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Nuclear Theory·nucl-th

Monday·February 9, 2015

9 papers—7 primary·2 cross-listed

All9Primary7Cross-lists2
  1. 01

    [Submitted on 5 Feb 2015]

    Direct photon production at RHIC and LHC energies

    O. Linnyk🇩🇪 · E. L. Bratkovskaya🇩🇪 · W. Cassing🇩🇪

    Direct photon spectra and elliptic flow v2 in heavy-ion collisions at RHIC and LHC energies are investigated within a relativistic transport approach incorporating both hadronic and partonic phases - the Parton-Hadron-String Dynamics (PHSD). The results suggest that a large v2 of the direct photons - as observed by the PHENIX Collaboration - signals a significant contribution of photons produced in interactions of secondary mesons and baryons in the late stages of the collision. In order to further differentiate the origin of the direct photon azimuthal asymmetry, we compare our predictions for the centrality dependence of the direct photon yield to the recent measurements by the PHENIX Collaboration and provide predictions for Pb+Pb collisions at LHC energies with respect to the direct photon spectra and v2(pT) for 0-40% centrality.

    Comments:
    11 pages, 6 figures, talk at the XXII International Baldin Seminar on High Energy Physics Problems, 15-20 September, 2014, JINR, Dubna, Russia
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1502.01724 [pdf]
    PoS(2015)·1 citation
  2. 02

    [Submitted on 5 Feb 2015]

    Long-range correlation studies at the SPS energies in MC model with string fusion

    Vladimir Kovalenko🇷🇺 · Vladimir Vechernin🇷🇺

    Studies of the ultrarelativistic collisions of hadrons and nuclei at different centrality and energy enable to explore the QCD phase diagram in a wide range of temperature and baryon density. Long-range correlation studies are considered as a tool, sensitive to the observation of phase transition and the critical point. In the present work, a Monte Carlo model of proton-proton, proton-nucleus, and nucleus-nucleus collisions is applied to heavy and light ion collisions at the cms energy range from a few up to several hundred GeV per nucleon. The model describes the nuclear collisions at the partonic level through interaction of color dipoles and takes into account the effects of string fusion, which can be considered as an alternative to relativistic hydrodynamics way of describing the collective phenomena in heavy-ion collisions. The implementing of both the string fusion and the finite rapidity length of strings allowed to consider the particle production at non-zero baryochemical potential. We calculated the long-range correlation functions and correlation coefficients between multiplicities and transverse momentum at several energies for different colliding systems and obtained predictions for the experiment.

    Comments:
    15 pages, 8 figures, proc. Baldin ISHEPP XXII
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1502.01758 [pdf]
    Pos(2015)·3 citations
  3. 03

    [Submitted on 6 Feb 2015]

    Calculation and evaluation of cross-sections for p+184W reactions up to 200MeV

    Jianping Sun · Zhengjun Zhang · Yinlu Han

    The cross-sections of proton-induced reactions on 184W at incident proton energy below 200MeV are calculated and analyzed including reaction cross-sections, elastic scattering angular distributions, energy spectra and double differential cross section. Nuclear theoretical models which integrate the optical model, distorted born wave approximation theory, the intra-nuclear cascade model, the exciton model, the Hauser-Feshbach theory and the evaporation model are used in the reactions. Theoretical results are compared with the existent experimental data.

    Comments:
    18 pages,13 figures,3 tables
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1502.01831 [pdf]
    CPC(2015)·0 citations
  4. 04

    [Submitted on 6 Feb 2015]

    Deuteron-deuteron scattering above four-nucleon breakup threshold

    A. Deltuva · A. C. Fonseca

    Deuteron-deuteron elastic scattering and transfer reactions in the energy regime above four-nucleon breakup threshold are described by solving exact four-particle equations for transition operators. Several realistic nuclear interaction models are used, including the one with effective many-nucleon forces generated by the explicit -isobar excitation; the Coulomb force between protons is taken into account as well. Differential cross sections, deuteron analyzing powers, outgoing nucleon polarization, and deuteron-to-neutron polarization transfer coefficients are calculated at 10 MeV deuteron energy. Overall good agreement with the experimental data is found. The importance of breakup channels is demonstrated.

    Comments:
    5 figures
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1502.01910 [pdf]
    PLB(2015)·23 citations
  5. 05

    [Submitted on 6 Feb 2015]

    Vector Meson Spectral Functions in a Coarse-Graining Approach

    Stephan Endres🇩🇪 · Hendrik van Hees🇩🇪 · Janus Weil🇩🇪 · Marcus Bleicher🇩🇪

    Dilepton production in heavy-ion collisions at top SPS energy is investigated within a coarse-graining approach that combines an underlying microscopic evolution of the nuclear reaction with the application of medium-modified spectral functions. Extracting local energy and baryon density for a grid of small space-time cells and going to each cell's rest frame enables to determine local temperature and chemical potential by application of an equation of state. This allows for the calculation of thermal dilepton emission. We apply and compare two different spectral functions for the : A hadronic many-body calculation and an approach that uses empirical scattering amplitudes. Quantitatively good agreement of the model calculations with the data from the NA60 collaboration is achieved for both spectral functions, but in detail the hadronic many-body approach leads to a better description, especially of the broadening around the pole mass of the and for the low-mass excess. We further show that the presence of a pion chemical potential significantly influences the dilepton yield.

    Comments:
    9 pages, 2 figures; Contribution for proceedings of the Resonance Workshop in Catania 2014
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1502.01948 [pdf]
    EPJ Web Conf.(2015)·3 citations
  6. 06

    [Submitted on 6 Feb 2015]

    Estimation of the shear viscosity at finite net-baryon density from A+A collision data at GeV

    Iu. A. Karpenko🇺🇦 · P. Huovinen🇩🇪 · H. Petersen🇩🇪 · M. Bleicher🇩🇪

    Hybrid approaches based on relativistic hydrodynamics and transport theory have been successfully applied for many years for the dynamical description of heavy ion collisions at ultrarelativistic energies. In this work a new viscous hybrid model employing the hadron transport approach UrQMD for the early and late non-equilibrium stages of the reaction, and 3+1 dimensional viscous hydrodynamics for the hot and dense quark-gluon plasma stage is introduced. This approach includes the equation of motion for finite baryon number, and employs an equation of state with finite net-baryon density to allow for calculations in a large range of beam energies. The parameter space of the model is explored, and constrained by comparison with the experimental data for bulk observables from SPS and the phase I beam energy scan at RHIC. The favored parameter values depend on energy, but allow to extract the effective value of the shear viscosity coefficient over entropy density ratio in the fluid phase for the whole energy region under investigation. The estimated value of increases with decreasing collision energy, which may indicate that of the quark-gluon plasma depends on baryochemical potential .

    Comments:
    minor changes in the text, results for constant eta*T/w added. Version accepted for publication in Phys. Rev. C
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1502.01978 [pdf]
    PRC(2015)·212 citations
  7. 07

    [Submitted on 6 Feb 2015]

    Single-Particle Spectrum of Pure Neutron Matter

    Khalaf Gad🇪🇬 · Hesham Mansour🇪🇬

    We have calculated the self-consistent auxiliary potential effects on the binding energy of neutron matter using the Brueckner Hartree Fock approach by adopting the Argonne V18 and CD-Bonn potentials. The binding energy with the four different choices for the self-consistent auxiliary potential is discussed. Also, the binding energy of neutron matter has been computed within the framework of the self-consistent Green s function approach. We also compare the binding energies obtained in this study with those obtained by various microscopic approaches.

    Comments:
    5 pages,4 figures in Journal of the Physical Society of Japan Volume 84, Issue 3 (March 15, 2015) Journal of the Physical Society of Japan Volume 84, Issue 2 (February 15, 2015). arXiv admin note: text overlap with arXiv:1310.1547 by other authors
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1502.01984 [pdf]
    J.Phys.Soc.Jap.(2015)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE