Searches for dijet resonances in pp collisions at $\sqrt{s}=13~\mathrm{TeV}$ using the 2016 and 2017 datasets

Searches are presented for resonances decaying to dijet final states in proton-proton collisions at $\sqrt{s}=13~\mathrm{TeV}$. A high-mass search, for resonances with mass above 1.8 TeV, is performed using dijets reconstructed from data corresponding to an integrated luminosity of $77.8~\mathrm{fb}^{-1}$. The main QCD background is predicted both by fitting the data with an empirical functional form, and with a data-driven method via a $|\Delta\eta|$ sideband. The dijet mass spectrum is well described by both methods and no significant evidence for the production of new particles is observed. Upper limits at $95\%$ confidence level are reported on the production cross section for narrow resonances with masses above 1.8 TeV extending previous searches. Limits are placed on the mass of dijet resonances within various models of new physics.