Search for narrow trijet resonances in proton-proton collisions at $\sqrt{s}= 13\,$TeV

A search for narrow hadronic resonances decaying to three resolved jets is presented. The search uses $138\,\text{fb}^{-1}$ of proton-proton collision data with a collision center of mass energy of $13\,\text{TeV}$, collected by the CMS detector at the CERN LHC. The three-jet invariant mass spectrum is scrutinized for localized excesses compatible with new resonances with masses in the range of $1.75$--$9.00\,\text{TeV}$. The background from standard model processes is estimated by fitting the three-jet invariant mass spectrum with empirical functions, following techniques commonly used in dijet resonance searches. No significant deviations from the background expectations are observed. The results are interpreted in the context of several models predicting three-jet resonances, including a new right-handed boson $\mathrm{Z}_{R}$ decaying to three gluons, a Kaluza-Klein gluon decaying via an intermediate radion to three gluons, and an excited quark decaying via a vector boson to three quarks.