Measurement of Triple-Differential Dijet Cross Sections at $\sqrt{s}=8\,$TeV with the CMS Detector and Constraints on Parton Distribution Functions

A measurement of triple-differential dijet cross sections at a centre-of-mass energy of $\sqrt{s} = 8\,$TeV is presented using $19.7\,$fb$^{-1}$ of data collected with the CMS detector in proton-proton collisions at the LHC. The cross sections are measured as a function of the average transverse momentum, half the rapidity separation, and the boost of the two leading jets. The cross sections are unfolded for detector effects and compared to calculations in perturbative quantum chromodynamics at next-to-leading order accuracy complemented with electroweak and nonperturbative corrections. Constraints on the parton distribution functions are derived and the strong coupling constant is determined to be $\alpha_s(M_Z) = 0.1199\,\pm{0.0015}\,(\mathrm{exp})\, _{-0.0020}^{+0.0031}\,(\mathrm{theo})$.