  A search is presented for narrow resonances decaying to dijet final states in
proton-proton collisions at sqrt(s) = 13 TeV using data corresponding to an
integrated luminosity of 12.9 inverse femtobarns. The dijet mass spectrum is
well described by a smooth parameterization and no significant evidence for the
production of new particles is observed. Upper limits at 95% confidence level
are reported on the production cross section for narrow resonances with masses
above 0.6 TeV. In the context of specific models, the limits exclude string
resonances with masses below 7.4 TeV, scalar diquarks below 6.9 TeV, axigluons
and colorons below 5.5 TeV, excited quarks below 5.4 TeV, color-octet scalars
below 3.0 TeV, W' bosons below 2.7 TeV, Z' bosons below 2.1 TeV and between 2.3
and 2.6 TeV, and RS gravitons below 1.9 TeV. These extend previous limits in
the dijet channel. Vector and axial-vector mediators in a simplified model of
interactions between quarks and dark matter are excluded below 2.0 TeV. The
first limits in the dijet channel on dark matter mediators are presented as
functions of dark matter mass and are compared to the exclusions of dark matter
in direct detection experiments.
