How to pin down the CP quantum numbers of a Higgs boson in its tau decays at the LHC

TL;DR

This paper proposes a method to determine the CP quantum numbers of a neutral Higgs boson at the LHC by analyzing tau decay distributions, showing it is feasible with sufficient data after high-luminosity runs.

Contribution

It applies an angle-based analysis method to tau decays to distinguish CP properties of the Higgs boson at the LHC, including selection cuts to improve discrimination.

Findings

Discriminating power is significantly enhanced by appropriate selection cuts.

Feasibility of distinguishing CP-even and CP-odd Higgs bosons with enough event data.

Analysis remains effective for various tau decay final states.

Abstract

We investigate how the CP quantum numbers of a neutral Higgs boson or spin-zero resonance, produced at the CERN Large Hadron Collider, can be determined in its tau-pair decay mode. We use a method developed in an earlier paper based on the distributions of two angles and apply it to the major 1-prong tau decays. We show for the resulting dilepton, lepton-pion, and two-pion final states that appropriate selection cuts significantly enhance the discriminating power of these observables. From our analysis we conclude that, provided a Higgs boson will be found at the LHC, it appears feasible to collect the event numbers needed to discriminate between a CP-even and -odd Higgs boson and/or between Higgs boson(s) with CP-conserving and CP-violating couplings after several years of high-luminosity runs.