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Nuclear Theory·nucl-th

Monday·June 6, 2016

5 papers—3 primary·2 cross-listed

All5Primary3Cross-lists2
  1. 01

    Hadron rapidity spectra within a hybrid model

    A. S. Khvorostukhin🇷🇺 · V. D. Toneev🇷🇺

    A 2-stage hybrid model is proposed that joins the fast initial state of interaction, described by the hadron string dynamics (HSD) model, to subsequent evolution of the expanding system at the second stage, treated within ideal hydrodynamics. The developed hybrid model is assigned to describe heavy-ion collisions in the energy range of the NICA collider under construction in Dubna. Generally, the model is in reasonable agreement with the available data on proton rapidity spectra. However, reproducing proton rapidity spectra, our hybrid model cannot describe the rapidity distributions of pions. The model should be improved by taking into consideration viscosity effects at the hydrodynamical stage of system evolution.

    nucl-thhep-phPhys.Part.Nucl.Lett.(2017)·13 citations
  2. 02

    Preequilibrium particle emissions and in-medium effects on the pion production in heavy-ion collisions

    Zhao-Qing Feng🇨🇳

    Within the framework of the Lanzhou quantum molecular dynamics (LQMD) transport model, pion dynamics in heavy-ion collisions near threshold energies and the emission of preequilibrium particles (nucleons and light complex fragments) have been investigated. A density, momentum and isospin dependent pion-nucleon potential based on the -hole model is implemented in the transport approach, which slightly leads to the increase of the ratio, but reduces the total pion yields. It is found that a bump structure of the ratio in the kinetic energy spectra appears at the pion energy close to the (1232) resonance region. The yield ratios of neutrons to protons from the squeeze-out particles perpendicular to the reaction plane are sensitive to the stiffness of nuclear symmetry energy, in particular at the high-momentum (kinetic energy) tails.

    nucl-thEPJA(2017)·13 citations
  3. 03

    Superfluid hydrodynamics in the inner crust of neutron stars

    Noël Martin🇫🇷 · Michael Urban🇫🇷

    The inner crust of neutron stars is supposed to be inhomogeneous and composed of dense structures (clusters) that are immersed in a dilute gas of unbound neutrons. Here we consider spherical clusters forming a BCC crystal and cylindrical rods arranged in a hexagonal lattice. We study the relative motion of these dense structures and the neutron gas using superfluid hydrodynamics. Within this approach, which relies on the assumption that Cooper pairs are small compared to the crystalline structures, we find that the entrainment of neutrons by the clusters is very weak since neutrons of the gas can flow through the clusters. Consequently, we obtain a low effective mass of the clusters and a superfluid density that is even higher than the density of unbound neutrons. Consequences for the constraints from glitch observations are discussed.

    nucl-thastro-ph.HEPRC(2016)·57 citations
  4. 04

    Dibaryons with two strange quarks and one heavy flavor in a constituent quark model

    Aaron Park🇰🇷 · Woosung Park🇰🇷 · Su Houng Lee🇰🇷

    We investigate the symmetry property and the stability of dibaryons containing two strange quarks and one heavy flavor with . We construct the wave function of the dibaryon in two ways. First, we directly construct the color and spin state of the dibaryon starting from the four possible SU(3) flavor state. Second, we consider the states composed of five light quarks, and then construct the wave function of the dibaryon by adding one heavy quark. The stability of the dibaryon against the strong decay into two baryons is discussed by using variational method in a constituent quark model with confining and hyperfine potential. We find that for all configurations with S=0,1,2, the ground states of the dibaryons are the sum of two baryons, and there are no compact bound state that is stable against the strong decay.

    ↳ hep-phnucl-thPRD(2016)·21 citations
  5. 05

    Two-gluon exchange contribution to elastic scattering and production of two-photons in ultraperipheral ultrarelativistic heavy ion and proton-proton collisions

    Mariola Klusek-Gawenda🇵🇱 · Wolfgang Schaefer🇵🇱 · Antoni Szczurek🇵🇱

    We discuss the two-gluon exchange contribution (formally three-loops) to elastic photon-photon scattering in the high-energy approximation. The elastic amplitude is given in the impact-factor representation for all helicity configurations and finite quark masses. We discuss the importance of including the charm quark, which contribution, due to interference, can enhance the cross section considerably. We investigate the contribution to the amplitude from the soft region, by studying its dependence on nonperturbative gluon mass. Helicity-flip contributions are shown to be much smaller than helicity-conserving ones. We identify region(s) of phase space where the two-gluon exchange contribution becomes important ingredient compared to box and nonperturbative VDM-Regge mechanisms considered in the literature. Consequences for the reaction are discussed. Several differential distributions are shown. A feasibility study to observe the effect of two-gluon exchange is presented. We perform a similar analysis for the reaction. Only by imposing severe cuts on and a narrow window on photon transverse momenta the two gluon contribution becomes comparable to the box contribution but the corresponding cross section is rather small.

    ↳ hep-phhep-exnucl-thPLB(2016)·38 citations

Affiliations

first authorsco-authorsvia INSPIRE