Search for Narrow Resonances using the Dijet Mass Spectrum with 42 pb^-1 of pp Collisions at $\sqrt{s}=13$ TeV

A search for narrow dijet resonances in proton-proton (pp) collisions at $\sqrt{s}=13$ TeV is presented. The dijet mass distribution of the two leading jets is measured with the CMS detector. The data used correspond to an integrated luminosity of 42 pb$^{-1}$ from Run 2 of the LHC. The pseudorapidity separation of the two jets is required to satisfy $|\Delta\eta_{\text{jj}}|<1.3$ with each jet inside the region $|\eta| < 2.5$. The highest observed dijet mass is 5.4 TeV. The spectrum is well described by a smooth parameterization and no significant evidence for new particle production is observed. Upper limits at the $95\%$ confidence level are set on the resonance cross section. By comparing these generic limits with theoretical predictions for the cross section of several models of new particles, lower limits are set on the mass of string resonances, excited quarks, axigluons, colorons, scalar diquarks and color octet scalars. For resonance masses greater than 5 TeV this search is expected to be more sensitive than those in Run 1 of the LHC at $\sqrt{s}=8$ TeV. A lower mass limit of 5.1 TeV is set for string resonances which extends previous exclusions from Run 1.