Implications of CP-violating Top-Higgs Couplings at LHC and Higgs Factories

TL;DR

This paper constrains CP-violating top-Higgs couplings using LHC data, explores their effects on Higgs production processes at colliders, and assesses future measurement sensitivities to these couplings.

Contribution

It provides the most stringent bounds on CP-violating top-Higgs couplings from current data and analyzes their impact on various Higgs production processes at colliders.

Findings

Current bounds restrict CP-odd component |C^p_t|< 0.37

Higgs production cross sections can be significantly enhanced

Future measurements can further constrain CP-violating couplings

Abstract

We utilise the LHC Run-1 and -2 Higgs data to constrain the CP-violating top-Higgs couplings. In order to satisfy the current full Higgs data sets at $2\sigma$ level, the CP-odd component $C^p_t$ and the CP-even component $C^s_t$ have to be within the ranges $|C^p_t|< 0.37$ and $0.85 <C^s_t< 1.20$, respectively, which is stronger than the LHC Run-1 bound $|C^p_t|< 0.54$ and $0.68 <C^s_t< 1.20$. With the new bound, we explore the impact on the CP-violating top-Higgs couplings in the Higgs production processes $pp \to t\bar{t}h, thj, hh$ at 13 TeV LHC, and $e^+e^- \to hZ, h\gamma$ at future 240 GeV Higgs factories. We find that the cross sections of $pp \to t\bar{t}h$, $pp \to thj$, $pp \to hh$, $e^+e^- \to hZ$ and $e^+e^- \to h\gamma$ can be enhanced up to 1.41, 1.18, 2.20, 1.001 and 1.09 times as large as the SM predictions, respectively. The future precision measurement of the process $e^+e^- \to h\gamma$ with an accuracy of 5\% will be able to constrain $|C^p_t|<0.19$ at most at a 240 GeV $e^+e^-$ Higgs factory.