Search for New Physics in Dijet Angular Distributions in Proton-Proton Collisions at 13 TeV

A search for quark contact interactions, extra spatial dimensions, quantum black holes, and dark matter is presented in measurements of dijet angular distributions in proton-proton collisions at a center-of-mass energy of 13 TeV. The data were collected with the CMS detector at the LHC and correspond to an integrated luminosity of 35.9 inverse femtobarns. The dijet angular distributions are found to be in agreement with predictions from perturbative quantum chromodynamics that include electroweak corrections. Limits for a benchmark model where only left-handed quarks participate, contact interactions are excluded at the 95% confidence level up to a scale of 12.8 and 17.5 TeV, for destructive or constructive interference, respectively. The most stringent lower limits to date are set on the ultraviolet cutoff in the Arkani-Hamed-Dimopoulos-Dvali model of extra dimensions. In the Giudice-Rattazzi-Wells convention, the cutoff scale below 10.1 TeV is excluded. For the first time, lower limits between 2.0 and 4.6 TeV are set on the mass of a dark matter mediator for (axial-)vector mediators with universal quark coupling 1.0.