Eta-prime bound states in nuclei and partial restoration of chiral symmetry

TL;DR

This paper explores how partial restoration of chiral symmetry in nuclear matter can lead to a significant reduction in the eta-prime meson mass, potentially forming bound states observable in experiments.

Contribution

It demonstrates that chiral symmetry restoration causes a notable eta-prime mass decrease and predicts the formation of eta-prime bound states in nuclei as experimental signatures.

Findings

Eta-prime mass reduces by about 100 MeV at nuclear saturation density.

Formation spectrum of eta-prime bound states is calculable and observable.

Suppression of U(1)A anomaly effect is key to mass reduction.

Abstract

We discuss the in-medium mass of the eta-prime meson under partial restoration of chiral symmetry. The chiral SU(3)\otimes SU(3) symmetry tells us the flavor singlet pseudoscalar meson eta-prime should degenerate with the octet $\eta$ meson in the SU(3) flavor limit, when chiral symmetry is restored in spite of U(1)A anomaly in the flavor single axial current. The suppression of the anomaly effect induces an order of 100 MeV reduction for the eta-prime mass at the saturation density without introducing a large absorption width. We show the formation spectrum of the eta-prime mesonic bound state in a nucleus as a possible observation of the eta-prime mass reduction.