  A search for new physics in energetic, high-multiplicity final states has
been performed using proton-proton collision data collected with the CMS
detector at a center-of-mass energy of 13 TeV and corresponding to an
integrated luminosity of 2.3 inverse femtobarns. The standard model background,
dominated by multijet production, is determined exclusively from control
regions in data. No statistically significant excess of events is observed.
Model-independent limits on the product of the cross section and the acceptance
of a new physics signal in these final states are set and further interpreted
in terms of limits on the production of black holes. Semiclassical black holes
and string balls with masses as high as 9.5 TeV, and quantum black holes with
masses as high as 9.0 TeV are excluded by this search in the context of models
with extra dimensions, thus significantly extending limits set at a
center-of-mass energy of 8 TeV with the LHC Run 1 data.
