Extraction of R = sigma_L/sigma_T from CCFR nu_mu-Fe and nubar_mu-Fe differential cross sections

TL;DR

This paper presents measurements of the ratio R = sigma_L / sigma_T from neutrino-iron scattering, showing consistency with QCD predictions at high Q^2 and providing new data at low x and Q^2 where nuclear effects are observed.

Contribution

It provides the first measurements of R in the low x and Q^2 < 1 GeV^2 region for neutrino scattering, extending understanding of nuclear effects in this regime.

Findings

R measurements agree with QCD at Q^2 > 1 GeV^2

No deviations from QCD expectations at high x

First data on R at low x and Q^2 < 1 GeV^2 for neutrino scattering

Abstract

We report on the extraction of R=sigma_L/sigma_T from CCFR nu_mu-Fe and nubar_mu-Fe differential cross sections. The CCFR differential cross sections do not show the deviations from the QCD expectations that are seen in the CDHSW data at very low and very high x. R as measured in nu_mu scattering is in agreement with R as measured in muon and electron scattering. All data on R for Q^2 > 1 GeV^2 are in agreement with a NNLO QCD calculation which includes target mass effects. We report on the first measurements of R in the low x and Q^2 < 1 GeV^2 region (where an anomalous large rise in R for nuclear targets has been observed by the HERMES collaboration).