Measurement of the ${\rm t}{\rm \bar{t}}$ production cross section at 13 TeV in the all-jets final state

The top quark pair production cross section is measured in the all-jets decay channel using pp collisions at a centre-of-mass energy of 13 TeV at the LHC with the CMS detector. The data sample corresponds to an integrated luminosity of $2.53\,{\rm fb}^{-1}$ recorded in 2015. The inclusive ${\rm t}{\rm \bar{t}}$ production cross section is measured to be $834\pm 25(\rm stat)_{-104}^{+118}(\rm syst)\pm 23(\rm lumi)$ pb. Differential cross sections at detector level are measured as a function of the leading top quark transverse momentum, $p_{\rm T}$, and are compared to predictions from quantum chromodynamics. The spectrum is constructed by combining two distinct reconstruction approaches, targeting the low $p_{\rm T}$ (resolved top quark decay products), and the high $p_{\rm T}$ (boosted top quark decay products) regions. Finally, the cross sections are also reported at parton level, extrapolated to the full phase space. In all cases, the measured top quark $p_{\rm T}$ spectrum is found to be significantly softer than the theory predictions.