Search for pair production of heavy resonances in photon plus large-radius jets final states in pp collisions at 13 TeV

We present a search for the pair production of heavy spin-3/2 or spin-1/2 resonances ($\mathrm{t}^{*}$) in proton-proton collisions at $\sqrt{s}=13~\mathrm{TeV}$. We use data collected by the CMS detector at the CERN LHC from 2016 to 2018, corresponding to an integrated luminosity of $138~\mathrm{fb}^{-1}$. The analysis targets signal scenarios where one $\mathrm{t}^{*}$ decays into a top quark (t) and a gluon (g), and the other into a t and a photon ($\gamma$), via the process $\mathrm{pp}\rightarrow\mathrm{t}^{*}\bar{\mathrm{t}}^{*}\rightarrow\mathrm{tg\bar{t}}\gamma$. All-hadronic final states from the t pair decay chain are selected using jet substructure techniques. The mass of the $\mathrm{t}^{*}$ candidate is reconstructed using the photon and a top-candidate jet, which is then used to probe the signal. No significant deviation from the background-only hypothesis is observed. Observed (expected) upper limits on the signal cross section at $95\%$ confidence level are set, excluding masses of spin-$\frac{1}{2}$ $\mathrm{t}^{*}$ particles below $940~(1000)~\mathrm{GeV}$ and spin-$\frac{3}{2}$ $\mathrm{t}^{*}$ particles below $1330~(1410)~\mathrm{GeV}$. This analysis marks the first search for heavy resonances in the $\mathrm{tg\bar{t}}\gamma$ final state. Exploiting the high-energy photon, which reduces background despite the small $\mathrm{t}^{*}\rightarrow\mathrm{t}\gamma$ branching ratio, this search achieves sensitivity comparable to $\mathrm{pp}\rightarrow\mathrm{t}^{*}\bar{\mathrm{t}}^{*}\rightarrow\mathrm{tg\bar{t}g}$ searches.