Search for new physics with dijet angular distributions in proton-proton collisions at $\sqrt{s}=13~\mathrm{TeV}$ and constraints on dark matter and other models

A search is presented for new physics using measurements of dijet angular distributions from proton-proton collisions at $\sqrt{s}=13~\mathrm{TeV}$, constraining models of quark contact interactions, extra spatial dimensions, quantum black holes, and dark matter. The data collected with the CMS detector at the LHC correspond to an integrated luminosity of $35.9~\mathrm{fb}^{-1}$. The measured distributions are found to be in agreement with predictions from perturbative quantum chromodynamics (QCD) that include electroweak corrections. In a benchmark model, valid to next-to-leading order in QCD, in which only left-handed quarks participate, contact interactions are excluded up to a scale of 13.1 and 17.4 TeV for destructive or constructive interference, respectively. The most stringent lower limits to date are set on the scale of graviton exchange. In the Giudice$-$Rattazzi$-$Wells convention, virtual graviton exchange is excluded up to a scale of 10.6 TeV at 95$\%$ confidence. The production of quantum black holes is excluded for masses below 8.3 and 6.0 TeV, depending on the model. Vector and axial-vector mediators in a simplified model of interactions between quarks and dark matter particles with quark coupling $g_{\text{q}} = 1.0$, dark matter coupling $g_{\text{DM}} = 1.0$, and masses between 2.5 and 5.0 TeV are excluded.