Transverse momentum resummation effects inW+W−measurements

Abstract

The ${W}^{+}{W}^{\ensuremath{-}}$ cross section has remained one of the most consistently discrepant channels compared to Standard Model (SM) predictions at the LHC, measured by both ATLAS and CMS at 7 and 8 TeV. Developing a better modeling of this channel is crucial to understanding properties of the Higgs and potential new physics. In this paper we investigate the effects of next-to-next-to-leading-log transverse momentum resummation in measuring the ${W}^{+}{W}^{\ensuremath{-}}$ cross section. In the formalism we employ, transverse momentum resummation does not change the total inclusive cross section but gives a more accurate prediction for the ${p}_{T}$ distribution of the diboson system. By reweighting the ${p}_{T}$ distribution of events produced by Monte Carlo generators, we find a systematic shift that decreases the experimental discrepancy with the SM prediction by approximately 3%--7% depending on the Monte Carlo generator and parton shower used. The primary effect comes from the jet-veto cut used by both experiments. We comment on the connections to jet-veto resummation and other methods the experiments can use to test this effect. We also discuss the correlation of resummation effects in this channel with other diboson channels. Ultimately ${p}_{T}$ resummation improves the agreement between the SM and experimental measurements for most generators but does not account for the measured $\ensuremath{\sim}20%$ difference with the SM, and further investigations into this channel are needed.