Theoretical Basis of Higgs-Spin Analysis in $H \to \gamma\gamma$ and $Z\gamma$ Decays

TL;DR

This paper explores the theoretical foundations of using Higgs boson radiative decays to determine its spin, analyzing angular distributions to distinguish between spin-zero and higher spin hypotheses.

Contribution

It provides a systematic helicity analysis framework for interpreting angular distributions in Higgs radiative decays, aiding spin determination.

Findings

Angular distributions differ significantly between spin-zero and higher spins.

Radiative decay channels offer complementary information for Higgs spin analysis.

Theoretical basis established for future experimental spin measurements.

Abstract

We chart the theoretical basis of radiative decays of the Higgs boson, $H \to \gamma\gamma$ and $Z\gamma$, for measuring the spin of the Higgs particle. These decay channels are complementary to other rare modes such as real/virtual $Z$-boson pair-decays. In systematic helicity analyses the angular distribution for zero-spin is confronted with hypothetical spin-$2^\pm$ and higher assignments to quantify the sensitivity.