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.

传输模型不能同时解释最近关于 0.27 A GeV 的 Sn+Sn 中心碰撞的π介子多重性和π介子电荷比数据。这激发了对介子色散关系、介质中横截面和在阈能量附近或在同位旋不对称核物质中产生介子的阈下能量附近的衰变宽度的进一步研究。本研究采用单玻色子交换模型研究了等旋不对称核物质中的介子色散关系、介质中截面和阈值能量附近的衰变宽度。考虑到节能效果，中间截面在核介质中的 GeV。如果在传输模型模拟中考虑这种影响，则可以修改接近阈值能量的π介子多样性和比率的预测。