Search of a Vector-Like Quark $T^\prime\rightarrow$ tH in the di-photon final state

A search for the production of a Vector-Like Quark, $T^\prime$ is presented. The search is based on proton-proton collision events collected at $13~\mathrm{TeV}$ by the CMS detector at the CERN LHC. The data sample corresponds to an integrated luminonsity of $138~\mathrm{fb}^{-1}$, collected between 2016 and 2018. The search looks specifically for the production of a $T^\prime$ quark which then decays to a top quark and a Higgs boson ($T^\prime\rightarrow tH$); with the Higgs boson subsequently decaying into a pair of photons ($H\rightarrow \gamma \gamma$). The top quark can decay either hadronically ($t\rightarrow bq\bar{q}$) or leptonically ($t \rightarrow bl\nu$). This search presents an upper limit on the $T^\prime$ production cross section for the mass range $600-1200~\mathrm{GeV}$. No significant excess over the standard model background is observed, accordingly $T'$ masses up to $730~\mathrm{GeV}$ are excluded at $95\%$ confidence level. This search is the first to use the reconstruction of the $H\rightarrow \gamma \gamma$ invariant mass, leveraging an experimental resolution of $1-2 \%$. This technique leads to an increased sensitivity to $T^\prime$ mass values up to $1~\mathrm{TeV}$ with respect to the previous searches.