Search for excited quarks in the $\gamma +$jet final state in proton–proton collisions at $\sqrt s=8$ TeV

A search for excited quarks decaying into the γ+jet final state is presented. The analysis is based on data corresponding to an integrated luminosity of 19.7 fb$^{−1}$ collected by the CMS experiment in proton–proton collisions at $\sqrt{s}$ = 8 TeV at the LHC. Events with photons and jets with high transverse momenta are selected and the γ+jet invariant mass distribution is studied to search for a resonance peak. The 95% confidence level upper limits on the product of cross section and branching fraction are evaluated as a function of the excited quark mass. Limits on excited quarks are presented as a function of their mass and coupling strength; masses below 3.5 TeV are excluded at 95% confidence level for unit couplings to their standard model partners.