The a1(1260) as a rho pi resonance in nuclear matter

TL;DR

This paper investigates how the a1(1260) resonance behaves in nuclear matter, showing it broadens significantly with density, and explores implications for chiral symmetry restoration.

Contribution

It introduces a theoretical model for the in-medium a1(1260) resonance based on a coupled channel chiral approach with medium modifications.

Findings

a1(1260) broadens with increasing nuclear density

Medium effects significantly alter rho and pi propagators

Results suggest partial chiral symmetry restoration in nuclear matter

Abstract

We present a theoretical study of the properties of the a1(1260) axial-vector resonance in a cold nuclear medium. In the vacuum, the a1(1260) resonance is generated dynamically from the interactions of a pseudoscalar and vector meson (rho pi and K barK*) in a coupled channel chiral unitary approach. Medium effects are implemented through the modification of the rho and pi propagators at finite nuclear density from well established microscopic many-body calculations. The in-medium pion spectral function accounts for the coupling to N-hole and Delta-hole excitations including short range correlations, whereas the in-medium rho incorporates modifications of its virtual pion cloud as well as direct resonance-hole excitations. The resulting in-medium a1(1260) exhibits significant broadening with increasing density as reflected in the rho pi scattering amplitude. The possible relation of our results with partial restoration of chiral symmetry in nuclear matter is discussed in terms of in-medium Weinberg sum rules.