Neutron Properties in the Medium

TL;DR

This paper predicts that the in-medium electric form factor ratio of a neutron increases at low momentum transfer, affecting neutron recoil polarization measurements, with implications for understanding nuclear medium modifications.

Contribution

It provides a model-independent prediction that the in-medium G_E/G_M ratio for neutrons increases at low Q^2 due to changes in the electric charge radius.

Findings

In-medium neutron G_E/G_M ratio increases at low Q^2.

Predicted increase in neutron recoil polarization cross-section.

Contrasts with medium effects on proton form factors.

Abstract

We demonstrate that for small values of momentum transfer, Q^2, the in-medium change of the G_E/G_M form factor ratio for a bound neutron is dominated by the change in the electric charge radius and predict in a model independent manner that the in-medium ratio will increase relative to the free result. This effect will act to increase the predicted cross-section for the neutron recoil polarization transfer process 4He(e,e'n)3He. This is in contrast to medium modification effects on the proton G_E/G_M from factor ratio, which act to decrease the predicted cross-section for the 4He(e,e'p)3H reaction. Experiments to measure the in-medium neutron form factors via neutron knockout reactions are currently feasible in the range 0.1 < Q^2 < 1 GeV^2.