Probing Charm Yukawa Coupling through $ch$ Associated Production at the Hadron Colliders

TL;DR

This paper proposes a novel method to probe the charm Yukawa coupling at hadron colliders by analyzing associated production with the Higgs, utilizing interference effects and machine learning to improve sensitivity to the coupling's magnitude and CP phase.

Contribution

It introduces a new approach using interference in charm-Higgs production and machine learning to measure charm Yukawa coupling and CP phase at colliders.

Findings

Achieves bounds of -5.6 to 5.6 on  at HL-LHC

Achieves bounds of -1.51 to 1.62 on  at FCC

Provides sensitivity to CP phase  between 7b0 and 77b0 at HL-LHC

Abstract

At present, the study of the charm-quark Yukawa coupling at the Large Hadron Collider mainly focuses on the Higgs decay processes. Such signal suffers from overwhelming QCD background and derives its sensitivity primarily from the $Vh$ associated production channel. In addition, sensitivity to a possible CP phase in charm-quark Yukawa at the hadron collider is not discussed. We investigate the charm-Higgs associated production signal, that contains a potentially detectable interference term between $cch$ Yukawa coupling mediated diagrams and $ggh$ coupling mediated diagram. Such interference term is sensitive to the relative CP phase between contributing diagrams. High dimensional kinematic information are exploited by machine learning techniques to separate the different contribution, and sensitivity on the coupling is derived. Assuming a real $\kappa_c$ modification framework, 1$\sigma$ bound of $-5.6 < \kappa_c < 5.6$ (HL-LHC) and $-1.51 < \kappa_c < 1.62$ (FCC) are achieved. When allowing for CP-phase in the charm Yukawa, a combined 1$\sigma$ bound of $0.32<|\kappa_c|<1.69$, $-77^\circ < \alpha < 77^\circ$ (HL-LHC) and $0.70<|\kappa_c|<1.29$, $-55^\circ < \alpha < 55^\circ$ (FCC) can be achieved on the magnitude and CP phase of the coupling respectively.