Measurement of R=\sigma_L/\sigma_T in Deep-Inelastic Scattering on Nuclei

TL;DR

This study measures the ratio of longitudinal to transverse deep-inelastic scattering cross sections on various nuclei, finding the ratio to be consistent with unity across a broad kinematic range, providing insights into nuclear effects in DIS.

Contribution

It presents new measurements of the R ratio in DIS on nuclei over a wide x and Q^2 range, extending previous data to lower epsilon values and comparing results across different nuclei.

Findings

R ratio is consistent with unity across measured kinematics.

Data differ from previous measurements at low x and Q^2.

Results provide new insights into nuclear modifications in DIS.

Abstract

Cross section ratios for deep-inelastic scattering from $^3$He, $^{14}$N and $^{84}$Kr with respect to $^2$H have been measured by the HERMES collaboration at DESY using a 27.5 GeV positron beam. The data cover a range in the Bjorken scaling variable $x$ between 0.010 and 0.65, the negative squared four-momentum transfer $Q^2$ varies from 0.5 to 15 GeV$^2$, while at small values of $x$ and $Q^2$, the virtual photon polarisation parameter $\epsilon$ extends to lower values than previous measurements. From the dependence of the data on $\epsilon$, values for $R_A/R_D$ with $R$ the ratio $\sigma_L / \sigma_T$ of longitudinal to transverse DIS cross sections have been derived and found to be consistent with unity. %The data are compared to measurements performed by NMC, E665, and SLAC %on $^4$He and $^{12}$C, and are found to be different for %$x <$ 0.06 and $Q^2 <$ 1.5 GeV$^2$.