Search for pair production of heavy resonances in final states with a photon and large-radius jets in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A search for the pair production of heavy spin-1/2 or spin-3/2 resonances (𝑡*) in proton-proton collisions at √𝑠 =13  TeV is presented. Data collected with the CMS detector at the CERN LHC from 2016 to 2018 corresponding to an integrated luminosity of 138  fb$^{−1}$ are used. The analysis targets benchmark signal scenarios where one 𝑡* decays into a top quark (𝑡) and a photon (𝛾), and the other into a 𝑡 quark and a gluon (𝑔), i.e., 𝑝⁢𝑝→𝑡*⁢$\overline{𝑡}$*→𝑡⁢𝑡⁢𝛾⁢𝑔. All-hadronic final states from the 𝑡 pair decay chain are selected using jet substructure techniques. The signal is probed as a function of the 𝑡* candidate mass, which is reconstructed using the photon and a top quark candidate jet. No significant deviation from the background-only hypothesis is found. Observed (expected) upper limits on the signal cross section at 95% confidence level are set, excluding masses of spin-1/2 𝑡* particles below 930 (930) GeV and spin-3/2 𝑡* particles below 1330 (1390) GeV. This analysis marks the first search for heavy resonances in the 𝑡⁢$\overline{𝑡}$⁢𝛾⁢𝑔 channel. Exploiting the high-energy photon to reduce the backgrounds, this search achieves sensitivity competitive with 𝑝⁢𝑝→𝑡*⁢$\overline{𝑡}$*→𝑡⁢$\overline{𝑡}$⁢𝑔⁡𝑔 searches for spin-1/2 𝑡* despite the small expected 𝑡* →𝑡⁢𝛾 branching fraction.