Nuclear Effects on R = sigma_L / sigma_T in Deep-Inelastic Scattering

TL;DR

This study measures nuclear effects on the ratio R = sigma_L / sigma_T in deep-inelastic scattering across various nuclei, revealing an A-dependence at low x and Q^2, with implications for understanding nuclear modifications.

Contribution

First measurement of R ratio in deep-inelastic scattering for nitrogen and helium nuclei at low x and Q^2, highlighting nuclear dependence.

Findings

Observed differences in R for 14N and 3He compared to deuterium at low x and Q^2.

Identified A-dependence of R at low x and Q^2.

Data suggest nuclear modifications affect the longitudinal to transverse cross section ratio.

Abstract

Cross section ratios for deep-inelastic scattering from 14N and 3He with respect to 2H have been measured by the HERMES experiment at DESY using a 27.5 GeV positron beam. The data cover a range in the Bjorken scaling variable x between 0.013 and 0.65, while the negative squared four-momentum transfer Q^2 varies from 0.5 to 15 GeV^2. The data are compared to measurements performed by NMC, E665, and SLAC on 4He and 12C, and are found to be different for x < 0.06 and Q^2 < 1.5 GeV^2. The observed difference is attributed to an A-dependence of the ratio R = sigma_L / sigma_T of longitudinal to transverse deep-inelastic scattering cross sections at low x and low Q^2.