Weak interaction axial form factors of the octet baryons in nuclear medium

TL;DR

This paper investigates how the axial-vector and induced pseudoscalar form factors of octet baryons change in nuclear medium using a covariant quark model, with implications for neutrino interactions and astrophysics.

Contribution

It extends previous vacuum form factor calculations to nuclear medium, incorporating medium modifications of hadron properties via the quark-meson coupling model.

Findings

Form factors are generally reduced in nuclear medium.

Reduction is more significant for light baryons and at higher densities.

Medium effects are milder for heavier octet baryons, especially at large Q^2.

Abstract

We study the axial-vector and the induced pseudoscalar form factors associated with the weak transitions between the octet baryon members in nuclear medium, using a covariant constituent quark model. We extend previous calculations of the axial transition form factors from the vacuum (free space) to the nuclear medium (symmetric nuclear matter). The extension of the model to the nuclear medium takes into account the modifications of the properties of hadrons in the medium (masses and coupling constants), as determined by the quark-meson coupling model. The axial-vector ($G_A$) and the induced pseudoscalar ($G_P$) form factors are evaluated for different values of the nuclear density $\rho$ in terms of the square transfer momentum $q^2= -Q^2$. We conclude that, in general, the $G_A$ and $G_P$ form factors are reduced in the nuclear medium. The reduction is stronger for light baryons and high densities. The medium modifications are milder for the heavier octet baryons, particularly at large $Q^2$. The calculations presented here can be used to estimate the cross sections of neutrino and antineutrino scattering with nucleus, and neutrino and antineutrino scattering with hyperons bound to a nucleus, as well as those in the cores of compact stars.