Measurement of high-Q2 neutral current deep inelastic e+p scattering cross sections with a longitudinally polarized positron beam at HERA

Abstract

Measurements of neutral current cross sections for deep inelastic scattering in e+p collisions at HERA with a longitudinally polarized positron beam are presented. The single-differential cross-sections dσ/dQ2, dσ/dx and dσ/dy and the reduced cross section σËœ are measured in the kinematic region Q2>185 GeV2 and y<0.9, where Q2 is the four-momentum transfer squared, x the Bjorken scaling variable and y the inelasticity of the interaction. The measurements are performed separately for positively and negatively polarized positron beams. The measurements are based on an integrated luminosity of 135.5 pb-1 collected with the ZEUS detector in 2006 and 2007 at a center-of-mass energy of 318 GeV. The structure functions FËœ3 and F3γZ are determined by combining the e+p results presented in this paper with previously published e-p neutral current results. The asymmetry parameter A+ is used to demonstrate the parity violation predicted in electroweak interactions. The measurements are well described by the predictions of the Standard Model. © 2013 American Physical Society.