  A search for the resonant production of high-mass photon pairs is presented.
The analysis is based on samples of proton-proton collision data collected by
the CMS experiment at center-of-mass energies of 8 and 13 TeV, corresponding to
integrated luminosities of 19.7 and 3.3 inverse femtobarns, respectively. The
search focuses on spin-0 and spin-2 resonances with masses between 0.5 and 4
TeV and with widths, relative to the mass, between 1.4E-4 and 5.6E-2. Limits
are set on scalar resonances produced through gluon-gluon fusion, and on
Randall-Sundrum gravitons. A modest excess of events compatible with a narrow
resonance with a mass of about 750 GeV is observed. The local significance of
the excess is approximately 3.4 standard deviations. The significance is
reduced to 1.6 standard deviations once the effect of searching under multiple
signal hypotheses is considered. More data are required to determine the origin
of this excess.
