Study of exclusive two-photon production of W+W- pairs in pp collisions at 7 TeV, and constraints on anomalous quartic couplings in CMS

A search for exclusive W + W − production by photon - photon fusion, p p → p W + W − p , at √ s = 7 TeV is reported using data collected by the CMS detector wit h an integrated luminosity of 5 fb − 1 . Events are selected by requiring a μ ± e ∓ vertex with no additional associated charged tra cks and dilepton transverse mo mentum p T (μ ± e ∓ ) > 30 GeV. Two events passing all selection requirements are observed in the data, co mpared to a standard model expectation of 2.2 ± 0.4 signal events with 0.84 ± 0.15 background. The tail of the dilepton p T distribution is studied for deviations from the standard model. No events are observed with p T > 100 GeV. Model - independent upper lim its are computed and compared to predictions involving anomalous quartic gauge couplings. The limits on the parameters a W 0,C / Λ 2 with a dipole form factor and an energy cutoff Λ cutoff = 500 GeV are of the order of 10 − 4 GeV - 2 .