In-medium pion dispersion relation and medium correction of near the threshold energy of pion production * *Supported by National Key R&D Program of China (2018 YFA0404404) and National Natural Science Foundation of China (11875323, 11875125, 11475262, 11961141003, 11790323, 11790324, 11790325) and the Continuous Basic Scientific Research Project (WDJC-2019-13,No BJ20002501)

Abstract

Transport models cannot simultaneously explain very recent data on pion multiplicities and pion charged ratios from central collision of Sn+Sn at 0.27 A GeV. This stimulates further investigations on the pion dispersion relation, in-medium cross sections, and decay widths near the threshold energy or at subthreshold energy of pion production in isospin asymmetric nuclear matter. In this study, the pion dispersion relation, in-medium cross section, and decay width near the threshold energy are investigated in isospin asymmetric nuclear matter by using the one-boson-exchange model. With the consideration of the energy conservation effect, the in-medium cross sections are enhanced at GeV in a nuclear medium. The prediction of pion multiplicity and ratios near the threshold energy could be modified if this effect is considered in transport model simulations.