Measuring properties of a Heavy Higgs boson in the $H\to ZZ \to 4\ell$ decay

TL;DR

This paper develops a comprehensive method to analyze the angular distributions of decay products from a heavy Higgs boson decaying into four leptons, enabling detailed study of its CP properties and couplings.

Contribution

It introduces a general framework using helicity amplitudes to fully determine Higgs-Z couplings from angular observables in the four-lepton decay channel.

Findings

Nine angular observables can determine all Higgs-Z couplings.

For 1000 events, couplings can be measured with 12-20% uncertainty.

Method applicable to Higgs mass around 260 GeV below the top pair threshold.

Abstract

In many extensions of the standard model, there exist a few extra Higgs bosons. Suppose a heavy neutral Higgs boson H is discovered at the LHC, one could then investigate CP and CPT~ properties of its couplings to a pair of $Z$ bosons through $H \to ZZ \to 4\ell$. We use the helicity-amplitude method to write down the most general form for the angular distributions of the four final-state leptons, which can cover the case of CP-even, -odd, and -mixed state for the Higgs boson. We figure out there are 9 types of angular observables and all the $H$ couplings to $Z$ bosons can be fully determined by exploiting them. A Higgs-boson mass of 260 GeV below the $t\bar t$ threshold is illustrated with full details. With a total of $10^3$ events of $H \to ZZ \to 4\ell$, one can determine the couplings up to 12-20\% uncertainties.