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Nuclear Theory·nucl-th

Friday·March 18, 2016

7 papers—3 primary·4 cross-listed

All7Primary3Cross-lists4
  1. 01

    [Submitted on 17 Mar 2016]

    Calculation of phases of np- scattering for potentials Reid93 and Argonne v18 on the phase-function method

    V. I. Zhaba

    A known phase-functions method has been considered for calculation of a single-channel nucleon-nucleon scattering. The phase shifts of np- scattering turn out for modern realistic phenomenological nucleon-nucleon potentials Reid93 but Argonne v18. Influence of choice of numeral method is explored on the decision of phase equation. For the decision of phase equation as differential equation of 1th order numeral methods are used: Euler method and Runge-Kutta methods 2-, 3-, 4- and 5th orders of exactness. Numerically calculated phase shifts of np- scattering for potentials Reid93 and Argonne v18 are in good agreement with the results obtained with the other methods of original works. Based on the known phases of scattering one can obtain the full amplitude, the full cross-section and the partial scattering amplitude accordingly. The used Runge-Kutta methods can be applied for finding of phases shifts of the mixed channels of nucleon-nucleon scattering.

    Comments:
    9 pages, 2 tables
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1603.05382 [pdf]
    1 citation
  2. 02

    [Submitted on 17 Mar 2016]

    On the role of secondary pions in spallation targets

    Davide Mancusi🇫🇷 · Sergio Lo Meo🇮🇹 · Nicola Colonna🇮🇹 · Alain Boudard🇫🇷 · Miguel Antonio Cortés-Giraldo🇪🇸 · Joseph Cugnon🇧🇪 · Jean-Christophe David🇫🇷 · Sylvie Leray🇫🇷 · Jorge Lerendegui-Marco🇪🇸 · Cristian Massimi🇮🇹 · Vasilis Vlachoudis🇨🇭

    We use particle-transport simulations to show that secondary pions play a crucial role for the development of the hadronic cascade and therefore for the production of neutrons and photons from thick spallation targets. In particular, for the n_TOF lead spallation target, irradiated with 20 GeV/c protons, neutral pions are involved in the production of ~90% of the high-energy photons; charged pions participate in ~40% of the integral neutron yield. Nevertheless, photon and neutron yields are shown to be relatively insensitive to large changes of the average pion multiplicity in the individual spallation reactions. We characterize this robustness as a peculiar property of hadronic cascades in thick targets.

    Comments:
    17 pages, 14 figures. Submitted to Eur. Phys. J. A
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1603.05453 [pdf]
    EPJA(2017)·19 citations
  3. 03

    [Submitted on 17 Mar 2016]

    Single-particle spectral function of the hyperon in finite nuclei

    Isaac Vidana🇵🇹

    The spectral function of the hyperon in finite nuclei is calculated from the corresponding self-energy, which is constructed within a perturbative many-body approach using some of the hyperon-nucleon interactions of the Jülich and Nijmegen groups. Binding energies, wave functions and disoccupation numbers of different single-particle states are obtained for various hypernuclei from He to Pb. The agreement between the calculated binding energies and experimental data is qualitatively good. The small spin-orbit splitting of the and wave states is confirmed. The discrete and the continuum contributions of the single- spectral function are computed. Their appearance is qualitatively similar to that of the nucleons. The -factor, that measures the importance of correlations, is also calculated. Our results show that its value is relatively large, indicating that the hyperon is less correlated than nucleons. This is in agreement with the results obtained by other authors for the correlations of the in infinite nuclear matter. The disoccupation numbers are obtained by integrating the spectral function over the energy. Our results show that the discrete contribution to the disoccupation number decreases when increasing the momentum of the . This indicates that, in the production reactions of hypernuclei, the hyperon is mostly formed in a quasi-free state.

    Comments:
    27 pages, 9 figures, 4 tables. Corrected version accepted for publication in Nuclear Physics A
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1603.05635 [pdf]
    NPA(2017)·16 citations
  4. 04

    [Submitted on 16 Mar 2016] (cross-list from astro-ph.HE)

    Impact of the first-forbidden decay on the production of r-process peak

    Nobuya Nishimura🇬🇧 · Zsolt Podolyák🇬🇧 · Dong-Liang Fang🇨🇳 · Toshio Suzuki🇯🇵

    We investigated the effects of first-forbidden transitions in decays on the production of the r-process peak. The theoretical calculated -decay rates with -delayed neutron emission were examined using several astrophysical conditions. As the first-borbidden decay is dominant in neutron-rich nuclei, their inclusion shortens -decay lifetimes and shifts the abundance peak towards higher masses. Additionally, the inclusion of the -delayed neutron emission results in a wider abundance peak, and smoothens the mass distribution by removing the odd-even mass staggering. The effects are commonly seen in the results of all adopted astrophysical models. Nevertheless there are quantitative differences, indicating that remaining uncertainty in the determination of half-lives for nuclei is still significant in order to determine the production of the r-process peak.

    Comments:
    6 pages, 4 figures, 1 table, Phys. Lett. B, in press
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
    arXiv:
    1603.05257 [pdf]
    PLB(2016)·18 citations
  5. 05

    [Submitted on 17 Mar 2016] (cross-list from hep-th)

    Entropy Production, Hydrodynamics, and Resurgence in the Primordial Quark-Gluon Plasma from Holography

    Alex Buchel🇨🇦 · Michal P. Heller🇨🇦 · Jorge Noronha🇧🇷

    Microseconds after the Big Bang quarks and gluons formed a strongly-coupled non-conformal liquid driven out-of-equilibrium by the expansion of the Universe. We use holography to determine the non-equilibrium behavior of this liquid in a Friedmann-Lemaitre-Robertson-Walker Universe and develop an expansion for the corresponding entropy production in terms of the derivatives of the cosmological scale factor. We show that the resulting series has zero radius of convergence and we discuss its resurgent properties. Finally, we compute the resummed entropy production rate in de Sitter Universe at late times and show that the leading order approximation given by bulk viscosity effects can strongly overestimate/underestimate the rate depending on the microscopic parameters.

    Comments:
    7 pages, 1 figure; v2: various improvements in presentation, title changed by journal, matches the published version
    Subjects:
    High Energy Physics — Theory (hep-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1603.05344 [pdf]
    PRD(2016)·110 citations
  6. 06

    [Submitted on 15 Mar 2016] (cross-list from hep-ph)

    Systematics of oscillatory behavior in hadronic masses and widths

    Boris Tatischeff🇫🇷

    A systematic study of hadron masses and widths shows regular oscillations that can be fitted by a simple cosine function. This property can be observed when the difference between adjacent masses of each family is plotted versus the mean mass.

    Comments:
    5 pages, 8 figures, updated data and new figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1603.05505 [pdf]
    3 citations
  7. 07

    [Submitted on 17 Mar 2016] (cross-list from hep-ph)

    Renormalisation of the low-energy constants of chiral perturbation theory from loops with dynamical vector mesons

    Carla Terschlüsen🇸🇪 · Stefan Leupold (Uppsala U.)🇸🇪

    Starting from a relativistic Lagrangian for pseudoscalar Goldstone bosons and vector mesons in the antisymmetric tensor representation, a one-loop calculation is performed to pin down the divergent structures that appear for the effective low-energy action at chiral orders Q^2 and Q^4. The corresponding renormalisation-scale dependences of all low-energy constants up to chiral order Q^4 are determined. Calculations are carried out for both the pseudoscalar octet and the pseudoscalar nonet, the latter in the framework of chiral perturbation theory in the limit of a large number of colours.

    Comments:
    revised version, accepted for publication
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1603.05524 [pdf]
    PRD(2016)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE