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arXiv 1002.0357nucl-th
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介质对重离子碰撞中带电π介子比的影响

Medium effects on charged pion ratio in heavy ion collisions

Che Ming Ko, Yongseok Oh, Jun Xu

备注：
11 pages, 4 figures, contribution to The International Workshop on Nuclear Dynamics in Heavy-Ion Reactions and the Symmetry Energy (IWND2009), Shanghai, China, 22-25 August, 2009
发表信息：
Int.J.Mod.Phys.E19:1763-1772,2010
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摘要：

最近，我们在δ共振核子空穴模型中研究了热密非对称核物质中的π能谱函数与核介质中π介子p波相互作用引起的π介子电荷的关系。在热模型中，这种依赖于同位旋的效应提高了富中子核物质中带负电荷的π介子与带正电荷的π介子的比率，并且这种效应与由于高密度下核对称能的理论预测刚度的不确定性而引起的效应相当。然而，如果我们也考虑手征微扰理论给出的π介子在核介质中的s波相互作用，这种效应就会逆转，结果是带负电荷的π介子与带正电荷的π介子的比率略有降低。我们的结果的相关性，以确定核对称性能量的比率产生的负，正电荷的π介子在重离子碰撞进行了讨论。

英文摘要：

We have recently studied in the delta-resonance--nucleon-hole model the dependence of the pion spectral function in hot dense asymmetric nuclear matter on the charge of the pion due to the pion p-wave interaction in nuclear medium. In a thermal model, this isospin-dependent effect enhances the ratio of negatively charged to positively charged pions in neutron-rich nuclear matter, and the effect is comparable to that due to the uncertainties in the theoretically predicted stiffness of nuclear symmetry energy at high densities. This effect is, however, reversed if we also take into account the s-wave interaction of the pion in nuclear medium as given by chiral perturbation theory, resulting instead in a slightly reduced ratio of negatively charged to positively charged pions. Relevance of our results to the determination of the nuclear symmetry energy from the ratio of negatively to positively charged pions produced in heavy ion collisions is discussed.

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