Gamow-Teller transitions and the spin EMC effect: the Bjorken sum-rule in medium

TL;DR

This paper investigates how nuclear medium affects the spin structure of nucleons, revealing a significant quenching of axial charge and implications for the Bjorken sum-rule and spin-dependent observables in nuclei.

Contribution

It provides new insights into medium modifications of nucleon spin structure, challenging models based solely on short-range correlations.

Findings

Axial charge $g_A^{(3)}$ is quenched by about 20% in large nuclei.

Spin structure modifications disfavor models based only on short-range correlations.

Gerasimov-Drell-Hearn integral is expected to be strongly enhanced in medium.

Abstract

Gamow-Teller transitions in nuclei tell us that the nucleon's axial charge $g_A^{(3)}$ is quenched in large nuclei by about 20%. This result tells us that the spin structure of the nucleon is modified in nuclei and disfavours models of the medium dependence of parton structure based only on nucleon short range correlations in nuclei. For polarized photoproduction the Gerasimov-Drell-Hearn integral is expected to be strongly enhanced in medium.