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  • Articles  (6,045)
  • Springer  (6,045)
  • American Chemical Society (ACS)
  • 2020-2024  (9)
  • 2015-2019  (6,036)
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  • Articles  (6,045)
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  • Springer  (6,045)
  • American Chemical Society (ACS)
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  • 1
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    Measurement of jet production cross sections in deep-inelastic ep scattering at HERA (2017)
    Springer
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    Publication Date: 2017-04-01
    Description: A precision measurement of jet cross sections in neutral current deep-inelastic scattering for photon virtualities $$5.5
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    Topics: Physics
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  • 2
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    Determination of the strong coupling constant $${varvec{{alpha _mathrm{s} (m_mathrm{Z})}}}$$ in next-to-next-to-leading order QCD using H1 jet cross section measurements (2017)
    Springer
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    Publication Date: 2017-11-01
    Description: The strong coupling constant $$alpha _mathrm{s}$$ α s is determined from inclusive jet and dijet cross sections in neutral-current deep-inelastic ep scattering (DIS) measured at HERA by the H1 collaboration using next-to-next-to-leading order (NNLO) QCD predictions. The dependence of the NNLO predictions and of the resulting value of $$alpha _mathrm{s} (m_mathrm{Z})$$ α s ( m Z ) at the Z-boson mass $$m_Z$$ m Z are studied as a function of the choice of the renormalisation and factorisation scales. Using inclusive jet and dijet data together, the strong coupling constant is determined to be $$alpha _mathrm{s} (m_mathrm{Z}) =0.1157,(20)_mathrm{exp},(29)_mathrm{th}$$ α s ( m Z ) = 0.1157 ( 20 ) exp ( 29 ) th . Complementary, $$alpha _mathrm{s} (m_mathrm{Z})$$ α s ( m Z ) is determined together with parton distribution functions of the proton (PDFs) from jet and inclusive DIS data measured by the H1 experiment. The value $$alpha _mathrm{s} (m_mathrm{Z}) =0.1142,(28)_mathrm{tot}$$ α s ( m Z ) = 0.1142 ( 28 ) tot obtained is consistent with the determination from jet data alone. The impact of the jet data on the PDFs is studied. The running of the strong coupling is tested at different values of the renormalisation scale and the results are found to be in agreement with expectations.
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  • 3
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    Higgs inflation and general initial conditions (2015)
    Springer
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    Publication Date: 2015-08-04
    Description: A Higgs field of particle physics can play the role of the inflaton in the early universe if it is non-minimally coupled to gravity. The Higgs inflation scenario predicts a small tensor to scalar ratio: \(r\simeq 0.003\) . Although this value is consistent with the upper bound \(r〈0.12\) given by the BICEP2/ Keck Array and Planck data, it is not at their maximum likelihood point: \(r\simeq 0.05\) . Inflationary observables depend not only on the inflationary models, but they also depend on the initial conditions of inflation. Changing the initial state of inflation can improve the value of r . In this work, we study the Higgs inflation model under general initial conditions and show that there is a subset of these general initial conditions which leads to enhancement of r . Then we show that this region of parameter space is consistent with a non-Gaussianity bound.
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  • 4
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    Wormholes admitting conformal Killing vectors and supported by generalized Chaplygin gas (2015)
    Springer
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    Publication Date: 2015-08-04
    Description: When Morris and Thorne first proposed that traversable wormholes may be actual physical objects, they concentrated on the geometry by specifying the shape and redshift functions. This mathematical approach necessarily raises questions regarding the determination of the required stress-energy tensor. This paper discusses a natural way to obtain a complete wormhole solution by assuming that the wormhole (1) is supported by generalized Chaplygin gas and (2) admits conformal Killing vectors.
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  • 5
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    Analysis of the $$\Lambda _c(2625)$$ Λ c ( 2625 ) and $$\Xi _c( (2015)
    Springer
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    Publication Date: 2015-08-08
    Description: In this article, we study the charmed baryon states \(\Lambda _c(2625)\) and \(\Xi _c(2815)\) with the spin-parity \({3\over 2}^-\) by subtracting the contributions from the corresponding charmed baryon states with the spin-parity \({3\over 2}^+\) using the QCD sum rules, and suggest a formula \( \mu =\sqrt{M_{\Lambda _c/\Xi _c}^2-{\mathbb {M}}_c^2}\) with the effective mass \({\mathbb {M}}_c=1.8\,\mathrm {GeV}\) to determine the energy scales of the QCD spectral densities, and make reasonable predictions for the masses and pole residues. The numerical results indicate that the \(\Lambda _c(2625)\) and \(\Xi _c(2815)\) have at least two remarkable under-structures.
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  • 6
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    Radiative leptonic $$B_c\rightarrow \gamma \ell {\bar{\nu }}$$ B c → γ ℓ (2015)
    Springer
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    Publication Date: 2015-08-08
    Description: We study the radiative leptonic \(B_c\rightarrow \gamma \ell {\bar{\nu }}\) decays in nonrelativistic QCD effective field theory, and we explore the contribution from a fast-moving photon. As a result, interactions between the photon and the heavy quarks can be integrated out, resulting in the factorization formula for the decay amplitude. We calculate not only the relevant short-distance coefficients at leading order and next-to-leading order in \(\alpha _s\) , but also the nonrelativistic corrections at the order \(|\mathrm {v}|^2\) in our analysis. We find that the QCD corrections can significantly decrease the branching ratio, and this is of great importance in extracting the long-distance operator matrix elements of \(B_c\) . For phenomenological application, we present our results for the photon energy, lepton energy and lepton-neutrino invariant mass distribution.
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  • 7
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    Zero average values of cosmological perturbations as an indispensable condition for the theory and simulations (2015)
    Springer
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    Publication Date: 2015-08-23
    Description: We point out a weak side of the commonly used determination of scalar cosmological perturbations lying in the fact that their average values can be nonzero for some matter distributions. It is shown that introduction of the finite-range gravitational potential instead of the infinite-range one resolves this problem. The concrete illustrative density profile is investigated in detail in this connection.
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  • 8
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    Topological vortices in generalized Born–Infeld–Higgs electrodynamics (2015)
    Springer
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    Publication Date: 2015-08-23
    Description: A consistent BPS formalism to study the existence of topological axially symmetric vortices in generalized versions of the Born–Infeld–Higgs electrodynamics is implemented. Such a generalization modifies the field dynamics via the introduction of three nonnegative functions depending only in the Higgs field, namely, \(G(|\phi |)\) , \(w(|\phi |) \) , and \(V(|\phi |)\) . A set of first-order differential equations is attained when these functions satisfy a constraint related to the Ampère law. Such a constraint allows one to minimize the system’s energy in such way that it becomes proportional to the magnetic flux. Our results provides an enhancement of the role of topological vortex solutions in Born–Infeld–Higgs electrodynamics. Finally, we analyze a set of models entailing the recovery of a generalized version of Maxwell–Higgs electrodynamics in a certain limit of the theory.
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  • 9
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    Quantum relaxation of the Higgs mass (2015)
    Springer
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    Publication Date: 2015-08-25
    Description: I put forward a qualitatively new dynamical mechanism for solving the electroweak hierarchy problem that does not require new physics at the electroweak scale. I argue that the infrared fluctuations of the gravitational field may provide a partial screening of the Higgs mass, similar to the infrared screening of the electric charge in quantum electrodynamics.
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  • 10
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    X-ray spectropolarimetric measurements of the Kerr metric (2015)
    Springer
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    Publication Date: 2015-08-25
    Description: It is thought that the spacetime geometry around black hole candidates is described by the Kerr solution, but an observational confirmation is still missing. Today, the continuum-fitting method and the analysis of the iron K \(\alpha \) line cannot unambiguously test the Kerr paradigm because of the degeneracy among the parameters of the system, in the sense that it is impossible with current X-ray data to distinguish a Kerr black hole from a non-Kerr object with different values of the model parameters. In this paper, we study the possibility of testing the Kerr nature of black hole candidates with X-ray spectropolarimetric measurements. Within our simplified model that does not include the effect of returning radiation, we find that it is impossible to test the Kerr metric and the problem is still the strong correlation between the spin and possible deviations from the Kerr geometry. Moreover, the correlation is very similar to that of the other two techniques, which makes the combination of different measurements not very helpful. Nevertheless, our results cannot be taken as conclusive and, in order to arrive at a final answer, the effect of returning radiation should be properly taken into account.
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