Measurement of the differential ttbar production cross section for high-pt top quarks in e/mu+jets final states at 8 TeV

The differential top-antitop quark production cross section is measured for top quarks with high transverse momentum in $\mathrm{pp}$ collisions at a center-of-mass energy of 8 TeV. The data sample was collected with the CMS detector during 2012 and corresponds to an integrated luminosity of $19.7 \pm 0.5$ fb$^{-1}$. The measurement is performed for events in e/$\mu$+jets final states where the hadronically decaying top quark is reconstructed as a single large-radius jet and identified as a top candidate using jet substructure techniques. The integrated cross section is measured at particle-level within a fiducial region resembling the detector-level selection as well as at parton-level. At particle-level, the cross section is measured to be $\sigma_{\rm t\bar{t}} = 1.28 \pm 0.09 ~({\rm stat+syst}) \pm 0.10 ~({\rm PDF}) \pm 0.09 ~({\rm Q^2}) \pm 0.03 ~({\rm lumi)~pb}$ for $p_{\rm T} > 400~{\rm GeV}$. At parton-level, it is measured to be $\sigma_{\rm t\bar{t}} = 1.44 \pm 0.10 ~({\rm stat+syst}) \pm 0.13 ~({\rm PDF}) \pm 0.15 ~({\rm Q^2}) \pm 0.04 ~{\rm (lumi)~pb}$, 14$\%$ lower than the estimate from $\mathrm{t \bar{t}}$ events simulated using Powheg. The hadronic top-jet candidate $p_{\rm T}$ distribution is corrected for detector effects to extract normalized differential cross sections at particle- and parton-level.