# Probe CP violation in $H\to \gamma Z$ through forward-backward asymmetry

## TL;DR

This paper proposes using the forward-backward asymmetry of leptons in Higgs decay to gamma and Z bosons to detect CP violation in the $H o ext{gamma} Z$ coupling, accounting for interference effects.

## Contribution

It introduces a novel method to probe CP violation in the $H o ext{gamma} Z$ coupling via lepton asymmetry, considering interference with background processes.

## Key findings

- Non-zero $A_{FB}$ indicates CP violation.
- Interference effects cause $A_{FB}$ to change sign around Higgs mass.
- Integral over specific mass regions enhances $A_{FB}$ signal.

## Abstract

We suggest that the forward-backward asymmetry $(A_{FB})$ of the charged leptons in $gg\to H\to\gamma Z\to\gamma \ell^-\ell^+$ process could be used to probe the CP violating $H\gamma Z$ coupling when the interference from $gg\to\gamma Z\to\gamma \ell^-\ell^+$ process is included. With CP violation in $H\gamma Z$ coupling, the interference effect leads to a non-vanishing $A_{FB}$, which is also sensitive to the strong phase differences. The resonant and non-resonant strong phases together make $A_{FB}(\hat{s})$ change sign around Higgs mass $M_H$. For phenomenology study, we suggest the integral over one-side mass region below $M_H$ to magnify the $A_{FB}$ strength.