Determination of the strong coupling constant from the measurement of inclusive multijet event cross sections in pp collisions at $\sqrt{s} = 8~\mathrm{TeV}$

A measurement of inclusive multijet event cross sections is presented from proton-proton collisions recorded at $\sqrt{s} = 8\,$TeV with the CMS detector and corresponding to an integrated luminosity of $19.7\,\mathrm{fb}^{-1}$. Jets are reconstructed with the anti-k$_t$ clustering algorithm for a jet size parameter $R=0.7$ in a phase space region ranging up to jet transverse momenta $p_\mathrm{T}$ of $2.0\,$TeV and an absolute rapidity of $|y|=2.5$. The inclusive 2-jet and 3-jet event cross sections are measured as a function of the average $p_\mathrm{T}$ of the two leading jets. The data are well described by predictions at next-to-leading order in perturbative quantum chromodynamics and additionally are compared to several Monte Carlo event generators. The strong coupling constant at the scale of the Z boson mass is inferred from a fit of the ratio of the 3-jet over 2-jet event cross section giving $\alpha_s(M_Z) = 0.1150\,\pm0.0010\,\textrm{(exp)}\,\pm0.0013\,\textrm{(PDF)}\, \pm0.0015\,\textrm{(NP)}\,^{+0.0050}_{-0.0000}\,\textrm{(scale)}$.