Evidence of $W\gamma \gamma$ Production in $pp$ Collisions at $\sqrt{s}=8\mathrm{TeV}$ and Limits on Anomalous Quartic Gauge Couplings with the ATLAS Detector

This Letter reports evidence of triple gauge boson production $pp\to W(\ell \nu )\gamma \gamma +X$, 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 $20.3{\mathrm{fb}}^{-1}$, collected by the ATLAS detector in 2012. Events are selected using the $W$ boson decay to $e\nu$ or $\mu \nu$ 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.

Figure 1

Diphoton invariant mass distribution in the electron (left) and muon (right) channels. The expected signal based on the sherpa prediction is shown. The hashed areas show the total systematic and statistical uncertainty on the background estimate.