Polarized EMC Effect in the QMC Model

TL;DR

This paper predicts a significant modification of the polarized structure function ratio in bound nucleons using the QMC model, suggesting a fundamental change in nucleon structure within nuclei that awaits experimental verification.

Contribution

It extends the QMC model to predict the polarized EMC effect, providing new insights into the in-medium modifications of nucleon spin structure.

Findings

The polarized structure function ratio g_1^*(x)/g_1(x) differs substantially from unity.

The polarized EMC effect shape and size are similar to the unpolarized case.

The model's predictions need experimental testing.

Abstract

The ratios of the in-medium to free nucleon structure functions for the unpolarized and polarized cases are obtained using the MIT bag model for the free case, along with the QMC model to incorporate the in-medium modifications of the structure functions. As discussed in earlier work, the observed nuclear EMC effect is reasonably well described. This gives us confidence to investigate the predictions of the model for the polarized EMC effect, the ratio $g_1^*(x)/g_1(x)$ for a bound proton to that of a free proton. This ratio is found to be substantially different from unity and very similar in shape and size to that found in the unpolarized case. This prediction of such a fundamental change in the valence structure of a bound nucleon needs to be tested experimentally at the earliest opportunity.