Search for dijet resonances in events with three jets from proton-proton collisions at $\sqrt{s}=13~\mathrm{TeV}$

A search for a narrow resonance, with a mass between 350 and 700 GeV and decaying into a pair of jets, is performed in proton-proton collisions with at least three jets in the final state. The data sample corresponds to an integrated luminosity of $18.3 ~\mathrm{fb}^{-1}$ collected at $\sqrt{s}=13~\mathrm{TeV}$ with the CMS detector. Data are collected with a technique known as "data scouting", in which the events are reconstructed, selected, and recorded at a high rate in a compact form by the high-level trigger. The three-jet final state provides sensitivity to lower values of the dijet mass than in previous searches using the data scouting technique. The spectrum of the dijet invariant mass, from the two jets with largest transverse momenta in the event, is searched for a bump arising from a dijet resonance. No significant excess is found and $95\%$ confidence level upper limits are presented on the production cross section of narrow resonances. The corresponding upper limits on the coupling, of a vector particle interacting only with quarks, is between 0.10 and 0.15 depending on the resonance mass.