Search for flavor-changing neutral current interactions of the top quark and Higgs boson in final states with two photons in proton-proton collisions at $\sqrt{s} =$ 13 TeV

TL;DR

This study searches for flavor-changing neutral current interactions between top quarks and Higgs bosons in proton-proton collisions at 13 TeV, setting the most stringent upper limits to date on their decay probabilities.

Contribution

It provides the first limits on top-Higgs flavor-changing interactions in final states with two photons at 13 TeV, improving constraints on new physics models.

Findings

No significant excess observed above background.

Upper limits on branching fractions are set at 0.019% for t→Hu and 0.073% for t→Hc.

Results are the most restrictive to date.

Abstract

Proton-proton interactions resulting in final states with two photons are studied in a search for the signature of flavor-changing neutral current interactions of top quarks (t) and Higgs bosons (H). The analysis is based on data collected at a center-of-mass energy of 13 TeV with the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb$^{-1}$. No significant excess above the background prediction is observed. Upper limits on the branching fractions ($\mathcal{B}$) of the top quark decaying to a Higgs boson and an up (u) or charm quark (c) are derived through a binned fit to the diphoton invariant mass spectrum. The observed (expected) 95% confidence level upper limits are found to be 0.019 (0.031)% for $\mathcal B$(t $\to$ Hu) and 0.073 (0.051)% for $\mathcal{B}$(t $\to$ Hc). These are the strictest upper limits yet determined.