Possible medium effects on η-π^0 mixing and η\rightarrow π^0 π^+ π^- decay in the asymmetric nuclear matter

It is known that the decay process η\rightarrowπ^0π^+π^- in free space is possible due to the isospin-symmetry breaking in Quantum Chromodynamics (QCD), i.e., the small mass difference between u and d quarks: The small width is intimately related with the mixing property between ηand π^0 mesons for which the chiral anomaly play a role. In asymmetric nuclear matter such as heavy nuclei, isospin-symmetry breaking is large and it is expected that the mixing property of the mesons changes significantly and the above-mentioned decay width of the ηcreated in such a medium may be enhanced. This is an intriguing possibility to revealing a medium effect on a hadron in nuclei. We apply the in-medium chiral perturbation theory to estimate the modification of the η-π^0 mixing angle and the partial width of ηπ^0π^+π^- in asymmetric nuclear matter as a function of the isospin asymmetry. We find that these quantities can be greatly enhanced in neutron-rich matter, which should be deteactable in experiment.

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