Influence of differential elastic nucleon-nucleon cross section on stopping and collective flow in heavy-ion collisions at intermediate energies

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In this paper, the in-medium N N → N ∆ cross section is calculated in the framework of the one-boson exchange model by including the isovector mesons, i.e. δ and ρ mesons. Due to the isospin exchange in the N N → N ∆ process, the vector self-energies of the outgoing particles are modified relative to the incoming particles in isospin asymmetric nuclear matter, and it leads to the effective energies of the incoming N N pair being different from the outgoing N ∆ pair. This effect is investigated in the calculation of the in-medium N N → N ∆ cross section. With the corrected energy conservation, the cross sections of the ∆ ++ and ∆ + channels are suppressed, and the cross sections of the ∆ 0 and ∆ − channels are enhanced relative to the results obtained without properly considering the potential energy changes. Our results further confirm the dependence of medium correction factor, R = σ * N N →N ∆ /σ free N N →N ∆ , on the charge state of N N → N ∆ especially around the threshold energy, but the isospin splitting of medium correction factor R becomes weak at high beam energies.

Section: Introductionmentioning

confidence: 99%

Effect of energy conservation on the in-medium NN→NΔ cross section in isospin-asymmetric nuclear matter

Cui

Zhang

2018

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“…[39]. The experimental data of heavy-ion collisions in intermediate energies can be reproduced reasonably well by this model [39][40][41][42][43][44][45].…”

Section: Magnetic Field Calculations In Urqmdmentioning

confidence: 52%

Effect of internal magnetic field on collective flow in heavy ion collisions at intermediate energies

Sun

Wang

et al. 2019

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The properties of nuclear matter under extreme conditions of high temperature, density and isospin-asymmetry have attracted wide attentions in recent years. At present, heavy ion reactions in combination with corresponding model simulations are one of the most important ways to investigate this subject. It is known that a strong magnetic field can be created in heavy ion collisions. However, its effect on the motion of charged particles is usually neglected in previous transport model simulations. In this work, within the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model, the temporal evolution and spatial distribution of the internal magnetic field are calculated. The magnetic field strength is found to reach about eB ≈ 470 MeV 2 (B ≈ 8 × 10 16 G) for Au+Au collisions at E lab =1 GeV/nucleon with impact parameter of 7 fm.The magnetic field in Cu+Au collisions exhibits somewhat different spatial distribution from that in Au+Au collisions. The magnetic field is found to affect the directed flow of pions at forward and backward rapidities to some extent, dependent of the impact parameter and beam energy while the effect on the elliptic flow is small. This suggests that, because π mesons produced in heavy ion collisions at intermediate energies are considered as a sensitive probe for the nuclear symmetry energy, it is necessary to consider the effect of the internal magnetic field. 25.75.Ld

“…The total Hamilton H consists of the kinetic energy and the effectively two-body nuclear potential energy as well as the Coulomb potential energy. In the present version of the UrQMD model [43][44][45][46], the mean field potential part is derived from the Skyrme energy density functional, and the SV-mas08 interaction with a corresponding incompressibility K 0 =233 MeV is employed. The Coulomb potential of all charged particles and the momentum dependent interactions for all baryons are taken in the same way as the conventional QMD model [13,47,48].…”

Section: The Pion Potential In Urqmdmentioning

confidence: 99%

Collective flows of pions in Au+Au collisions at energies 1.0 and 1.5 GeV/nucleon

Liu

Wang

et al. 2018

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Based on the newly updated version of the ultrarelativistic quantum molecular dynamics (UrQMD) model, the pion potentials obtained from the in-medium dispersion relation of the ∆hole model and from the modified phenomenological approach are further introduced. Both the rapidity y 0 and transverse-velocity u t0 dependence of directed v 1 and elliptic v 2 flows of π + and π − charged mesons produced from Au+Au collisions at two beam energies of 1.0 GeV/nucleon and 1.5 GeV/nucleon and within a large centrality region of 0 < b 0 < 0.55 are scanned. Calculations with pion potentials as well as without considering the pion potential are compared to the newly experimental data released by the FOPI collaboration at GSI. It is found that the directed flow is more sensitive to the pion potential than the elliptic one, and the attractive pion potential from the phen.B mode of the phenomenological approach is too strong to describe the flow data and can be safely ruled out. The relatively weak pion potential from the ∆-hole model can supply a good description for the FOPI data of both flows as functions of both centrality and rapidity. A two-peak/valley structure occurs in the transverse-velocity dependent directed flow but the elliptic flow drops monotonously with increasing u t0 . Finally, both v 1 and v 2 flows with large u t0 from semi-central heavy ion collisions can be taken as sensitive probes for the pion potential. 25.75.Ld