  A search is presented for extra spatial dimensions, quantum black holes, and
quark contact interactions in measurements of dijet angular distributions in
proton-proton collisions at sqrt(s) = 13 TeV. The data were collected with the
CMS detector at the LHC and correspond to an integrated luminosity of 2.6
inverse femtobarns. The distributions are found to be in agreement with
predictions from perturbative quantum chromodynamics that include electroweak
corrections. Limits for different contact interaction models are obtained in a
benchmark model, valid to next-to-leading order in QCD, in which only
left-handed quarks participate, quark contact interactions are excluded up to a
scale of 11.5 or 14.7 TeV for destructive or constructive interference,
respectively. The production of quantum black holes is excluded for masses
below 7.8 or 5.3 TeV, depending on the model. The lower limits for the scales
of virtual graviton exchange in the Arkani-Hamed--Dimopoulos--Dvali model of
extra spatial dimensions are in the range 7.9-11.2 TeV, and are the most
stringent set of limits available.
