Two forms for the inclusive cross-sections, with and without emission from the triple pomeron vertex, are compared. The difference was found to reduce to a numerical factor $\sim 0.7\div 0.8$ for momenta below the saturation momentum Q s. Above Q s no difference was found at all. For pA collisions the gluon spectrum was found to be $\sim A^{0.7}$ at momenta k below Q s and $\sim A^{0.9}$ above it. For central AA collisions it was found to be $\sim A$ at momenta k below Q s and $\sim A^{1.1}$ above it. At large k the spectrum goes like $1/k^{2.7\div 3.3}$ , flattening with energy. The multiplicities turned out to be proportional to A 0.7 for pA collisions and A for central AA collisions with a good precision. In the latter case they are becoming more peaked at the center with the growth of energy. Their absolute values are high and grow rapidly with energy in accordance with the high value of the BFKL intercept.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2004-02098-5
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  • 17
    Electronic Resource
    Electronic Resource
    Improved phase space treatment of massive multi-particle final states (2005)
    Springer
    The European physical journal 39 (2005), S. 439-450 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. In this paper the revised Kajantie-Byckling approach and improved phase space sampling techniques for the massive multi-particle final states are presented. The application of the developed procedures to the processes representative for LHC physics indicates the possibility of a substantial simplification of multi-particle phase space sampling while retaining a respectable weight variance reduction and unweighing efficiencies in the event generation process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2004-02105-y
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  • 18
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    Observing higher-dimensional black holes at the LHC (2005)
    Springer
    The European physical journal 39 (2005), S. 503-509 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. A new approach to spacetime proposing the existence of n compactified large extra dimensions predicts the creation of higher-dimensional black holes at the LHC of CERN. In case they form, signatures of such black holes at accelerators would be quite significant and black hole decay products would carry valuable information for particle physics and cosmology. In this study we first make a short theoretical introduction, then present the results of an analysis made on a Monte Carlo simulation modeling black hole production and decay at the LHC. This analysis includes the examination of the lepton case in black hole to Higgs decay channels, reconstruction of the black hole masses, a calculation of the Hawking temperature and a determination of the radiated jets/leptons multiplicity ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2004-02111-1
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  • 19
    Electronic Resource
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    Orbifold compactification and solutions of M-theory from Milne spaces (2005)
    Springer
    The European physical journal 39 (2005), S. 519-524 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. In this paper, we consider solutions and spectral functions of M-theory from Milne spaces with extra free dimensions. Conformal deformations to the metric associated with real hyperbolic space forms are derived. For the three-dimensional case, the orbifold identifications ${\mathrm{SL}}(2,{\mathbb{Z}} + {\mathrm{i}}{\mathbb{Z}})/\{\pm {\mathrm{Id}}\}$ , where Id is the identity matrix, is analyzed in detail. The spectrum of an eleven-dimensional field theory can be obtained with the help of the theory of harmonic functions in the fundamental domain of this group and it is associated with the cusp forms and the Eisenstein series. The supersymmetry surviving for supergravity solutions involving real hyperbolic space factors is briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2005-02117-1
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  • 20
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    Isospin constraints from/on $B \to \pi\pi$ (2005)
    Springer
    The European physical journal 39 (2005), S. 397-409 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The Standard Model constraints on $\alpha$ which can be derived from the $B\rightarrow\pi\pi$ decays are revisited in some depth. As experimental inputs, the $B^0\rightarrow\pi^ + \pi^-$ , $B^ + \rightarrow\pi^ + \pi^0$ decays complemented by the $B^0\rightarrow\pi^0\pi^0$ decays, the CP parameters $S_{\pi\pi}$ and $C_{\pi\pi}$ , and/or the value of $\alpha$ as determined by the global CKM fit are used. The constraints discussed here are model independent in the sense that they rely only on Isospin symmetry, following the Gronau-London proposal. A new bound on $\mathcal{B}^{00}$ and the function $C_{00}(\mathcal{B}^{00})$ are introduced. While another bound applied to BABAR results is shown to imply that $\cos(2\alpha_{\rm eff})$ is negative. The Grossman-Quinn bound is rediscussed. A close form expression is given for $\alpha$ as a function of the measurements. Various scenarios for the future of the isospin analysis are explored. To probe the Standard Model the $(\mathcal{B}^{00},C_{00})$ plane is introduced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2005-02119-y
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  • 21
    Electronic Resource
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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 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    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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    URL: http://dx.doi.org/10.1140/epjc/s2004-02097-6
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  • 22
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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 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    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 $$ A_{\mathrm{FB}}^{{\mathrm{b, 0}}} = 0.0972 \pm 0.0030(\mbox{stat.}) \pm 0.0014(\mbox{syst.}) . $$
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2004-02104-0
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  • 23
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    Effective action and Hawking flux from covariant perturbation theory (2005)
    Springer
    The European physical journal 40 (2005), S. 275-286 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The computation of the radiation flux related to the Hawking temperature of a Schwarzschild black hole or another geometric background is still well-known to be fraught with a number of delicate problems. In spherical reduction, as shown by one of the present authors (Kummer) with Vassilevich, the correct black body radiation follows when two “basic components” (conformal anomaly and a “dilaton” anomaly) are used as input in the integrated energy-momentum conservation equation. The main new element in the present work is the use of a quite different method, the covariant perturbation theory of Barvinsky and Vilkovisky, to establish directly the full effective action which determines these basic components. In the derivation of Kummer and Vassilevich the computation of the dilaton anomaly implied one potentially doubtful intermediate step which can be avoided here. Moreover, the present approach also is sensitive to IR (renormalization) effects. We realize that the effective action naturally leads to expectation values in the Boulware vacuum which, making use of the conservation equation, suffice for the computation of the Hawking flux in other quantum states, in particular for the relevant Unruh state. Thus, a rather comprehensive discussion of the effects of (UV and IR) renormalization upon radiation flux and energy density is possible.
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    URL: http://dx.doi.org/10.1140/epjc/s2005-02129-9
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  • 24
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    Correlator of heavy-quark currents at small q 2 in the large- $\beta_0$ limit (2005)
    Springer
    The European physical journal 40 (2005), S. 157-164 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The correlator of vector heavy-quark currents at small q 2 is considered in the large- $\beta_0$ limit. The leading IR renormalon ambiguity of the sum of the perturbative series is canceled by the UV renormalon ambiguity of the gluon condensate. The asymptotic behavior of the perturbative series is obtained in a model-independent way, up to a single unknown normalization factor. Gluon-virtuality distribution functions for the perturbative correction are calculated.
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    The difference between n-dimensional regularization and n-dimensional reduction in QCD (2005)
    Springer
    The European physical journal 40 (2005), S. 199-203 
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    Topics: Physics
    Notes: Abstract. We discuss the difference between n-dimensional regularization and n-dimensional reduction for processes in QCD which have an additional mass scale. Examples are heavy flavor production in hadron-hadron collisions or on-shell photon-hadron collisions where the scale is represented by the mass m. Another example is electroproduction of heavy flavors where we have two mass scales given by m and the virtuality of the photon $\smash[b]{Q = \sqrt{-q^2}}$ . Finally we study the Drell-Yan process where the additional scale is represented by the virtuality $\smash[t]{Q = \sqrt{q^2}}$ of the vector boson ( $\gamma^*, W, Z$ ). The difference between the two schemes is not accounted for by the usual oversubtractions. There are extra counter terms which multiply the mass scale dependent parts of the Born cross sections. In the case of the Drell-Yan process it turns out that the off-shell mass regularization agrees with n-dimensional regularization.
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    Measurements of the charge asymmetry of the Dalitz plot parameters for $K^{\pm}\to\pi^{\pm}\pi^0\pi^0$ decays (2005)
    Springer
    The European physical journal 40 (2005), S. 343-347 
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    Notes: Abstract. The charge asymmetry of the g, h, and k Dalitz plot parameters for ${K^{\pm}\rightarrow \pi^{\pm} \pi^{0} \pi^{0}}$ decays has been measured with 35 GeV/c hadron beams at the 70 GeV IHEP accelerator. The g, h, and k values obtained appear to be identical for $K^{\pm}$ decays within the errors quoted. In particular, the charge asymmetry A g = (g + – g -)/(g + + g -) of the slope g is equal to ${(0.2 \pm 1.9)\cdot 10^{-3}}$ .
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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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    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.
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    H/A Higgs mixing in CP-noninvariant supersymmetric theories (2005)
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    The European physical journal 40 (2005), S. 555-564 
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    Notes: Abstract. For large masses, the two heavy neutral Higgs bosons are nearly degenerate in many 2-Higgs doublet models, and particularly in supersymmetric models. In such a scenario the mixing between the states can be very large if the theory is CP-noninvariant. We analyze the formalism describing this configuration, and we point to some interesting experimental consequences.
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    Study of the neutron quantum states in the gravity field (2005)
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    The European physical journal 40 (2005), S. 479-491 
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    Notes: Abstract. We have studied neutron quantum states in the potential well formed by the earth’s gravitational field and a horizontal mirror. The estimated characteristic sizes of the neutron wave functions in the two lowest quantum states correspond to expectations with an experimental accuracy. A position-sensitive neutron detector with an extra-high spatial resolution of $\sim 2 \mathrm{\mu} $ m was developed and tested for this particular experiment, to be used to measure the spatial density distribution in a standing neutron wave above a mirror for a set of some of the lowest quantum states. The present experiment can be used to set an upper limit for an additional short-range fundamental force. We studied methodological uncertainties as well as the feasibility of improving further the accuracy of this experiment.
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    Optimal observables and phase-space ambiguities (2005)
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    The European physical journal 40 (2005), S. 497-503 
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    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.
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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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    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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    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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    Exclusive semileptonic rare decays $B \to K^{(*)} l^ + l^-$ in a SUSY SO(10) GUT (2005)
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    The European physical journal 40 (2005), S. 565-577 
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    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.
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    Corrections to quark asymmetries at LEP (2005)
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    The European physical journal 40 (2005), S. 493-496 
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    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.
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    Probing the perturbative NLO parton evolution in the small-x region (2005)
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    The European physical journal 40 (2005), S. 515-517 
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    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.
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    The QCD pomeron in ultraperipheral heavy ion collisions: IV. Photonuclear production of vector mesons (2005)
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    The European physical journal 40 (2005), S. 519-529 
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    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.
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    Pomeron vertices in perturbative QCD in diffractive scattering (2005)
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    The European physical journal 40 (2005), S. 419-433 
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    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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    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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    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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    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)
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    The European physical journal 43 (2005), S. 187-193 
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    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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    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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    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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    Photon events with missing energy in e + e- collisions at $\sqrt{s} = {}$ 130 to 209 GeV (2005)
    Springer
    The European physical journal 38 (2005), S. 395-411 
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    Notes: Abstract. The production of single- and multi-photon events has been studied in the reaction $e^ + e^-\rightarrow\gamma(\gamma) + invisible \quad particles$ . The data collected with the DELPHI detector during the years 1999 and 2000 at centre-of-mass energies between 191 GeV and 209 GeV was combined with earlier data to search for phenomena beyond the Standard Model. The measured number of light neutrino families was consistent with three and the absence of an excess of events beyond that predicted by the Standard Model processes was used to set limits on new physics. Both model-independent searches and searches for new processes predicted by supersymmetric and extra-dimensional models have been made. Limits on new non-standard model interactions between neutrinos and electrons were also determined.
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    A systematic study of neutrino mixing and CP-violationfrom lepton mass matrices with six texture zeros (2005)
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    The European physical journal 38 (2005), S. 495-510 
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    Notes: Abstract. We present a systematic study of 400 combinations of the charged lepton and neutrino mass matrices with six vanishing entries or texture zeros. Only 24 of them, which can be classified into a few distinct categories, are found to be compatible with current neutrino oscillation data at the $3\sigma$ level. A peculiar feature of the lepton mass matrices in each category is that they have the same phenomenological consequences. Taking account of a simple seesaw scenario for six parallel patterns of the charged lepton and Dirac neutrino mass matrices with six zeros, we show that it is possible to fit the experimental data at or below the $2\sigma$ level. In particular, the maximal atmospheric neutrino mixing can be reconciled with a strong neutrino mass hierarchy in the seesaw case. Numerical predictions are also obtained for the neutrino mass spectrum, flavor mixing angles, CP-violating phases and effective masses of the tritium beta decay and the neutrinoless double beta decay.
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    Leading-particle suppression in high energy nucleus-nucleus collisions (2005)
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    The European physical journal 38 (2005), S. 461-474 
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    Notes: Abstract. Parton energy loss effects in heavy-ion collisions are studied with the Monte Carlo program PQM (Parton Quenching Model) constructed using the BDMPS quenching weights and a realistic collision geometry. The merit of the approach is that it contains only one free parameter that is tuned to the high-p t nuclear modification factor measured in central Au-Au collisions at $\sqrt{s_{\rm NN}} = 200$ GeV. Once tuned, the model is consistently applied to all the high-p t observables at 200 GeV: the centrality evolution of the nuclear modification factor, the suppression of the away-side jet-like correlations, and the azimuthal anisotropies for these observables. Predictions for the leading-particle suppression at nucleon-nucleon centre-of-mass energies of 62.4 and 5500 GeV are presented. The limits of the eikonal approximation in the BDMPS approach, when applied to finite-energy partons, are discussed.
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    B decays into light scalar particles and glueball (2005)
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    The European physical journal 39 (2005), S. 71-86 
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    Notes: Abstract. The recent observations of f 0(980) in charmless B decays motivate further studies of scalar particle and glueball production in these processes. Amplitudes for charmless two-body B decays involving the members of the scalar nonet are presented based on the symmetries of the dominant penguin contribution. Different scenarios for the lightest scalar nonet are investigated in view of the presently available data. We describe the evidence from B decays for f 0(1500) with a flavor octet like mixing and the hints towards the members of the $q\bar{q}$ nonet of lowest mass. There is further support for the hypothesis of a broad 0 + + glueball acting as coherent background especially in $B\to K\overline K K$ . The estimated B decay rates into gluonic mesons represent a sizable fraction of the theoretically derived decay rate for ${b\to sg}$ .
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    Coherent production of pairs of parabosons of order 2 (2005)
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    The European physical journal 39 (2005), S. 109-121 
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    Notes: Abstract. A parameter-free statistical model is used to study multiplicity signatures for coherent production of charged pairs of parabosons of order p = 2 in comparison with those arising in the case of ordinary bosons, p = 1. Two non-negative real parameters arise because “ab” and “ba” are fundamentally distinct pair operators of charge “ + 1”, A-quanta and charge “-1”, B-quanta parabosons. In 3D plots of ${P_{m}}(q)\equiv$ “the probability of m paraboson charged pairs + q positive parabosons” versus $\langle n\rangle $ and $\langle n^2\rangle $ , the p = 1 curve is found to lie on the relatively narrow 2D p = 2 surface.
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    On the boundary conditions as Dirac constraints (2005)
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    The European physical journal 39 (2005), S. 123-127 
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    Notes: Abstract. In this paper, the canonical quantization of singular Lagrangian defined in a finite volume is discussed by studying a 1 + 1 dimensional free Schrödinger field. We take the boundary conditions (BCs) as Dirac constraints, and show that those BCs as well as the intrinsic constraints (which are introduced by the singularities of Lagrangian) form the second class constraints. The quantization is performed canonically.
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    Concerning the Landau pole in 3-3-1 models (2005)
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    The European physical journal 39 (2005), S. 101-107 
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    Notes: Abstract. Some 3-3-1 models predict the existence of a non-perturbative regime at the TeV scale. We study in these models and their supersymmetric extensions, the energy at which the non-perturbative limit and a Landau-like pole arise. An order of magnitude for the mass of the extra neutral vector boson, $Z^\prime$ , present in these models is also obtained.
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    Quark-meson SU(3) model in a Tamm-Dancoff inspired approximation (2005)
    Springer
    The European physical journal 38 (2005), S. 483-494 
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    Notes: Abstract. The non-linear chiral quark-meson U(3) x U(3) model is solved using the Tamm-Dancoff inspired approximation which is described in an earlier paper [Phys. Rev. D 58, 034003 (1998)]. The resulting system of 15 coupled non-linear differential equations self-consistently determines all quark-meson coupling constants. Also the obtained solutions for quark and meson fields are stable and physically acceptable. As the zeroth approximation of a more refined structure they were used to calculate SU(3) baryon octet magnetic moments and axial coupling constants with baryon state vectors containing valence quarks only, at this primordial level. The results are very promising, so possibilities to pursuit more sophistication and improved physical input is indicated.
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    Diffractive $\gamma \gamma$ production at hadron colliders (2005)
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    The European physical journal 38 (2005), S. 475-482 
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    Notes: Abstract. We compute the cross section for exclusive double-diffractive $\gamma \gamma$ production at the Tevatron, $p{\bar{p}} \to p + \gamma \gamma + {\bar{p}}$ , and the LHC. We evaluate both the gg and $q\bar{q}\;\; t$ -channel exchange contributions to the process. The observation of exclusive $\gamma \gamma$ production at the Tevatron will provide a check on the model predictions and offer an opportunity to confirm the expectations for exclusive double-diffractive Higgs production at the LHC.
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    Zero-curvature formalism of supersymmetric principal chiral model (2005)
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    The European physical journal 38 (2005), S. 521-526 
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    Notes: Abstract. We investigate the one-parameter family of transformations on superfields of the super principal chiral model and obtain different zero-curvature representations of the model. The parametric transformation is related to the super Riccati equations and an infinite set of local and non-local conservation laws is derived. A Lax representation of the model is presented which gives rise to a superspace monodromy operator.
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    Measurement of triple gauge boson couplings at an $e\gamma$ -collider (2005)
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    The European physical journal 38 (2005), S. 427-436 
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    Notes: Abstract. If no light Higgs boson exists, the interaction among the gauge bosons becomes strong at high energies ( $\sim 1 {\rm TeV}$ ). The effects of strong electroweak symmetry breaking (SEWSB) could manifest themselves indirectly as anomalous couplings before they give rise to new physical states like resonances. Here a study of the measurement of trilinear gauge couplings is presented looking at the hadronic decay channel of the W boson at an $e\gamma$ -collider. A sensitivity in the range of 10-3 to 10-4 can be reached depending on the coupling under consideration.
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    Casimir effect for gauge fields in spaces with negative constant curvature (2005)
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    The European physical journal 39 (2005), S. 249-252 
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    Notes: Abstract. We consider gauge theories based on abelian p-forms on real compact hyperbolic spaces. Using the zeta-function regularization method and the trace tensor kernel formula, we determine explicitly an expression for the vacuum energy (Casimir energy) corresponding to skew-symmetric tensor fields. It is shown that the topological component of the Casimir energy for co-exact forms on even-dimensional spaces, associated with the trivial character, is always negative. We infer on the possible cosmological consequences of this result.
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    Non-Abelian color dielectric - towards the effective model of the low energy QCD (2005)
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    The European physical journal 39 (2005), S. 185-193 
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    Notes: Abstract. Lattice motivated triplet color scalar field theory is analyzed. We consider non-minimal as well as covariant derivative coupling with SU(2) gauge fields. Field configurations generated by external electric sources are presented. Moreover non-Abelian magnetic monopoles are found. Dependence on the spatial coordinates in the obtained solutions is identical as in the usual Abelian case. We show also that after a decomposition of the fields a modified Faddeev-Niemi action can be obtained. It contains explicit O(3) symmetry breaking term parameterized by the condensate of an isoscalar field. Due to that Goldstone bosons observed in the original Faddeev-Niemi model are removed.
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    Comments on spin operators and spin-polarization states of 2 + 1 fermions (2005)
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    The European physical journal 39 (2005), S. 245-248 
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    Notes: Abstract. In this brief article we discuss spin-polarization operators and spin-polarization states of 2 + 1 massive Dirac fermions and find a convenient representation by the help of 4-spinors for their description. We stress that in particular the use of such a representation allows us to introduce the conserved covariant spin operator in the 2 + 1 field theory. Another advantage of this representation is related to the pseudoclassical limit of the theory. Indeed, quantization of the pseudoclassical model of a spinning particle in 2 + 1 dimensions leads to the 4-spinor representation as the adequate realization of the operator algebra, where the corresponding operator of a first-class constraint, which cannot be gauged out by imposing the gauge condition, is just the covariant operator previously introduced in the quantum theory.
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    Hidden local symmetry and chiral effective theory for vector and axial-vector mesons (2005)
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    The European physical journal 39 (2005), S. 201-208 
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    Notes: Abstract. In this paper, we present the full Lagrangian of mesons (pseudoscalars, vectors and axial-vectors) to O(p 4) by using the explicit global chiral symmetry and hidden local symmetry in the chiral limit. In this approach, we see that there are many other terms besides the usual eleven terms given in the literature from a hidden local symmetry approach. In particular, there are some terms in our full results which are important for understanding the vector meson dominance and $\pi$ - $\pi$ scattering and providing consistent predictions on the decay rates of $a_1\rightarrow\gamma\pi$ and $a_1\rightarrow\rho\pi$ as well as for constructing a consistent effective chiral Lagrangian with chiral perturbation theory. It is likely that the structures of the effective chiral Lagrangian for O(p 4) given in the literature by using hidden local symmetry are incomplete and consequently the resulting couplings are not reliable. We examine the issue that the more general effective chiral Lagrangian given in the present paper can provide more consistent predictions for the low energy phenomenology of the $\rho$ -a 1 system and result in more consistent descriptions on the low energy behavior of light flavor mesons.
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    Inelastic $J/\psi$ and $\Upsilon$ hadroproduction (2005)
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    The European physical journal 39 (2005), S. 163-171 
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    Notes: Abstract. We consider the prompt hadroproduction of $J/\psi, \psi'$ and the $\Upsilon (1S,2S,3S)$ states caused by the fusion of a symmetric colour-octet state, (gg)8s , and an additional gluon. The cross sections are calculated in leading-order perturbative QCD. We find a considerable enhancement in comparison with previous perturbative QCD predictions. Indeed, the resulting cross sections are found to be consistent with the values measured at the Tevatron and RHIC, without the need to invoke non-perturbative ‘colour-octet’ type of contributions.
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    Exclusive decuplet-baryon pair production in two-photon collisions (2005)
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    The European physical journal 39 (2005), S. 173-178 
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    Notes: Abstract. This work extends our previous studies of two-photon annihilation into baryon-antibaryon pairs from spin-1/2 octet to spin-3/2 decuplet baryons. Our approach is based on perturbative QCD and treats baryons as quark-diquark systems. Using the same model parameters as in our previous work, supplemented by QCD sum-rule results for decuplet baryon wave functions, we are able to give absolute predictions for decuplet baryon cross sections without introducing new parameters. We find that the $\Delta^{ + + }$ cross section is of the same order of magnitude as the proton cross section, well within experimental bounds.
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    Energy dependence of gap survival probability and antishadowing (2005)
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    The European physical journal 39 (2005), S. 435-438 
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    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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    Non-perturbative pion matrix element of a twist-2 operator from the lattice (2005)
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    The European physical journal 40 (2005), S. 69-80 
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    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.
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    Radiative K e3 decays revisited (2005)
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    The European physical journal 40 (2005), S. 205-227 
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    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.
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    Extension of the Buchalla-Safir bound (2005)
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    The European physical journal 40 (2005), S. 187-191 
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    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 $B \to \pi^ + \pi^-$ .
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    The Lorentz and CPT violating effects on the $Z\rightarrow l^ + l^-$ decay (2005)
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    The European physical journal 40 (2005), S. 269-273 
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    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.
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    Size of isospin breaking in charged $K_{\ell 4}$ decay (2005)
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    The European physical journal 40 (2005), S. 367-382 
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    Notes: Abstract. We evaluate the size of isospin breaking corrections to form factors f and g of the $K_{\ell 4}$ decay process $K^ + \rightarrow\pi^ + \pi^-\ell^ + \nu_{\ell}$ which is actually measured by the extended NA48 setup at CERN. We found that, keeping apart the effect of Coulomb interaction, isospin breaking does not affect the moduli. This is due to the cancellation between corrections of electromagnetic origin and those generated by the difference between up and down quark masses. On the other hand, electromagnetism affects considerably the phases if the infrared divergence is dropped out using a minimal subtraction scheme. Consequently, the greatest care must be taken in the extraction of $\pi\pi$ phase shifts from experiment.
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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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    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)
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    The European physical journal 40 (2005), S. 137-144 
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    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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    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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    Heavy quark vacuum polarization: first two moments of the ${\mathcal{O}}(\alpha_s^3 n_f^2)$ contribution (2005)
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    The European physical journal 40 (2005), S. 361-366 
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    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.
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    Isospin breaking in $K \to 3 \pi$ decays III : Bremsstrahlung and fit to experiment (2005)
    Springer
    The European physical journal 40 (2005), S. 383-394 
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    Notes: Abstract. We complete here our work on isospin violation in the $K \to 3 \pi$ system. We first calculate $K\to2\pi$ to the same order as we did $K \to 3 \pi$ in papers I and II of this series. This adds the effects of order G 27 p 2 (m u -m d ) and G 27 p 2 e 2 to earlier work. We calculate also the lowest order bremsstrahlung contributions, $K\to2\pi\gamma,3\pi\gamma$ . With these and our earlier results we perform a full fit to all available CP-conserving data in the $K\to2\pi,3\pi$ system including isospin violation effects. We perform these fits under various input assumptions as well as test the factorization and the vector dominance model for the weak NLO low energy constants.
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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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    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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    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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    Study of spin and decay-plane correlations of W bosons in the e + e $^-\rightarrow$ W + W- process at LEP (2005)
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    The European physical journal 40 (2005), S. 333-341 
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    Notes: Abstract. Data collected at LEP at centre-of-mass energies $\sqrt{s} = 189-209$ GeV are used to study correlations of the spin of W bosons using $\mathrm{e}^ + \mathrm{e}^-\to \mathrm{W}^ + \mathrm{W}^-\to {\ensuremath{\ell\nu\mathrm{q\bar{q}}}}$ events. Spin correlations are favoured by data, and found to agree with the Standard Model predictions. In addition, correlations between the W-boson decay planes are studied in $\mathrm{e}^ + \mathrm{e}^-{}\to{}\mathrm{W}^ + \mathrm{W}^- \to{}{\ensuremath{\ell\nu\mathrm{q\bar{q}}}}$ and $\mathrm{e}^ + \mathrm{e}^-{}\to{}\mathrm{W}^ + \mathrm{W}^-{}\to{}{\ensuremath{\text{q}\bar{\text{q}}\text{q}\bar{\text{q}}}}{}$ events. Decay-plane correlations are measured to be consistent with the Standard Model predictions.
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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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    ISSN: 1434-6052
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    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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    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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    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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    Realistic neutrino masses from multi-brane extensions of the Randall-Sundrum model? (2005)
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    The European physical journal 40 (2005), S. 539-554 
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    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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    Confinement from new global defect structures (2005)
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    The European physical journal 40 (2005), S. 531-537 
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    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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    Dispersion of incoherent spectral features in systems with strong electron-phonon coupling (2005)
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    The European physical journal 43 (2005), S. 11-18 
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    ISSN: 1434-6036
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    Topics: Physics
    Notes: Abstract. We study (inverse) photoemission from systems with strong coupling of doped carriers to phonons. Using an adiabatic approximation, we develop a method for calculating spectra. This method is particularly simple for systems where the electron-phonon coupling can be neglected in the initial state, e.g., the undoped t-J model. The theory then naturally explains why the electron-phonon coupling just leads to a broadening of spectra calculated without electron-phonon coupling, without changing the dispersion. This is in agreement with recent angle-resolved photoemission spectroscopy (ARPES) on undoped cuprates, and it supports the interpretation in terms of strong electron-phonon interaction. The theory also shows that for systems with strong electron-phonon coupling in the initial state, the result cannot in general be related to the spectrum obtained without electron-phonon coupling.
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    Electronic structure of the Sr0.4Ca13.6Cu24O41 incommensurate compound (2005)
    Springer
    The European physical journal 43 (2005), S. 29-37 
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    Topics: Physics
    Notes: Abstract. We extracted, from strongly-correlated ab-initio calculations, a complete model for the chain subsystem of the Sr0.4Ca13.6Cu24O41 incommensurate compound. A second neighbor t-J+V model has been determined as a function of the fourth crystallographic parameter τ, for both low and room temperature crystallographic structures. The analysis of the obtained model shows the crucial importance of the structural modulations on the electronic structure through the on-site energies and the magnetic interactions. The structural distortions are characterized by their long range effect on the cited parameters that hinder the reliability of analyses such as BVS. One of the most striking results is the existence of antiferromagnetic nearest-neighbor interactions for metal-ligand-metal angles of 90○. A detailed analysis of the electron localization and spin arrangement is presented as a function of the chain to ladder hole transfer and of the temperature. The obtained spin arrangement is in agreement with antiferromagnetic correlations in the chain direction at low temperature.
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    Bulk mediated surface diffusion: non Markovian desorption with finite first moment (2005)
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    The European physical journal 43 (2005), S. 65-71 
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    Notes: Abstract. Here we address a fundamental issue in surface physics: the dynamics of adsorbed molecules. We study this problem when the particle’s desorption is characterized by a non Markovian process, while the particle’s adsorption and its motion in the bulk are governed by a Markovian dynamics. We study the diffusion of particles in a semi-infinite cubic lattice, and focus on the effective diffusion process at the interface z = 1. We calculate analytically the conditional probability to find the particle on the z=1 plane as well as the surface dispersion as functions of time. The comparison of these results with Monte Carlo simulations show an excellent agreement.
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    Dielectric resonances of ordered passive arrays (2005)
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    The European physical journal 43 (2005), S. 81-92 
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    Topics: Physics
    Notes: Abstract. The electrical and optical properties of ordered passive arrays, constituted of inductive and capacitive components, are usually deduced from Kirchhoff’s rules. Under the assumption of periodic boundary conditions, comparable results may be obtained via an approach employing transfer matrices. In particular, resonances in the dielectric spectrum are demonstrated to occur if all eigenvalues of the transfer matrix of the entire array are unity. The latter condition, which is shown to be equivalent to the habitual definition of a resonance in impedance for an array between electrodes, allows for a convenient and accurate determination of the resonance frequencies, and may thus be used as a tool for the design of materials with a specific dielectric response. For the opposite case of linear arrays in a large network, where periodic boundary condition do not apply, several asymptotic properties are derived. Throughout the article, the derived analytic results are compared to numerical models, based on either Exact Numerical Renormalisation or the spectral method.
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    On the properties of cycles of simple Boolean networks (2005)
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    The European physical journal 43 (2005), S. 115-124 
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    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.
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    Mean field theory and geodesics in general relativity (2005)
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    The European physical journal 43 (2005), S. 143-154 
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    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.
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    Strain-induced properties of epitaxial VOx thin films (2005)
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    The European physical journal 43 (2005), S. 195-200 
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    Topics: Physics
    Notes: Abstract. We have grown VOx thin films on different substrates in order to investigate the influence of epitaxial strain on the transport properties. We found that the electric conductivity is much larger for films grown under compressive strain on SrTiO3 substrates, as compared to bulk material and VOx films grown under tensile strain on MgO substrates. A clear crossover from metallic to semiconducting behavior is observed when increasing the oxygen content x. Apparently, the application of strain induces a Mott-Hubbard insulator-to-metal transition in VOx〈1. The VOx/SrTiO3 films show an unexpected large positive magnetoresistance effect at low temperatures, which is not found in the VOx films grown under tensile strain on MgO or on a substrate with a similar lattice parameter.
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    Theory of neutron scattering for gapless neutral spin-1 collective mode in graphite (2005)
    Springer
    The European physical journal 43 (2005), S. 175-185 
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    ISSN: 1434-6036
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    Topics: Physics
    Notes: Abstract. Using tight binding band picture for 2D graphite, and the Hubbard interaction, recently we obtained a gapless, neutral spin-1 collective mode branch in graphite [Phys. Rev. Lett. 89, 016402]. In this paper we present a detailed RPA analysis of the Neutron Scattering cross section for this collective mode. Near K-point and very close to Γ-point, the intensity of neutron scattering peaks vanishes as q3. This is shown using a simple Dirac cone model for the graphite band structure, which captures the small-q behavior of the system. As we move away from the Γ- and K-points in the Brillouin zone of the collective mode momenta, we can identify our collective mode quanta with spin triplet excitons with the spatial extent of the order of a few to a couple of lattice parameter a, with more or less anisotropic character, which differs from point to point. We also demonstrate that the inclusion of the long range tail of the Coulomb interaction in real graphite, does not affect our spin-1 collective mode qualitatively. This collective mode could be probed at different energy scales by thermal, hot and epithermal neutron scattering experiments. However, the smallness of the calculated scattering intensity, arising from a reduced form factor of carbon 2pz orbital makes the detection challenging.
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    Magnetic AC susceptibility of stoichiometric and low zinc doped magnetite single crystals (2005)
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    The European physical journal 43 (2005), S. 201-212 
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    Notes: Abstract. Systematic studies of AC susceptibility in a stoichiometric magnetite single crystal, in a series of low zinc doped magnetite (xZn 〈 0.04) and in nonstoichiometric magnetite samples (both single crystals and pellets) in the temperature range 4–300 K are presented. Measurements were performed in several AC fields ( $H_{AC}=0.2{-}20\ $ Oe) and at different frequencies (15–6000 Hz). It is suggested that the signal is primarily due to magnetic domain wall movement, strongly influenced by structural domains (twins). Two sets of anomalies were found: the first is associated with the Verwey transition and the second involves two different effects, one at 28 K, observed only in stoichiometric magnetite, and the other at 50 K. While the temperature position of the first anomaly (28 K) does not depend on frequency, the effect at 50 K is associated with an activation process, shifting to higher temperatures with increasing frequency. This last effect may be linked to the low temperature magnetoelectric effects terminating approximately at those temperatures. Qualitatively similar results have been observed by the Magnetic After Effect technique presented in the literature, that is associated with relaxation times that are 104 higher than those characteristic of our technique.
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    HSSH-model of Hole transfer in DNA (2005)
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    The European physical journal 43 (2005), S. 279-281 
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    Topics: Physics
    Notes: Abstract. A method based on a selfconsistent solution of a quantum-mechanical system with temperature fluctuations described by Langevin equations is developed to calculate the charge carrier mobility in DNA. To model the charge transfer in DNA, a combined Holstein – SSH Hamiltonian is considered. As an example the hole mobility is calculated at room temperature for synthetic poly (G)/poly (C) duplex with regard to main structural fluctuations.
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    Ripple formation over a sand bed submitted to a laminar shear flow (2005)
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    The European physical journal 43 (2005), S. 283-294 
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    Topics: Physics
    Notes: Abstract. We investigate the process of ripple formation in a viscous fluid when a sand bed is submitted to a laminar shear flow. We propose a new description for the sand transport which takes into account the fact that the transport rate does not adapt instantaneously to a change of the fluid velocity due to grain inertia. It introduces a new length, called here after equilibrium length leq, corresponding to the distance needed for a immobile grain to equilibrate its velocity with that of the fluid. The transport rate is therefore found to depend not only on the fluid shear stress and bed slope (as usually assumed) but also on grain inertia. Within the framework of this model we analyzed the mechanisms of the sand bed instability. It is found that the instability results from the competition between the destabilizing effect of fluid inertia and the stabilizing ones of grain inertia and bed slope. We derive analytical scaling laws for the most amplified wavelength, its growth rate and phase velocity. We found in particular that at small particle Reynolds number Rep, the most amplified wavelength scales as the viscous length lν defined as $\sqrt{\nu/\gamma}$ (where γ is the shear rate and ν the fluid viscosity) and at large Rep it scales as the equilibrium length leq. Our results are compared with available experimental data.
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    Diagram technique for finding of vertex functions in the Landau theory of heteropolymer liquids (2005)
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    The European physical journal 43 (2005), S. 251-269 
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    Notes: Abstract. The problem on finding the coefficients of the Landau free energy expansion into the power series of parameter of order has been considered for solutions and melts of linear heteropolymers whose molecules comprise several types monomeric units arranged stochastically. The presence of such a quenched structural disorder places this problem outside the framework of the traditional statistical physics inviting for its solution special approaches. One of them, based on the replica concept and actively engaged in theoretical physics of disordered systems, has been invoked in this paper to derive expressions for the vertex functions in the Landau theory of heteropolymer liquids. An algorithm has been formulated which permits one resorting to the simple diagram technique to write down expressions for these functions of any order in terms of the statistical characteristics of chemical quenched structure of polymer molecules. Explicit expressions for the contributions to the Landau free energy up to the fourth degree of order parameters for polymer systems with an arbitrary structural disorder have been presented to illustrate this general algorithm. Its potentialities have been also exemplified for the melt of random m-component copolymer where exact analytical formulas for these contributions up to n=6 at an arbitrary m have been derived for the first time.
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    Uncompensated antiferromagnetic structure of Ho2Ni2Pb (2005)
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    The European physical journal 43 (2005), S. 163-174 
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    Topics: Physics
    Notes: Abstract. We have studied the magnetic structure of the orthorhombic compound Ho2Ni2Pb by means of neutron diffraction in zero field and in magnetic fields up to 4.5 T. Both powder and single-crystalline samples were used. Previous bulk measurements suggest two distinct magnetic phase transitions: one at TN = 7.0 K and the other at 4.8 K. Our neutron diffraction measurements, which were made in the range 1.5-20 K, showed that Ho2Ni2Pb has a collinear magnetic structure with unequal number of up and down Ho moments that are aligned parallel and antiparallel to the c axis. At the lowest temperatures the Ho moments are equal in size, each 8.3 μB in agreement with magnetization data. The magnetic structure can be described as having a 5a ×b ×c magnetic unit cell. Below Ts = 3.0 K the structure is squared up. A smooth development of all the magnetic moment magnitudes indicates that the magnetic structure remains in principle the same over the whole temperature range, the “phase transition” around 4.8 K can be identified as an inflection point in the temperature dependence of one of the Ho moments. With increasing temperature there is a clear development towards a simple transverse sine-wave modulated magnetic structure that is established just below TN.
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    Moment instabilities in multidimensional systems with noise (2005)
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    The European physical journal 43 (2005), S. 221-242 
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    Notes: Abstract. We present a systematic study of moment evolution in multidimensional stochastic difference systems, focusing on characterizing systems whose low-order moments diverge in the neighborhood of a stable fixed point. We consider systems with a simple, dominant eigenvalue and stationary, white noise. When the noise is small, we obtain general expressions for the approximate asymptotic distribution and moment Lyapunov exponents. In the case of larger noise, the second moment is calculated using a different approach, which gives an exact result for some types of noise. We analyze the dependence of the moments on the system’s dimension, relevant system properties, the form of the noise, and the magnitude of the noise. We determine a critical value for noise strength, as a function of the unperturbed system’s convergence rate, above which the second moment diverges and large fluctuations are likely. Analytical results are validated by numerical simulations. Finally, we present a short discussion of the extension of our results to the continuous time limit.
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    Frequency clustering of coupled phase oscillators on small-world networks (2005)
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    The European physical journal 43 (2005), S. 243-250 
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    Notes: Abstract. We analyze the phenomenon of frequency clustering in a system of coupled phase oscillators. The oscillators, which in the absence of coupling have uniformly distributed natural frequencies, are coupled through a small-world network, built according to the Watts-Strogatz model. We study the time evolution and determine variations in the transient times depending on the disorder of the network and on the coupling strength. We investigate the effects of fluctuations in the average frequencies, and discuss the definition of the threshold for synchronization. We characterize the structure of clusters and the distribution of cluster sizes in the synchronization transition, and define suitable order parameters to describe the aggregation of the oscillators as the network disorder and the coupling strength change. The non-monotonic behavior observed in some order parameters is related to fluctuations in the mean frequencies.
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    Interaction effects on persistent current of ballistic cylindrical nanostructures (2005)
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    The European physical journal 43 (2005), S. 405-419 
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    Notes: Abstract. We investigate clean cylindrical nanostructures with an applied longitudinal static magnetic field. The ground state of these systems becomes degenerate for particular values of the field due to Aharonov-Bohm effect. The Coulomb interaction introduces couplings between the electronic configurations. Consequently, depending on particular selection rules, the ground state may become, in the interacting case, a many body state at the degeneracy points: a gap is then opened. To study this problem, we propose a variational multireference wave function which goes beyond the Hartree-Fock approximation. Using this ansatz, in addition to the replacements of some crossings by avoided crossings, two other important effects of the electron-electron interaction are pointed out: (i) the long-range part of the Coulomb potential tends to shift the position in magnetic field of the crossing or avoided crossing points and, (ii) at the points of degeneracy or near degeneracy, the interaction can drive the system from a singlet to a triplet state inducing new real crossing points in the ground state energy curve as function of the field. In any case, the crossing points that are due to either orbital or spin effects, should manifest themselves in various experiments as sudden changes in the response of the system (magnetoconductance, magnetopolarisability, ...) when the magnetic field is tuned.
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    Polaron properties in ternary group-III nitride mixed crystals (2005)
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    The European physical journal 43 (2005), S. 339-345 
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    Notes: Abstract. Polaron properties are studied in bulk wurtzite nitride ternary mixed crystals AxB1-xN (A, B = Al, Ga, In) with the use of a dielectric continuum Fröhlich-like electron-phonon interaction Hamiltonian. The polaronic self-trapping energy and effective mass are analytically derived by taking the mixing properties of the LO and TO polarizations due to the anisotropy effect into account in the mono-phonon approximation. The numerical computation has been performed for the wurtzite ternary mixed crystal materials InxGa1-xN, AlxGa1-xN, and AlxIn1-xN as functions of the composition x. The results show that the polaronic self-trapping energies in the wurtzite structures are bigger than that in zinc-blende structures for the materials calculated. It is also found that the structure anisotropy increases the electron-phonon interaction in wurtizte nitride semiconductors. The results indicate that the LO-like phonon influence on the polaronic self-trapping energy and effective mass is dominant, and the anisotropy effect is obvious.
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    Dimer site-bond percolation on a square lattice (2005)
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    The European physical journal 43 (2005), S. 363-368 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. A generalization of the pure site and pure bond percolation problems in which pairs of nearest neighbor sites (site dimers) and linear pairs of nearest neighbor bonds (bond dimers) are independently occupied at random on a square lattice is studied. We called this model as dimer site-bond percolation. Motivated by considerations of cluster connectivity, we have used two distinct schemes (denoted as $S\cap B$ and $S\cup B$ ) for dimer site-bond percolation. In $S \cap B$ ( $S \cup B$ ), two points are said to be connected if a sequence of occupied sites and (or) bonds joins them. By using finite-size scaling theory, data from $S \cap B$ and $S \cup B$ are analyzed in order to determine i) the phase boundary between the percolating and non-percolating regions and ii) the numerical values of the critical exponents of the phase transition occurring in the system. The results obtained are discussed in comparison with the corresponding ones for classical monomer site-bond percolation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2005-00064-0
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  • 96
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    Ground-state correlations and finite temperature properties of the transverse Ising model (2005)
    Springer
    The European physical journal 43 (2005), S. 373-378 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We present a semi-analytic study of Ising spins on a simple square or cubic lattice coupled to a transverse magnetic field of variable strength. The formal analysis employs correlated basis functions (CBF) theory to investigate the properties of the corresponding N-body ground and excited states. For these states we discuss two different ansaetze of correlated trial wave functions and associated longitudinal and transverse excitation modes. The formalism is then generalized to describe the spin system at nonzero temperatures with the help of a suitable functional approximating the Helmholtz free energy. To test the quality of the functional in a first step we perform numerical calculations within the extended formalism but ignore spatial correlations. Numerical results are reported on the energies of the longitudinal and the transverse excitation modes at zero temperature, on critical data at finite temperatures, and on the optimized spontaneous magnetization as a function of temperature and external field strength.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2005-00066-x
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  • 97
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    Hydrogen desorption from ball milled MgH2 catalyzed with Fe (2005)
    Springer
    The European physical journal 43 (2005), S. 19-27 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2005-00023-9
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  • 98
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    Generic two-phase coexistence in nonequilibrium systems (2005)
    Springer
    The European physical journal 43 (2005), S. 73-79 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2005-00029-3
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  • 99
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    A model reaction diffusion system under spatial perturbation: theoretical and numerical investigation (2005)
    Springer
    The European physical journal 43 (2005), S. 109-114 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2005-00033-7
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  • 100
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    Decoherence and entanglement in coherent quantum tunneling of magnetization with dissipation (2005)
    Springer
    The European physical journal 43 (2005), S. 125-129 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2005-00035-5
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