Quartic Gauge Couplings and the Radiation Zero in pp to l nu gamma gamma events at the LHC

TL;DR

This paper investigates pp to l nu gamma gamma events at the LHC to set limits on anomalous quartic gauge couplings and explores the Standard Model radiation zero feature, using simulations and likelihood analysis with 30fb-1 data.

Contribution

It introduces a method to constrain anomalous W W gamma gamma couplings and demonstrates the potential to observe the radiation zero in pp collisions at the LHC.

Findings

Limits on anomalous couplings are two orders of magnitude tighter than LEP.

The radiation zero feature can be observed in the difference of pseudo-rapidities.

Simulation results support the feasibility of these measurements at the LHC.

Abstract

We report a study of the process pp to l nu gamma gamma at CERN's Large Hadron Collider, using a leading order partonic-level event generator interfaced to the Pythia program for showering and hadronisation and a with a generic detector simulation. The process is sensitive to possible anomalous quartic gauge boson couplings of the form W W gamma gamma. It is shown how unitarity-safe limits may be placed on these anomalous couplings by applying a binned maximum likelihood fit to the distribution of the two-photon invariant mass, M(gamma gamma), below a cutoff of 1TeV. Assuming 30fb-1 of integrated luminosity, the expected limits are two orders of magnitude tighter than those available from LEP. It is also demonstrated how the Standard Model radiation zero feature of the qq to W gamma gamma process may be observed in the difference between the two-photon and charged lepton pseudo-rapidities.