Transverse momentum resummation effects inW+W−measurements

Abstract

The W þ W − 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 þ W − 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 ∼20% difference with the SM, and further investigations into this channel are needed.

On the excess in the inclusive W + W − → l + l − ν ν ¯ $$ {W}^{+}{W}^{-}\ \to\ {l}^{+}{l}^{-}\nu \overline{\nu} $$ cross section

“…It is well-known that, in the presence of a jet-veto, fixed-order calculations typically underestimate the true theoretical uncertainty, and a more sophisticated procedure should be used in order to assess the uncertainty [15,16]. Since at the moment the by far dominant uncertainty is the systematic one, and since several theoretical improvements are now possible on the theory numbers quoted above (inclusion of NNLL resummation effects [26,27] matched to exact NNLO predictions [17], and NNLL threshold resummation in the total cross section [25]), we do not try to quantify the theory error in a more precise way. Yet, we observe that there is no sizable tension between NLO theory and experiment within the large systematic uncertainties.…”

The gauge-Higgs legacy of the LHC Run I

“…We compare these results to the experimental predictions, defining a bin-by-bin correction factor. It accounts for phase-space dependent corrections either from detector effects or from higher order corrections [67][68][69][70][71][72]. These correction factors we apply to our simulated W V distributions in the presence of the anomalous TGVs, based on an in-house MadGraph5 implementation of the operators constructed with FeynRules [73].…”

“…[57]. To ensure this, we introduce a bin-by-bin correction factor to account for differences in the selection procedure because of detector effects as well as higher order corrections to the cross section prediction [67][68][69][70][71][72].…”

Diphoton production at hadron colliders: transverse-momentum resummation at next-to-next-to-leading logarithmic accuracy

“…The formalism is valid for a generic process in which a high-mass system of non strongly-interacting particles is produced in hadron-hadron collisions. The method has so far been applied to the production of the Standard Model (SM) Higgs boson [44,45,[47][48][49], Higgs boson production in bottom quark annihilation [50], Higgs boson production via gluon fusion in the MSSM [51], single vector bosons at NLL+LO [52] and at NNLL+NLO [53], W W [54,55] and ZZ [56] pairs, slepton pairs [57], and DY lepton pairs in polarized collisions [58][59][60][61].…”