Study of exclusive two-photon production of W(+)W(-) in pp collisions at sqrt(s) = 7 TeV and constraints on anomalous quartic gauge couplings

TL;DR

This study searches for exclusive W+W- production via photon-photon interactions in proton-proton collisions at 7 TeV, finding results consistent with the Standard Model and setting limits on anomalous quartic gauge couplings.

Contribution

It provides the first experimental constraints on anomalous quartic gauge couplings using exclusive W+W- production at the LHC.

Findings

Observed 2 events consistent with SM expectations

Set upper limits on anomalous quartic gauge couplings

No excess events at high transverse momentum

Abstract

A search for exclusive or quasi-exclusive W(+)W(-) production by photon-photon interactions, pp to p(*)W(+)W(-)p(*), at sqrt(s) = 7 TeV is reported using data collected by the CMS detector with an integrated luminosity of 5.05 inverse femtobarns. Events are selected by requiring a mu(+/-)e(-/+) vertex with no additional associated charged tracks and dilepton transverse momentum pt(mu(+/-)e(-/+)) > 30 GeV. Two events passing all selection requirements are observed in the data, compared to a standard model expectation of 2.2 +/- 0.4 signal events with 0.84 +/- 0.15 background. The tail of the dilepton pt distribution is studied for deviations from the standard model. No events are observed with pt > 100 GeV. Model-independent upper limits are computed and compared to predictions involving anomalous quartic gauge couplings. The limits on the parameters a[W,(0,C)]/Lambda^2 with a dipole form factor and an energy cutoff Lambda(cutoff) = 500 GeV are of the order of 10E-4.