A search for narrow low-mass resonances decaying to quark-antiquark pairs is presented. The search is based on proton-proton collision events collected at 13 TeV by the CMS detector at the CERN LHC. The data sample corresponds to an integrated luminosity of 35.9 fb(-1), recorded in 2016. The search considers the case where the resonance has high transverse momentum due to initial-state radiation of a hard photon. To study this process, the decay products of the resonance are reconstructed as a single large-radius jet with two-pronged substructure. The signal would be identified as a localized excess in the jet invariant mass spectrum. No evidence for such a resonance is observed in the mass range 10 to 125 GeV. Upper limits at the 95% confidence level are set on the coupling strength of resonances decaying to quark pairs. The results obtained with this photon trigger strategy provide the first direct constraints on quark-antiquark resonance masses below 50 GeV obtained at a hadron collider.

Search for Low-Mass Quark-Antiquark Resonances Produced in Association with a Photon at root s=13 TeV

Azzi, P.;Boletti, A.;Bragagnolo, A.;Carlin, R.;Checchia, P.;Gasparini, F.;Gasparini, U.;Gozzelino, A.;Hoh, S. Y.;Lacaprara, S.;Lujan, P.;Margoni, M.;Meneguzzo, A. T.;Pazzini, J.;Pozzobon, N.;Ronchese, P.;Rossin, R.;Simonetto, F.;Torassa, E.;Zanetti, M.;Zotto, P.;Zumerle, G.;Triossi, A.;Tosi, M.;Zucchetta, A.;