# Charm-quark Yukawa Coupling in $h\rightarrow c\bar{c}\gamma$ at LHC

## TL;DR

This paper explores the potential to measure the charm-quark Yukawa coupling at the LHC through the rare decay $h
ightarrow car{c} ext{ } ext{ extgamma}$, using advanced triggering and machine learning techniques to overcome background challenges.

## Contribution

It proposes a novel method to probe the charm Yukawa coupling via Higgs radiative decay, achieving a sensitivity of about 8 times the SM value at the HL-LHC.

## Key findings

- Potential to set a coupling limit of ~8 times the SM value at HL-LHC.
- Refined trigger strategy combined with machine learning improves signal detection.
- No significant improvement expected from higher energy colliders without detector upgrades.

## Abstract

It is extremely challenging to probe the charm-quark Yukawa coupling at hadron colliders primarily due to the large Standard Model (SM) background (including $h\to b\bar b$) and the lack of an effective trigger for the signal $h\to c\bar c$. We examine the feasibility of probing this coupling at the LHC via a Higgs radiative decay $h\rightarrow c\bar{c}\gamma$. The existence of an additional photon in the final state may help for the signal identification and background suppression. Adopting a refined triggering strategy and utilizing basic machine learning, we find that a coupling limit of about 8 times the SM value may be reached with $2\sigma$ sensitivity after the High Luminosity LHC (HL-LHC). Our result is comparable and complementary to other projections for direct and indirect probes of $h\to c\bar c$ at the HL-LHC. Without a significant change in detector capabilities, there would be no significant improvement for this search from higher energy hadron colliders.