Polarization effects in the Higgs boson decay to gamma Z and test of CP and CPT symmetries

TL;DR

This paper investigates polarization effects in Higgs boson decays to gamma gamma and gamma Z, proposing methods to test CP and CPT symmetries through polarization measurements and their deviations from the Standard Model.

Contribution

It introduces a framework using effective Lagrangian to analyze polarization parameters in Higgs decays, linking them to CP and CPT violation tests.

Findings

Nonzero photon circular polarization indicates CP-odd contributions.

Measurement of polarization parameters can reveal deviations from the Standard Model.

Circular polarization relates to fermion asymmetry in decay processes.

Abstract

Polarization characteristics of gamma gamma and gamma Z states in the Higgs boson decays h -> gamma gamma and h -> gamma Z are discussed. Based on effective Lagrangian, describing h gamma gamma and h gamma Z interactions with CP-even and CP-odd parts, we calculate polarization parameters xi_1, xi_2, xi_3. A nonzero value of the photon circular polarization, defined by parameter xi_2, arises due to presence of both parts in effective Lagrangian and its non-Hermiticity. The circular polarization is proportional to the forward-backward asymmetry of fermions in the decay h -> gamma Z -> gamma f bar{f}. Measurement of this observable would allow one to search for deviation from the standard model and possible violation of CPT symmetry. We discuss also a possibility to measure parameters xi_1, xi_3, describing correlation of linear polarizations of photon and Z boson, in the decay h -> gamma* Z -> l+ l- Z via distribution over the azimuthal angle between the decay planes of gamma* -> l+ l- and Z -> f bar{f}. Deviation of the measured value of xi_1 from zero will indicate CP violation in the Higgs sector.