Search for flavor-changing neutral current interactions of the top quark and the Higgs boson in the diphoton decay channel in proton-proton collisions at $\sqrt{s}=13~\mathrm{TeV}$

Proton-proton interactions resulting in the prodution of a Higgs boson with subsequent decay into two photons are studied in a search for the signature of flavor-changing neutral current interactions of top quarks and Higgs bosons. The analysis is based on data collected at a center-of-mass energy $\sqrt{s}=13~\mathrm{TeV}$ by the CMS detector at the LHC, corresponding to an integrated luminosity of $137~\mathrm{fb}^{-1}$. Multivariate machine learning techniques are used to separate signal and standard model background processes. No significant excess above the background prediction is observed, and upper limits on the $\mathrm{t} \to \mathrm{Hq}$ branching fractions are derived through a binned fit to the diphoton invariant mass spectrum. The observed (expected) $95\%$ confidence level upper limits are found to be $1.9 \times 10^{-4}$ ($3.1 \times 10^{-4}$) for $\mathcal B(\mathrm{t} \to \mathrm{Hu})$ and $7.3 \times 10^{-4}$ ($5.1 \times 10^{-4}$) for $\mathcal B(\mathrm{t} \to \mathrm{Hc})$.