Discovering the $h\to Z \gamma$ Decay in $t \bar t$ Associated Production

TL;DR

This paper investigates the potential to observe the Higgs decay to Z gamma in association with top quark pairs at current and future colliders, aiming for discovery and precise property measurements.

Contribution

It provides a detailed analysis of the $t\bar t$-associated production channel for $h \to Z \gamma$, demonstrating its feasibility for discovery and precision measurements at the HL-LHC and future colliders.

Findings

Potential for a $\sim5\sigma$ discovery at HL-LHC

Extraction of $h Z \gamma$ coupling with $\sim15\%$ accuracy

Future colliders could measure Higgs properties at the few percent level

Abstract

We explore the prospects to discover the $h \to Z \gamma$ decay in $t\bar t$-associated production, featuring a signal-to-background ratio of ${\cal O}(1)$. Performing a detailed analysis of the semi-leptonic $t \bar t $-decay channel, we demonstrate that the production mode could lead to a $\sim5\,\sigma$ discovery at the high-luminosity LHC, while the effective $h Z \gamma$ coupling could be extracted with a $\sim15\,\%$ accuracy. Extending the analysis to potential future $pp$ colliders with 27 TeV and 100 TeV center-of-mass energies, we also show that the latter would allow precision measurements at the few percent level, rendering possible precise extractions of the spin and CP properties of the Higgs boson.