One-loop weak corrections to hadronic production of Z bosons at large transverse momenta

To match the precision of present and future measurements of Z-boson production at hadron colliders, electroweak radiative corrections must be included in the theory predictions. In this paper we consider their effect on the transverse momentum (PT) distribution of Z bosons, with emphasis on large PT. We evaluate, analytically and numerically, the full one-loop corrections for the parton scattering reaction qq -> Zg and its crossed variants. In addition we derive compact approximate expressions which are valid in the high-energy region, where the weak corrections are strongly enhanced by logarithms of s/M-W(2). These, expressions include quadratic and single logarithms as well as those terms that are not logarithmically enhanced. This approximation, which confirms and extends earlier results obtained to next-to-leading logarithmic accuracy, permits to reproduce the exact one-loop corrections with high precision. Numerical results are presented for proton-proton and proton-anti proton collisions. The corrections are negative and their size increases with PT. For the Tevatron they amount up to -7% at 300 GeV. For the LHC, where transverse momenta of 2 TeV or more can be reached, corrections up to -40% are observed. We also include the dominant two-loop effects of up to 8% in our final LHC predictions. (c) 2005 Published by Elsevier B.V.