CP violating anomalous couplings in $W\gamma$ and $Z\gamma$ production at the LHC

TL;DR

This paper investigates the potential for the LHC to set limits on CP-violating anomalous couplings in $W ext{ } ext{and} ext{ }Z ext{ } ext{production}$ processes, providing estimates of achievable bounds at 14 TeV.

Contribution

It offers the first estimates of LHC sensitivity to specific CP-violating anomalous couplings in $W ext{ } ext{and} ext{ }Z ext{ } ext{production}$, extending previous bounds on CP-conserving couplings.

Findings

$pp \to W\gamma$ at 14 TeV can constrain $|\kappa\tilde{\gamma}| < 0.05$ with 10 fb$^{-1}$

$pp \to Z\gamma$ can limit $|h^1_{\gamma,Z}|$ to approximately 20 and 40 respectively

Current limits cannot distinguish CP-violating effects from other contributions due to lack of CP-odd observables

Abstract

The ATLAS and CMS collaborations have recently published new limits on CP conserving anomalous couplings from the $W\gamma$ and $Z\gamma$ production processes. We study the corresponding limits that can be placed on the CP violating anomalous couplings $\kappa_tilde_\gamma$ and $h^1_{\gamma, Z}$ at the LHC. We find that the process $pp --> W\gamma$ at 14 TeV can place the 95% CL limit $|\kappa_tilde_\gamma| <~ 0.05$ with 10 fb^{-1} which is comparable to the existing LHC bound on the CP conserving anomalous couplings $\kappa_\gamma$. Similarly, the process $pp --> Z\gamma$ can place the 95% CL limits $|h^1_\gamma| <~ 20$ and $|h^1_Z| <~ 40$ respectively. None of these limits is derived from a truly CP-odd observable so that it is not possible to separate the effects of the CP violating anomalous couplings from the rest.