PaperPanorama
FAQ

Nuclear Theory·nucl-th

Tuesday·September 6, 2016

9 papers—5 primary·4 cross-listed

All9Primary5Cross-lists4
  1. 06

    [Submitted on 2 Sept 2016] (cross-list from hep-ph)

    Revisiting the equivalence of light-front and covariant QED in the light-cone gauge

    Luca Mantovani🇮🇹 · Barbara Pasquini🇮🇹 · Xiaonu Xiong🇮🇹 · Alessandro Bacchetta🇮🇹

    We discuss the equivalence between light-front time-ordered-perturbation theory and covariant quantum field theory in light-front quantization, in the case of quantum electrodynamics at one-loop level. In particular, we review the one-loop calculation of the vertex correction, fermion self-energy and vacuum polarization. We apply the procedure of integration by residue over the light-front energy in the loop to show how the perturbative expansion in covariant terms can be reduced to a sum of propagating and instantaneous diagrams of light-front time-ordered perturbation theory. The detailed proof of equivalence between the two formulations of the theory resolves the controversial question on which form should be used for the gauge-field propagator in the light-cone gauge in the covariant approach.

    Comments:
    18 pages, 5 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1609.00746 [pdf]
    PRD(2016)·14 citations
  2. 07

    [Submitted on 4 Sept 2016] (cross-list from hep-ph)

    First Monte Carlo analysis of fragmentation functions from single-inclusive annihilation

    N. Sato🇺🇸 · J.J. Ethier🇺🇸 · W. Melnitchouk🇺🇸 · M. Hirai🇯🇵 · S. Kumano🇯🇵 · A. Accardi🇺🇸

    We perform the first iterative Monte Carlo (IMC) analysis of fragmentation functions constrained by all available data from single-inclusive annihilation into pions and kaons. The IMC method eliminates potential bias in traditional analyses based on single fits introduced by fixing parameters not well contrained by the data and provides a statistically rigorous determination of uncertainties. Our analysis reveals specific features of fragmentation functions using the new IMC methodology and those obtained from previous analyses, especially for light quarks and for strange quark fragmentation to kaons.

    Comments:
    44 pages, 11 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
    arXiv:
    1609.00899 [pdf]
    PRD(2016)·92 citations
  3. 08

    [Submitted on 4 Sept 2016] (cross-list from nucl-ex)

    Gamma strength function and level density of Pb from forward-angle proton scattering at 295 MeV

    S. Bassauer · P. von Neumann-Cosel · A. Tamii

    Gamma strength functions (GSFs) and level densities (LDs) are essential ingredients of statistical nuclear reaction theory with many applications in astrophysics, reactor design, and waste transmutation. The aim of the present work is a test of systematic parametrizations of the GSF recommended by the RIPL-3 data base for the case of Pb. The upward GSF and LD in Pb are compared to gamma decay data from an Oslo-type experiment to examine the validity of the Brink-Axel (BA) hypothesis. The E1 and M1 parts of the total GSF are determined from high-resolution forward angle inelastic proton scattering data taken at 295 MeV at RCNP, Osaka, Japan. The total LD in Pb is derived from the LD extracted with a fluctuation analysis in the energy region of the isovector giant dipole resonance. The E1 GSF is compared to parametrizations recommended by the RIPL-3 data base showing systematic deficiencies of all models in the energy region around neutron threshold. The new data for the poorly known spinflip M1 resonance call for a substantial revision of the model suggested in RIPL-3. The total GSF derived from the present data is larger in the PDR energy region than the Oslo data but the strong fluctuations due to the low LD resulting from the double shell closure of Pb prevent a conclusion on a possible violation of the BA hypothesis. Using the parameters suggested by RIPL-3 for a description of the LD in Pb with the back-shifted Fermi gas model, remarkable agreement between the two experiments spanning a wide excitation energy range is obtained. Systematic parametrizations of the E1 and M1 GSF parts need to be reconsidered at low excitation energies. The good agreement of LD provides an independent confirmation of the approach underlying the decomposition of GSF and LDs in Oslo-type experiments.

    Comments:
    7 pages, 8 figures
    Subjects:
    Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1609.00937 [pdf]
    PRC(2016)·27 citations
  4. 09

    [Submitted on 5 Sept 2016] (cross-list from hep-ph)

    Structure of charmed baryons studied by pionic decays

    Hideko Nagahiro🇯🇵 · Shigehiro Yasui🇯🇵 · Atsushi Hosaka🇯🇵 · Makoto Oka🇯🇵 · Hiroyuki Noumi🇯🇵

    We investigate the decays of the charmed baryons aiming at the systematic understanding of hadron internal structures based on the quark model by paying attention to heavy quark symmetry. We evaluate the decay widths from the one pion emission for the known excited states, \Lambda_c^*(2595), \Lambda_c^*(2625), \Lambda_c^*(2765), \Lambda_c^*(2880) and \Lambda_c^*(2940), as well as for the ground states \Sigma_c(2455) and \Sigma_c^*(2520). The decay properties of the lower excited charmed baryons are well explained, and several important predictions for higher excited baryons are given. We find that the axial-vector type coupling of the pion to the light quarks is essential, which is expected from chiral symmetry, to reproduce the decay widths especially of the low lying \Lambda_c^* baryons. We emphasize the importance of the branching ratios of \Gamma(\Sigma_c^*\pi)/\Gamma(\Sigma_c\pi) for the study of the nature of higher excited \Lambda_c^* baryons.

    Comments:
    20 pages, 5 figures, 11 tables
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1609.01085 [pdf]
    PRD(2017)·91 citations

Affiliations

first authorsco-authorsvia INSPIRE