Measurement of high-Q^2 deep inelastic scattering cross sections with a longitudinally polarised positron beam at HERA

TL;DR

This paper reports measurements of high-Q^2 deep inelastic scattering cross sections in e^+p collisions with a polarised positron beam at HERA, testing Standard Model predictions and searching for right-handed currents.

Contribution

It provides the first measurements of these cross sections with a longitudinally polarised positron beam at high Q^2, comparing results to Standard Model expectations.

Findings

Measured cross sections are consistent with Standard Model predictions.

No evidence for right-handed charged currents within experimental uncertainties.

Data supports the absence of right-handed charged currents in the Standard Model.

Abstract

The cross sections for charged and neutral current deep inelastic scattering in e^+p collisions with a longitudinally polarised positron beam have been measured using the ZEUS detector at HERA. The results, based on data corresponding to an integrated luminosity of 23.8 pb^-1 at sqrt(s) = 318 GeV, are given for both e^+p charged current and neutral current deep inelastic scattering for both positive and negative values of the longitudinal polarisation of the positron beam. Single differential cross sections are presented for the kinematic region Q^2 > 200 GeV^2 . The measured cross sections are compared to the predictions of the Standard Model. A fit to the data yields sigma^CC (P_e = -1) = 7.4 +/- 3.9 (stat.) +/- 1.2 (syst.) pb, which is consistent within two standard deviations with the absence of right-handed charged currents in the Standard Model.