On New Physics Contributions to the Higgs Decay to $Z\gamma$

TL;DR

This paper investigates the possibility of large enhancements in Higgs to Z gamma decay rates from new physics models, finding such enhancements require complex multiplet structures and interference effects, with potential detection via four-lepton decay measurements at future colliders.

Contribution

It demonstrates that simple models cannot produce large enhancements in Higgs to Z gamma decay, and identifies complex multiplet models where such effects are possible, highlighting experimental detection strategies.

Findings

Large enhancements require multiple electroweak multiplets.

Simple models like MSSM cannot produce >100% enhancement.

Future colliders may detect these effects through four-lepton decay channels.

Abstract

We explore models of new physics that can give rise to large (100% or more) enhancements to the rate of Higgs decay to $Z\gamma$ while still being consistent with other measurements. We show that this is impossible in simple models with one additional multiplet and also in well motivated models such as the MSSM and folded SUSY. We do find models with several multiplets that carry electroweak charge where such an enhancement is possible, but they require destructive interference effects. We also show that kinematic measurements in Higgs decay to four leptons can be sensitive to such models. Finally we explore the sensitivity of four lepton measurements to supersymmetric models and find that while the measurement is difficult with the high luminosity LHC, it may be possible with a future high energy hadron collider.