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Nuclear Theory·nucl-th

Tuesday·August 18, 2015

16 papers—7 primary·9 cross-listed

All16Primary7Cross-lists9
  1. 01

    Nuclear Level Density: Shell Model vs Mean Field

    Roman Sen'kov · Vladimir Zelevinsky

    The knowledge of the nuclear level density is necessary for understanding various reactions including those in the stellar environment. Usually the combinatorics of Fermi-gas plus pairing is used for finding the level density. Recently a practical algorithm avoiding diagonalization of huge matrices was developed for calculating the density of many-body nuclear energy levels with certain quantum numbers for a full shell-model Hamiltonian. The underlying physics is that of quantum chaos and intrinsic thermalization in a closed system of interacting particles. We briefly explain this algorithm and, when possible, demonstrate the agreement of the results with those derived from exact diagonalization. The resulting level density is much smoother than that coming from the conventional mean-field combinatorics. We study the role of various components of residual interactions in the process of thermalization, stressing the influence of incoherent collision-like processes. The shell-model results for the traditionally used parameters are also compared with standard phenomenological approaches.

    nucl-thPRC(2016)·46 citations
  2. 02

    New Measurements and Phase Shift Analysis of p16O Elastic Scattering at Astrophysical Energies

    Sergey Dubovichenko · Nasurlla Burtebaev · Albert Dzhazairov-Kakhramanov · Denis Zazulin · Zhambyl Kerimkulov · Maulen Nassurlla · Chingis Omarov · Alesya Tkachenko · Tatyana Shmygaleva · Stanislaw Kliczewski · Turlan Sadykov

    The results of new experimental measurements of p16O elastic scattering in the energy range of 0.6-1.0 MeV at angles of 40-160 deg. are given. Phase shift analysis of p16O elastic scattering was made using these and other experimental data on differential cross sections in excitation functions and angular distributions at energies of up to 2.5 MeV.

    nucl-thCPC(2017)·9 citations
  3. 03

    Event-by-event distribution of magnetic field energy over initial fluid energy density in = 200 GeV Au-Au collisions

    Victor Roy🇩🇪 · Shi Pu🇩🇪

    We estimate the event-by-event (e-by-e) distribution of the ratio () of the magnetic field energy to the fluid energy density in the transverse plane of Au-Au collisions at = 200 GeV. A Monte-Carlo (MC) Glauber model is used to calculate the in the transverse plane for impact parameter b=0, 12 fm at time 0.5 fm. The fluid energy density is obtained by using Gaussian smoothing with two different smoothing parameter =0.25 , 0.5 fm. For collisions is found to be 1 in the central region of the fireball and 1 at the periphery. For b=12 fm collisions 1. The e-by-e correlation between and the fluid energy density () is studied. We did not find strong correlation between and at the centre of the fireball, whereas they are mostly anti-correlated at the periphery of the fireball.

    nucl-thhep-phPRC(2015)·73 citations
  4. 04

    ND^(*) and NB^(*) interactions in a chiral quark model

    Dan Yang🇨🇳 · Jing Liu🇨🇳 · Dan Zhang🇨🇳

    ND and ND^* interactions become a hot topic after the observation of new charmed hadrons \Sigma_c(2800) and \Lambda_c(2940)^+. In this letter, we have preliminary investigated S-wave ND and ND^* interactions with possible quantum numbers in the chiral SU(3) quark model and the extended chiral SU(3) quark model by solving the resonating group method equation. The numerical results show that the interactions between N and D or N and D^* are both attractive, which are mainly from \sigma exchanges between light quarks. Further bound-state studies indicate the attractions are strong enough to form ND or ND^* molecules, except for (ND)_{J=3/2} and (ND^*)_{J=3/2} in the chiral SU(3) quark model. In consequence ND system with J=1/2 and ND^* system with J=3/2 in the extended SU(3) quark model could correspond to the observed \Sigma_c(2800) and \Lambda_c(2940)^+, respectively. Naturally, the same method can be applied to research NB and NB^* interactions, and similar conclusions obtained, i.e. NB and NB^* attractive forces may achieve bound states, except for (NB^*)_{J=3/2} in the chiral SU(3) quark model. Meanwhile, S partial wave phase shifts of ND^{(*)} and NB^{(*)} elastic scattering are illustrated, which are qualitatively consistent with results from bound state problem.

    nucl-thhep-ph5 citations
  5. 05

    Heavy flavor in relativistic heavy-ion collisions

    E. L. Bratkovskaya🇩🇪 · T. Song🇩🇪 · H. Berrehrah🇩🇪 · D. Cabrera🇩🇪 · J. M. Torres-Rincon🇫🇷 · L. Tolos🇩🇪 · W. Cassing🇩🇪

    We study charm production in ultra-relativistic heavy-ion collisions by using the Parton-Hadron-String Dynamics (PHSD) transport approach. The initial charm quarks are produced by the PYTHIA event generator tuned to fit the transverse momentum spectrum and rapidity distribution of charm quarks from Fixed-Order Next-to-Leading Logarithm (FONLL) calculations. The produced charm quarks scatter in the quark-gluon plasma (QGP) with the off-shell partons whose masses and widths are given by the Dynamical Quasi-Particle Model (DQPM), which reproduces the lattice QCD equation-of-state in thermal equilibrium. The relevant cross sections are calculated in a consistent way by employing the effective propagators and couplings from the DQPM. Close to the critical energy density of the phase transition, the charm quarks are hadronized into mesons through coalescence and/or fragmentation. The hadronized mesons then interact with the various hadrons in the hadronic phase with cross sections calculated in an effective lagrangian approach with heavy-quark spin symmetry. The nuclear modification factor and the elliptic flow of mesons from PHSD are compared with the experimental data from the STAR Collaboration for Au+Au collisions at =200 GeV and to the ALICE data for Pb+Pb collisions at =2.76 TeV. We find that in the PHSD the energy loss of mesons at high can be dominantly attributed to partonic scattering while the actual shape of versus reflects the heavy-quark hadronization scenario, i.e. coalescence versus fragmentation. Also the hadronic rescattering is important for the at low and enhances the -meson elliptic flow .

    nucl-thhep-phJ.Phys.Conf.Ser.(2016)·5 citations
  6. 06

    Interferometry for rotating sources

    S. Velle🇳🇴 · S. Mehrabi Pari🇳🇴 · L.P. Csernai🇳🇴

    The two particle interferometry method to determine the size of the emitting source after a heavy ion collision is extended. Following the extension of the method to spherical expansion dynamics, here we extend the method to rotating systems. It is shown that rotation of a cylindrically symmetric system leads to modifications, which can be perceived as spatial asymmetry by the "azimuthal HBT" method. We study an exact rotating and expanding solution of the fluid dynamical model of heavy ion reactions. We consider a source that is azimuthally symmetric in space around the axis of rotation, and discuss the features of the resulting two particle correlation function. This shows the azimuthal asymmetry arising from the rotation. We show that this asymmetry leads to results similar to those given by spatially asymmetric sources.

    nucl-thPLB(2016)·7 citations
  7. 07

    Superdeformed band in the nucleus Ar: A projected shell model analysis

    Ying-Chun Yang · Yan-Xin Liu · Yang Sun · Mike Guidry

    It has been debated whether the experimentally-identified superdeformed rotational band in Ar [E. Ideguchi, et al., Phys. Lett. B 686 (2010) 18] has an axially or triaxially deformed shape. Projected shell model calculations with angular-momentum-projection using an axially-deformed basis are performed up to high spins. Our calculated energy levels indicate a perfect collective-rotor behavior for the superdeformed yrast band. However, detailed analysis of the wave functions reveals that the high-spin structure is dominated by mixed 0-, 2-, and 4-quasiparticle configurations. The calculated electric quadrupole transition probabilities reproduce well the known experimental data and suggest a reduced, but still significant, collectivity in the high spin region. The deduced triaxial deformation parameters are small throughout the entire band, suggesting that triaxiality is not very important for this superdeformed band.

    nucl-thEPJA(2018)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE