Examination of $N^{\ast }(1535)$ as a probe to observe the partial restoration of chiral symmetry in nuclear matter

Abstract

We investigate modifications of mass and decay width of $N^{\ast }(1535)$ in nuclear matter in a chiral symmetric way. The nucleon and $N^{\ast }(1535)$ are introduced by a parity doublet model, and nuclear matter is constructed by one-loop diagrams of the nucleon and $N^{\ast }(1535)$. The decay width of $N^{\ast }(1535)$ is studied respecting chiral symmetry. Our calculations show that the partial width of ${\Gamma }_{N^{\ast }\to N\pi }$ is slightly broadened by a collisional broadening, and that of ${\Gamma }_{N^{\ast }\to N\eta }$ is drastically suppressed at density. As a result, the total decay width ${\Gamma }_{\mathrm{tot}}$ gets small at density. These modifications, especially the drastic narrowing of partial width of ${\Gamma }_{N^{\ast }\to N\eta }$, together with the dropping of mass of $N^{\ast }(1535)$ provide experiments for observing the partial restoration of chiral symmetry in nuclear matter by means of $N^{\ast }(1535)$ resonance with useful information.

Comments: 16 pages, 13 figures