Indirect mathcal{CP} probes of the Higgs-top-quark interaction: current LHC constraints and future opportunities

Henning Bahl,Georg Weiglein,Tim Stefaniak,Judith Katzy,Philip Bechtle,Krisztian Peters,Sven Heinemeyer,Matthias Saimpert,Tobias Klingl

doi:10.1007/jhep11(2020)127

Abstract

The mathcal{CP} structure of the Higgs boson in its coupling to the particles of the Standard Model is amongst the most important Higgs boson properties which have not yet been constrained with high precision. In this study, all relevant inclusive and differential Higgs boson measurements from the ATLAS and CMS experiments are used to constrain the mathcal{CP} -nature of the top-Yukawa interaction. The model dependence of the constraints is studied by successively allowing for new physics contributions to the couplings of the Higgs boson to massive vector bosons, to photons, and to gluons. In the most general case, we find that the current data still permits a significant mathcal{CP} -odd component in the top-Yukawa coupling. Furthermore, we explore the prospects to further constrain the mathcal{CP} properties of this coupling with future LHC data by determining tH production rates independently from possible accompanying variations of the toverline{t}H rate. This is achieved via a careful selection of discriminating observables. At the HL-LHC, we find that evidence for tH production at the Standard Model rate can be achieved in the Higgs to diphoton decay channel alone.

Highlights

In 2012 the ATLAS and CMS collaborations have discovered a new particle that — within current theoretical and experimental uncertainties — is consistent with the predictions of a Standard-Model (SM) Higgs boson at a mass of ∼ 125 GeV [1, 2]
We evaluate the feasibility of an analysis for the separate measurement of tH and that jet in tH (ttH) + tW H production that is designed to remain independent of the CP-character of the top-Yukawa coupling
Less than two events in total are expected at the 300 fb−1 LHC in the 2-lepton category in all four CP scenarios, indicating that additional data from the high-luminosity LHC (HL-LHC) is required to successfully implement the strategy being followed in this work

Summary

Introduction

In 2012 the ATLAS and CMS collaborations have discovered a new particle that — within current theoretical and experimental uncertainties — is consistent with the predictions of a Standard-Model (SM) Higgs boson at a mass of ∼ 125 GeV [1, 2]. The measurements of Higgs-boson couplings, which are known experimentally to a precision of roughly ∼ 20%, leave room for Beyond Standard-Model (BSM) interpretations. One of the main tasks of the LHC Run 3 and the high-luminosity LHC (HL-LHC) will be to determine the Higgs-boson coupling structures and quantum numbers with highest precision. This experimental program has a direct link to cosmology. The main idea of this work is to investigate to which extent CP violation beyond the CKM matrix can be present in the interactions of the detected Higgs boson. We investigate here the interaction between the Higgs boson and the top quark

Results

Discussion

Conclusion