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Nuclear Theory·nucl-th

Friday·March 13, 2015

10 papers—4 primary·6 cross-listed

All10Primary4Cross-lists6
  1. 01

    [Submitted on 12 Mar 2015]

    Quantal description of nucleon exchange in stochastic mean-field approach

    S. Ayik · O. Yilmaz · B. Yilmaz · A. S. Umar · A. Gokalp · G. Turan · D. Lacroix

    Nucleon exchange mechanism is investigated in central collisions of symmetric heavy-ions in the basis of the stochastic mean-field approach. Quantal diffusion coefficients for nucleon exchange are calculated by including non-Markovian effects and shell structure. Variances of fragment mass distributions are calculated in central collisions of Ca + Ca, Ca + Ca and Ni + Ni systems.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1503.03652 [pdf]
    PRC(2015)·22 citations
  2. 02

    [Submitted on 12 Mar 2015]

    Proton-H scattering calculation: Elastic and charge-exchange reactions up to 30 MeV

    A. Deltuva · A. C. Fonseca

    Proton-H elastic scattering and charge-exchange reaction HHe in the energy regime above four-nucleon breakup threshold are described in the momentum-space transition operator framework. Fully converged results are obtained using realistic two-nucleon potentials and two-proton Coulomb force as dynamic input. Differential cross section, proton analyzing power, outgoing neutron polarization, and proton-to-neutron polarization transfer coefficients are calculated between 6 and 30 MeV proton beam energy. Good agreement with the experimental data is found for the differential cross section both in elastic and charge-exchange reactions; the latter shows a complicated energy and angular dependence. The most sizable discrepancies between predictions and data are found for the proton analyzing power and outgoing neutron polarization in the charge-exchange reaction, while the respective proton-to-neutron polarization transfer coefficients are well described by the calculations.

    Comments:
    6 figures, to be published in Phys. Rev. C
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1503.03824 [pdf]
    PRC(2015)·14 citations
  3. 03

    [Submitted on 12 Mar 2015]

    Heavy quark bound states in a quark-gluon plasma: dissociation and recombination

    Jean-Paul Blaizot🇫🇷 · Davide De Boni🇬🇧 · Pietro Faccioli🇮🇹 · Giovanni Garberoglio🇮🇹

    We present a comprehensive approach to the dynamics of heavy quarks in a quark gluon plasma, including the possibility of bound state formation and dissociation. In this exploratory paper, we restrict ourselves to the case of an Abelian plasma, but the extension of the techniques used to the non Abelian case is straightforward. A chain of well defined approximations leads eventually to a generalized Langevin equation, where the force and the noise terms are determined from a correlation function of the equilibrium plasma, and depend explicitly on the configuration of the heavy quarks. We solve the Langevin equation for various initial conditions, various numbers of heavy quark-antiquark pairs, and various temperatures of the plasma. Results of simulations illustrate various expected phenomena: dissociation of bound states as a result of combined effects of screening of the potential and collisions with the plasma constituent, formation of bound pairs (recombination) that occurs when enough heavy quarks are present in the system.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1503.03857 [pdf]
    NPA(2016)·121 citations
  4. 04

    [Submitted on 3 Mar 2015]

    Collective flow in event-by-event partonic transport plus hydrodynamics hybrid approach

    Rajeev S. Bhalerao🇮🇳 · Amaresh Jaiswal🇩🇪 · Subrata Pal🇮🇳

    Complete evolution of the strongly interacting matter formed in ultrarelativistic heavy-ion collisions is studied within a coupled Boltzmann and relativistic viscous hydrodynamics approach. For the initial nonequilibrium evolution phase, we employ the AMPT model that explicitly includes event-by-event fluctuations in the number and positions of the participating nucleons as well as of the produced partons with subsequent parton transport. The ensuing near-equilibrium evolution of quark-gluon and hadronic matter is modeled within the (2+1)-dimensional viscous hydrodynamics. We probe the role of parton dynamics in generating and maintaining the spatial anisotropy in the preequilibrium phase. Substantial eccentricities epsilon_n are found to be generated in the event-by-event fluctuations in parton production from initial nucleon-nucleon collisions. For ultracentral heavy-ion collisions, the model is able to explain qualitatively the unexpected hierarchy of the harmonic flow coefficients v_n(p_T)(n=2-6) observed at LHC. We find that the results for v_n(p_T) are rather insensitive to the variation (within a range) of the time of switchover from AMPT parton transport to hydrodynamic evolution. The usual Grad and the recently proposed Chapman-Enskog-like (nonequilibrium) single-particle distribution functions are found to give very similar results for v_n(n=2-4). The model describes well both the RHIC and LHC data for v_n(p_T) at various centralities, with a constant shear viscosity to entropy density ratio of 0.08 and 0.12, respectively. The event-by-event distributions of v_{2,3} are in good agreement with the LHC data for midcentral collisions. The linear response relation v_n = k_n epsilon_n is found to be true for n=2,3, except at large values of epsilon_n, where a larger value of k_n is required, suggesting a small admixture of positive nonlinear response even for n=2,3.

    Comments:
    8 pages, 9 figures, v2: Same as the published version. Title changed
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1503.03862 [pdf]
    PRC(2015)·53 citations

Affiliations

first authorsco-authorsvia INSPIRE