Measurement of high-Q^2 neutral current deep inelastic e^- p scattering cross sections with a longitudinally polarised electron beam at HERA

TL;DR

This paper reports precise measurements of neutral current deep inelastic e^- p scattering cross sections at high Q^2 with polarized electrons at HERA, confirming Standard Model predictions and exploring electroweak parity violation effects.

Contribution

It provides new measurements of differential cross sections and structure functions in polarized e^- p scattering, enhancing understanding of electroweak interactions at high energies.

Findings

Measurements agree with Standard Model predictions.

Determination of structure functions xF_3 and xF_3^{A3}.

Observation of parity-violating effects at high Q^2.

Abstract

Measurements of the neutral current cross sections for deep inelastic scattering in e^- p collisions at HERA with a longitudinally polarised electron beam are presented. The single-differential cross-sections dsigma/dQ^2, dsigma/dx and dsigma/dy and the double-differential cross sections in Q^2 and x are measured in the kinematic region y < 0.9 and Q^2 > 185 GeV^2 for both positively and negatively polarised electron beams and for each polarisation state separately. The measurements are based on an integrated luminosity of 169.9 pb^-1 taken with the ZEUS detector in 2005 and 2006 at a centre-of-mass energy of 318 GeV. The structure functions xF_3 and xF_3^{\gamma Z} are determined by combining the e^- p results presented in this paper with previously measured e^+ p neutral current data. The asymmetry parameter A^- is used to demonstrate the parity violating effects of electroweak interactions at large spacelike photon virtuality. The measurements agree well with the predictions of the Standard Model.