Insights on pion production mechanism and symmetry energy at high density

Abstract

The $N\Delta \to NN$ cross sections, which take into account the $\Delta$-mass dependence of M-matrix and momentum $p_{N\Delta }$, are applied on the calculation of pion production within the framework of the UrQMD model. Our study shows that UrQMD calculations with the $\Delta$-mass dependent $N\Delta \to NN$ cross sections enhance the pion multiplicities and decrease the ${\pi }^{-}/{\pi }^{+}$ ratios. By analyzing the time evolution of the pion production rate and the density in the overlapped region for Au+Au at the beam energy of 0.4A GeV, we find that the pion multiplicity probes the symmetry energy in the region of 1-2 times normal density. The process of pion production in the reaction is tracked including the loops of $NN\leftrightarrow N\Delta$ and $\Delta \leftrightarrow N\pi$, our calculations show that the sensitivity of ${\pi }^{-}/{\pi }^{+}$ to symmetry energy is weakened after 4-5 N-$\Delta$-$\pi$ loops in the pion production path, while the ${\pi }^{-}/{\pi }^{+}$ ratio in reactions at near threshold energies remains its sensitivity to the symmetry energy. By comparing the calculations to the FOPI data, we obtain a model dependent conclusion on the symmetry energy and the symmetry energy at two times normal density is $S(2{\rho }_0)$=38-73 MeV within $1\sigma$ uncertainties. Under the constraints of tidal deformability and maximum mass of neutron star, the symmetry energy at two times normal density is reduced to $48-58$ MeV and slope of symmetry energy $L=54-81$ MeV, and it is consistent with the constraints from ASY-EOS flow data.

11 pages, 9 fiigures

References in corpus (13)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• Results of the ASY-EOS experiment at GSI: The symmetry energy at suprasaturation density
• Constraints on the Symmetry Energy Using the Mass-Radius Relation of Neutron Stars
• Systematics of pion emission in heavy ion collisions in the 1A GeV regime
• Constraining the High-Density Behavior of Nuclear Symmetry Energy with the Tidal Polarizability of Neutron Stars
• Constraints on the symmetry energy and its associated parameters from nuclei to neutron stars
• Symmetry energy investigation with pion production from Sn+Sn systems
• Progress of Quantum Molecular Dynamics model and its applications in Heavy Ion Collisions
• Symmetry energy constraints from GW170817 and laboratory experiments
• Tides in merging neutron stars: Consistency of the GW170817 event with experimental data on finite nuclei
• Effects of pion potential and nuclear symmetry energy on the ${\pi }^{-}/{\pi }^{+}$ ratio in heavy-ion collisions at beam energies around the pion production threshold
• Effects of energy conservation on equilibrium properties of hot asymmetric nuclear matter
• Decomposition of sensitivity of the symmetry energy observables

Cited by in corpus (14)

• Dense Nuclear Matter Equation of State from Heavy-Ion Collisions
• Decoding the Density Dependence of the Nuclear Symmetry Energy
• Horizons: Nuclear Astrophysics in the 2020s and Beyond
• Constraining nuclear symmetry energy with the charge radii of mirror-pair nuclei
• Testing the phase transition parameters inside neutron stars with the production of protons and lambdas in relativistic heavy-ion collisions
• Influence of the treatment of initialization and mean-field potential on the neutron to proton yield ratios
• Studies of the equation-of-state of nuclear matter by heavy-ion collisions at intermediate energy in the multi-messenger era
• Equation of state of nuclear matter and neutron stars: Quark mean-field model versus relativistic mean-field model
• Elliptic flow in heavy-ion collisions at intermediate energy: the role of impact parameter, mean field potential, and collision term
• Auxiliary Function Approach for Determining Symmetry Energy at Supra-saturation Densities
• Correlation between nuclear temperatures and symmetry energy in sub-saturation
• Properties and microscopic structures of dense stellar matter in RMF models
• Constraining the Phase-Transition EoS using the Energy Dependence of Directed Flow
• Isospin blocking and its effects in heavy-ion collisions