Evidence ofWγγProduction inppCollisions ats=8  TeV

Abstract

This Letter reports evidence of triple gauge boson production pp → WðlνÞγγ þ X, which is accessible for the first time with the 8 TeV LHC data set. The fiducial cross section for this process is measured in a data sample corresponding to an integrated luminosity of 20.3 fb −1 , collected by the ATLAS detector in 2012. Events are selected using the W boson decay to eν or μν as well as requiring two isolated photons. The measured cross section is used to set limits on anomalous quartic gauge couplings in the high diphoton mass region.

Direct photon production and PDF fits reloaded

“…In addition to their relevance for PDF fits, photon production at the LHC is of great interest in searches for new physics beyond the standard model (BSM). For instance, recent searches for BSM physics with photons in the final state from ATLAS and CMS include searches for new particles by looking for high-mass resonances [25][26][27], anomalous couplings [28][29][30][31], and by measuring missing E T distributions [32][33][34][35]. These searches rely on a good understanding of the QCD background for photon production.…”

NLO QCD+EW corrections to diphoton production in association with a vector boson

“…where r γ denotes the angular separation between the photon and the parton, with 5) to define isolated photon candidates. These candidates are then ordered in transverse momentum.…”

“…In this context, we will representatively focus on W − bosons as we do not expect qualitatively different results for W + bosons. We define our fiducial phase space by following experimental setups [5]. First, we require the presence of exactly one charged lepton, dressed with all photons in a cone of size R = 0.1, with p T > 20 GeV and |η| < 2.5.…”

“…The class of processes that involve a pair of photons in association with another vector boson allows to measure deviations in triple and quartic gauge couplings and is therefore a particularly interesting class of processes. Consequently both ATLAS and CMS have measured these types of processes and derived constraints on anomalous gauge couplings [3][4][5][6].…”

Standard Model physics at the LHC

“…As illustrated in Figure 11(right), this distribution contains a host of interesting features: a resonance at the mass of the Z boson from the radiative decay Z → 4 , a resonance at the mass of the Higgs boson from its golden decay H → ZZ * → 4 , a threshold at twice the Z boson mass for the production of two onshell Z bosons, and finally a negative interference of gluon-induced ZZ-production diagrams with and without the Higgs boson, important especially above m 4 > 2m top , which is also sensitive to the width of the Higgs boson [99]. In contrast to the measurements of di-boson final states, which is entering the precision phase, the searches for tri-boson processes will require more luminosity, with the exception of the W γγ and Zγγ final states, for which evidence and observations have been reported, respectively [100,101,102].…”