A search for WWγ and WZγ triboson production and anomalous quartic gauge couplings at sqrt(s) = 8 and 13 TeV within the Compact Muon Solenoid

An analysis probing for the standard model production of three electroweak vector bosons, WVgamma with V = W or Z gauge boson, is presented. The W boson decays leptonically to an electron or muon, or their respective antiparticle, paired with the appropriate neutrino. The second boson V decays hadronically into two jets, and additionally a photon is required in the event. The data analyzed correspond to an integrated luminosity of 19.6 inv. fb. and 2.3 inv. fb. from proton-proton collisions at sqrt(s) = 8 TeV and 13 TeV, respectively, collected in 2012 and 2015 by the CMS detector at the Large Hadron Collider. The event selection criteria used in these analyses yields 322 and 46 observed events in data in 2012 and 2015, respectively, while the estimated background yield from theoretical predictions is 342.1 ± 22.2 and 54.3 ± 17.7. These observations are consistent with the standard model next-to-leading order QCD predictions. Given the limitation in statistics to measure the cross section for this production process, an upper limit of 3.4 times the standard model predictions is made at a 95% confidence level for WVgamma with photon p_T greater than 30 GeV and absolute pseudorapidity less than 1.44.

Physics beyond the standard model, such as anomalous couplings between the gauge bosons at the quartic vertex, may lead to enhancement in the number of WVgamma events produced within high energy collisions. Such enhancements can be observed in kinematic distributions, particularly in the higher energy regions. No evidence of anomalous WWgamma gamma and WWZgamma quartic gauge boson couplings is found, while 95% confidence level upper limits are obtained for various couplings.