Measurement of High-Q^2 Neutral-Current e^+p Deep Inelastic Scattering Cross-Sections at HERA

Abstract

The e^+p neutral-current deep inelastic scattering differential cross-sections $d\ddot{I}ƒ/d{Q}^2$, for Q^2 > 400 GeV^2, $d\ddot{I}ƒ/dx$ and $d\ddot{I}ƒ/dy$, for Q^2 > 400, 2500 and 10000 GeV^2, have been measured with the ZEUS detector at HERA. The data sample of 47.7 pb^-1 was collected at a center-of-mass energy of 300 GeV. The cross-section, $d\ddot{I}ƒ/d{Q}^2$, falls by six orders of magnitude between Q^2 = 400 and 40000 GeV^2. The predictions of the Standard Model are in very good agreement with the data. Complementing the observations of time-like Z^0 contributions to fermion-antifermion annihilation, the data provide direct evidence for the presence of Z^0 exchange in the space-like region explored by deep inelastic scattering.

28 pages including 8 figures; final version for Euro. Phys. J