Probing Chiral Symmetry of Nucleon by Threshold ηπ Production

The time-evolution of quantum meson fields is investigated in the linear sigma model by means of the time-dependent variational approach with a squeezed state. The chiral condensate, which is a mean field of the quantum meson fields, and quantum fluctuations around it are treated self-consistently in this approach. The attention is paid to the description of the relaxation process of the chiral condensate, where the energy stored in the mean field configuration flows to the fluctuation modes. It is shown that the quantum fluctuations play an important role in describing this relaxation process.is investigated in order to determine chiral properties of the nucleon. The eta can be used as a probe for the negative parity nucleon N^* ≡ N^*(1535), produced in the intermediate state. The coupling of the low energy pion in the final state is then used to extract the sign of the Yukawa coupling, g_πN^*N^*, which distinguishes the two realizations of chiral symmetry, naive and mirror, for the nucleon.