Search for heavy H$\gamma$ and Z$\gamma$ resonances with a bottom quark-antiquark pair in the final state in proton-proton collisions at $\sqrt{s}$ = 13 TeV

TL;DR

This paper reports a search for heavy resonances decaying into Higgs or Z bosons plus a photon, using CMS data at 13 TeV, employing advanced jet classification techniques, and sets new upper limits on such processes.

Contribution

Introduces a transformer-based jet classification algorithm to identify boosted H/Z to b-bbar decays in resonance searches at the LHC.

Findings

No significant excess observed over the standard model.

Sets the most stringent upper limits to date on cross section times branching fraction.

Limits are below 0.1 fb for Hγ and 0.3 fb for Zγ resonances.

Abstract

A search for heavy resonances decaying into a Higgs boson (H) or a Z boson and a photon ($\gamma$), with the H or Z bosons decaying to a bottom quark-antiquark pair ($\mathrm{b\bar{b}}$) is presented. The analysis is performed using proton-proton collision data at $\sqrt{s}$ = 13 TeV collected by the CMS experiment at the CERN Large Hadron Collider, corresponding to an integrated luminosity of 138 fb$^{-1}$. The analyzed events contain a photon and a massive large-radius jet originating from a Lorentz-boosted $\mathrm{b\bar{b}}$ system. An advanced transformer-based algorithm classifies jets according to their substructure and quark flavors, forming a tagger that identifies jets as candidates from H/Z $\to$ $\mathrm{b\bar{b}}$ decays. A set of parametric functions is used to fit the photon-jet invariant mass spectrum and to extract potential signals. No significant excess is observed above the standard model expectations. The results set upper limits at 95% confidence level on the product of the cross section and the branching fraction for spin-1 H$\gamma$ resonances and spin-0 Z$\gamma$ resonances, below 0.1 and 0.3 fb, respectively, representing the most stringent limits to date.