Collision integral with momentum-dependent potentials and its impact on pion production in heavy-ion collisions

Abstract

The momentum dependence of the nucleon mean-field potential in a wide momentum range can be an important factor to determine the $\Delta$ resonance and pion production in intermediate-energy heavy-ion collisions. In particular, in neutron-rich systems such as ${}^{132}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ collisions, we need to carefully treat the momentum dependence because the neutron and proton potentials can have different momentum dependence, as characterized at low momenta by effective masses. In the present work, we rigorously calculate the collision terms of $NN\leftrightarrow N\Delta$ and $\Delta \leftrightarrow N\pi$ processes with the precise conservation of energy and momentum under the presence of momentum-dependent potentials for the initial and final particles of the process. The potentials affect not only the threshold condition for the process but also the cross section in general as a function of the momenta of the initial particles, which is treated in a natural way in the present work. Calculations are performed by combining the nucleon dynamics obtained by the antisymmetrized molecular dynamics (AMD) model with a newly developed transport code which we call sJAM. The calculated results for central ${}^{132}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ collisions at 270 MeV/nucleon clearly show that the momentum dependence of the neutron and proton potentials has a significant impact on the $NN\to N\Delta$ process, and this information is strongly reflected in the charged pion ratio (${\pi }^{-}/{\pi }^{+}$). We also investigate the effects of the high-density symmetry energy and the isovector part of the potential of $\Delta$ resonances on pion production, which we find are relatively small compared to the effect of the momentum dependence of the neutron and proton potentials.

18 pages, 13 figures, 1 table

References in corpus (12)

• Constraining Neutron-Star Matter with Microscopic and Macroscopic Collisions
• Probing the Symmetry Energy with the Spectral Pion Ratio
• Isospin effects on sub-threshold kaon production at intermediate energies
• Dynamics of clusters and fragments in heavy-ion collisions
• Comparison of Heavy-Ion Transport Simulations: Mean-field Dynamics in a Box
• Decoding the Density Dependence of the Nuclear Symmetry Energy
• Symmetry energy investigation with pion production from Sn+Sn systems
• $\Delta$-admixed neutron stars: spinodal instabilities and dUrca processes
• Effects of energy conservation on equilibrium properties of hot asymmetric nuclear matter
• Exploring the effects of Delta Baryons in magnetars
• Studies of the equation-of-state of nuclear matter by heavy-ion collisions at intermediate energy in the multi-messenger era
• Isoscaling in central Sn+Sn collisions at 270 MeV/u

Cited by in corpus (3)

• Neutron Star Radii from Laboratory Experiments
• Activation of momentum fluctuations in wave packet molecular dynamics: Impacts on momentum distributions of projectilelike fragments
• Angular momentum conservation and pion production in intermediate-energy heavy-ion collisions