  A search for resonances in events with the $\gamma$+jet final state has been
performed using proton-proton collision data collected at $\sqrt{s}$ = 13 TeV
by the CMS experiment at the LHC. The total data analyzed correspond to an
integrated luminosity of 138 fb$^{-1}$. Models of excited quarks and quantum
black holes are considered. Using a wide-jet reconstruction for the candidate
jet, the $\gamma$+jet invariant mass spectrum measured in data is examined for
the presence of resonances over the standard model continuum background. The
background is estimated by fitting the mass distribution with a functional
form. The data exhibit no statistically significant deviations from the
expected standard model background. Exclusion limits at 95% confidence level on
the resonance mass and other parameters are set. Excited light-flavor quarks
(excited bottom quarks) are excluded up to a mass of 6.0 (3.8) TeV. Quantum
black hole production is excluded for masses up to 7.5 (5.2) TeV in the
Arkani-Hamed-Dimopoulos-Dvali (Randall-Sundrum) model. These lower mass bounds
are the most stringent to date among those obtained in the $\gamma$+jet final
state.
