Investigation of Medium Modifications to $^{12}$C Structure Functions in the Resonance Region

TL;DR

This study measures how the ratio of longitudinal to transverse structure functions in carbon nuclei differs from deuterium in the resonance region, revealing nuclear modifications across different structure functions.

Contribution

It provides the first detailed measurements of nuclear effects on the $F_L$ to $F_1$ ratio in the resonance region, expanding understanding beyond the well-studied deep inelastic scattering region.

Findings

Regions where $R_C > R_D$ were observed.

Nuclear modifications differ among $F_2$, $F_1$, and $F_L$.

Results suggest complex nuclear effects in the resonance region.

Abstract

We present results from a high precision experimental study of the nuclear modification of the longitudinal ($F_L$) to transverse ($F_1$) structure function ratio for bound nucleons in the resonance region. The inclusive electron scattering cross sections were measured in Jefferson Lab Experimental Hall C on carbon and deuterium nuclei for a large range of kinematics, allowing for separations of the longitudinal and transverse structure functions to be performed at a range of four-momentum transfer values $0.5 \le Q^2 \le$ 3.75 GeV$^2$. In contrast to the significant body of measurements of the nuclear modification of the $F_2$ structure function in the deep inelastic scattering region, there is very little on $F_L$ and $R = F_L / 2xF_1$ in the region of the nucleon resonances. In this paper we present measurements of the nuclear effect on $R$ for $^{12}$C ($R_C$) relative to deuterium ($R_D$). These results indicate regions in which in $R_C>R_D$, requiring that the nuclear modifications be different in all three structure functions, $F_2$, $F_1$ and $F_L$.