Search for light vector resonances decaying to a quark pair produced in association with a jet in proton-proton collisions at $\sqrt{s}=13~\mathrm{TeV}$

A search for narrow vector resonances decaying to a quark-antiquark pair is presented. The search is based on events collected in $\sqrt{s}=13~\mathrm{TeV}$ proton-proton collisions with the CMS detector at the LHC. The data sample, collected in 2016, corresponds to an integrated luminosity of $35.9~\mathrm{fb}^{-1}$. The hypothetical resonance is produced with sufficiently high transverse momentum that the decay products of the resonance are merged into a single jet. The resulting experimental signature is a single massive jet with two-prong substructure produced in association with a jet from initial-state radiation. Signal is identified as an enhancement over background processes in the distribution of the invariant mass of the jet. No evidence for such resonance is observed within the targeted mass range from $50-300~\mathrm{GeV}$. Upper limits at a $95\%$ confidence level are set on the production cross-section of leptophobic vector resonances. Results are presented in a mass-coupling phase space and are the most sensitive to date, extending previous limits below $100~\mathrm{GeV}$. The limits also constrain simplified models of dark matter, with a leptophobic mediator interacting between quarks and dark matter particles through a vector or axial-vector current.