Pion electromagnetic charge radii and rho-meson mass shift at finite density

TL;DR

This paper studies how the pion charge radius and rho-meson mass change at finite density using a nonlocal chiral quark model, finding that the rho-meson mass decreases by about 10% at normal nuclear density.

Contribution

It provides a theoretical calculation linking pion charge radius expansion to rho-meson mass dropping at finite density using the instanton vacuum model.

Findings

Pion charge radius increases with quark chemical potential.

Rho-meson mass drops by approximately 10% at normal nuclear matter density.

Results agree with recent KEK measurements.

Abstract

We investigate the pion electromagnetic charge radii and mass dropping of the rho meson at finite density. We first calculate the pion charge radii within the framework of the nonlocal chiral quark model from the instanton vacuum both at zero and finite densities. In order to relate the change of the pion charge radius to that of the rho-meson mass at finite density, we employ the vector-meson dominance for the pion electromagnetic form factor. It turns out that the pion charge radius is getting larger as the quark chemical potential increases. As a result, the rho-meson mass falls off as the quark chemical potential grows and is found to be dropped by about 10% at normal nuclear matter density: m*_rho/m_rho ~ 1 - 0.12 mu_B/mu_0, which is compatible to the results of the measurement at the KEK recently.