Emission of High-Energy Protons and Photons in Heavy-Ion Collisions Treated on the Basis of a Hydrodynamic Approach with
- PDF / 1,196,731 Bytes
- 9 Pages / 612 x 792 pts (letter) Page_size
- 25 Downloads / 163 Views
CLEI Theory
Emission of High-Energy Protons and Photons in Heavy-Ion Collisions Treated on the Basis of a Hydrodynamic Approach with a Nonequilibrium Equation of State A. T. D’yachenko1), 2)* and I. A. Mitropolsky2) Received December 25, 2019; revised December 25, 2019; accepted December 25, 2019
Abstract—A hydrodynamic approach involving a nonequilibrium equation of state is used in describing heavy-ion collisions at medium and intermediate energies. The double differential cross sections for proton and photon emission in collisions of various nuclei are calculated in developing this approach with allowance for nuclear-viscosity effects and amendments introduced by the microcanonical distribution. The results agree everywhere, including the cumulative region of the spectrum, with available experimental data on the emission of high-energy particles. The approach in question permits reproducing high-momentum distributions of protons from the reaction 12 С + 9 Be → p + X at the 12 С ion energies of 300, 600, 950, and 2000 MeV per nucleon and the energy spectra of hard photons from the reaction 12 С + 9 Be → γ + X at the 12 С ion energies of 2.0 and 3.2 GeV per nucleon. DOI: 10.1134/S1063778820040080
1. INTRODUCTION The techniques of calculations of heavy-ion collisions have reached a rather high level to date. Along with molecular dynamics methods and methods of solving the dynamical Boltzmann equation, nuclear hydrodynamics (see, for example, [1–6]) is an efficient tool for describing the interaction of heavy ions at medium and intermediate energies. At medium en¨ ergies of colliding ions, Stocker and Greiner [1] used the equilibrium equation of state (EOS) valid under the assumption of local thermodynamic equilibration. In the energy region of the NICA (Nuclotron-based Ion Collider fAсility) accelerator complex under construction at the Joint Institute for Nuclear Research (JINR, Dubna), a successful description of experimental data was obtained within one-fluid relativistic hydrodynamics [2]. At high energies, use is made of two-fluid [3] and three-fluid [4] relativistic hydrodynamics with allowance for a deviation of the distribution function from a locally equilibrium one. For the NICA energies, Khvorostukhin and Toneev [5, 6] proposed employing a hybrid model including a fast nonequilibrium kinetic collision stage and a subsequent description of the dynamics of a nucleus– nucleus collision on the basis of the equilibrium relativistic hydrodynamics of a perfect fluid. In our 1)
Petersburg State Transport University, St. Petersburg, Russia. 2) Petersburg Nuclear Physics Institute, National Research Center Kurchatov Institute, Gatchina, Russia. * E-mail: [email protected]
studies reported in [7–12], it was shown that a local thermodynamic equilibrium is not established immediately in heavy-ion collisions, since the nonequilibrium distribution-function component leading to the formation of a collisionless shock wave similar to collisionless shock waves in the calculations on the basis of the time-dependent Hartree–Foc
Data Loading...
