Effects of Higgs sector CP violation in top-quark pair production at the LHC

TL;DR

This paper investigates how CP violation in the Higgs sector could be detected through specific asymmetries in top-quark pair production at the LHC, considering backgrounds and decay channels.

Contribution

It introduces new CP-sensitive observables in top-quark pair decays that can reveal Higgs sector CP violation at the LHC.

Findings

CP observables can signal Higgs CP violation with sufficient luminosity

Significant asymmetries are achievable for Higgs masses above 300 GeV

Methodology accounts for large top-antitop background

Abstract

A striking manifestation of CP violation in the electroweak symmetry breaking sector would be the existence of neutral Higgs boson(s) with undefined CP parity. We analyse signatures of such a boson, with a mass of about 300 GeV or larger, produced in high energy proton-proton collisions at LHC energies in its top-quark antitop-quark decay channel. The large irreducible $t\bar t$ background is taken into account. We propose, both for the dilepton and the lepton + jets decay channels of $t\bar t$, several correlations and asymmetries with which (Higgs sector) CP violation can be traced. We show that for judiciously chosen cuts on the $t\bar t$ invariant mass these CP observables yield, for an LHC integrated luminosity of 100 $\rm{fb}^{-1}$, statistically significant signals for a range of Higgs boson masses and Yukawa couplings.