利用π^-/π^+探测对称能的高密行为

Study on Stiffness of the Symmetry Energy at High Densities by π^-/π^+ Ratio

利用同位旋和动量相关的IBUU相对论强子输运模型,以132Sn+124Sn碰撞在E/A=400MeV,b=1fm时为例,研究了在3种不同的对称能作用下发射粒子谱中π-/π+的比率随时间和横动量的演化.计算结果表明,π-/π+的比率与核物质对称能的硬度有一个反向变化关系.由于π介子主要来自于核反应形成的高密区,因此π-/π+的比率可以作为精确研究核物质对称能高密行为的一个探针.通过与实验数据的比较,就能够得出比以往更精确的关于对称能高密行为的重要信息.

Using the isospin- and momentum-dependent transport model, for three different symmetry energies, we have calculated the π-/π+ ratio as a function of time and transverse-momentum in central 132Sn + 124Sn collision at Ebeam/A = 400 MeV. The results show that the π-/π+ ratios is very sensitive to the stiffness of the symmetry energy. Thus we can probe the stiffness of the symmetry energy at high densities by using the π-/π+ ratio at different time or transverse momentum more accurately than before. Comparing experimental data with the calculations will reveal crucial information about the stiffness of the symmetry energy more accurately.