High-Q^2 neutral current cross sections in e^+p deep inelastic scattering at sqrt{s}=318 GeV

TL;DR

This ZEUS study provides a precise measurement of neutral-current deep inelastic e^+ p scattering at sqrt{s}=318 GeV, covering 200–30000 GeV^2 in Q^2 and 0.005–0.65 in x. It employs a comprehensive MC framework and double-angle kinematic reconstruction to extract d^2sigma/dx dQ^2, along with single-differential cross sections and reduced cross sections, confirming SM predictions that include both photon and Z-boson exchange. The analysis demonstrates a clear Z-exchange effect at high Q^2, achieves a robust F2^{em} extraction by combining with 300 GeV data, and shows consistency with H1 and fixed-target measurements across a wide kinematic range. Overall, the results validate the SM description of NC DIS and provide high-precision inputs for proton PDFs such as ZEUS-S, CTEQ6D, and MRST(01).

Abstract

Cross sections for e^+p neutral current deep inelastic scattering have been measured at a centre-of-mass energy of sqrt{s}=318 GeV with the ZEUS detector at HERA using an integrated luminosity of 63.2 pb^-1. The double-differential cross section, d^2sigma/dxdQ^2, is presented for 200 GeV^2 < Q^2 < 30000 GeV^2 and for 0.005 < x < 0.65. The single-differential cross-sections dsigma/dQ^2, dsigma/dx and dsigma/dy are presented for Q^2 > 200 GeV^2. The effect of Z-boson exchange is seen in dsigma/dx measured for Q^2 > 10000 GeV^2. The data presented here were combined with ZEUS e^+p neutral current data taken at sqrt{s}=300 GeV and the structure function F_2^{em} was extracted. All results agree well with the predictions of the Standard Model.