CMS-PAS-TOP-20-003

CMS-PAS-TOP-20-003
Measurement of the cross section of top quark pair production with additional charm jets using the dileptonic final state in pp collisions at $\sqrt{s}= $ 13 TeV
CMS Collaboration
September 2020

Abstract: For the first time, a measurement of the inclusive cross section of top quark pair ($\mathrm{t}\bar{\mathrm{t}}$) production with two additional charm jets is presented. The measurement is performed using the dileptonic decay channel of the top quark pairs produced in proton-proton collisions at a centre-of-mass energy of 13 TeV. The used dataset corresponds to an integrated luminosity of 41.5 fb$^{-1}$, collected with the CMS detector at the LHC. A neural network is trained to distinguish between top quark pair events with additional c jets ($\mathrm{t}\bar{\mathrm{t}}\mathrm{c}\bar{\mathrm{c}}$), b jets ($\mathrm{t}\bar{\mathrm{t}}\mathrm{b}\bar{\mathrm{b}}$), and light-flavour jets ($\mathrm{t}\bar{\mathrm{t}}\text{LF}$), based on observables related to dedicated charm jet identification algorithms, as well as kinematic properties of the event. By means of a template fitting procedure using simulated and observed neural network outputs, the inclusive $\mathrm{t}\bar{\mathrm{t}}\mathrm{c}\bar{\mathrm{c}}$, $\mathrm{t}\bar{\mathrm{t}}\mathrm{b}\bar{\mathrm{b}}$, and $\mathrm{t}\bar{\mathrm{t}}\text{LF}$ cross sections are simultaneously extracted, together with their ratios to the inclusive $\mathrm{t}\bar{\mathrm{t}}$ + two jets cross section. This results in a fully coherent treatment of different additional jet flavours in the production of $\mathrm{t}\bar{\mathrm{t}}$ + two jets, and provides the first measurement of the $\mathrm{t}\bar{\mathrm{t}}\mathrm{c}\bar{\mathrm{c}}$ process with a measured cross section of 0.152 $\pm$ 0.022 (stat.) $\pm$ 0.019 (syst.) pb in the fiducial phase space and 7.43 $\pm$ 1.07 (stat.) $\pm$ 0.95 (syst.) pb in the full phase space.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; These preliminary results are superseded in this paper, Submitted to PLB. The superseded preliminary plots can be found here.

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