Measurements of the cross section for the production of top quark pairs in association with a pair of jets from bottom quarks (σttbb) and in association with a pair of jets from quarks of any flavor or gluons (σttjj) and their ratio are presented. The data were collected in proton-proton collisions at a center-of-mass energy of 13 TeV by the CMS experiment at the LHC in 2016 and correspond to an integrated luminosity of 35.9 fb-1. The measurements are performed in a fiducial phase space and extrapolated to the full phase space, separately in the dilepton and lepton+jets channels, where lepton corresponds to either an electron or a muon. The results for the dilepton and lepton+jets channels, respectively, are σttjj = 2.36 ± 0.02 (stat) ± 0.20 (syst) pb and 31.0 ± 0.2 (stat) ± 2.9 (syst) pb, and for the cross section ratio 0.017 ± 0.001 (stat) ± 0.001 (syst) and 0.020 ± 0.001 (stat) ± 0.001 (syst). The values of σttbbare determined from the product of the σttjj and the cross section ratio, obtaining, respectively, 0.040 ± 0.002 (stat) ± 0.005 (syst) pb and 0.62 ± 0.03 (stat) ± 0.07 (syst) pb. These measurements are the most precise to date and are consistent, within the uncertainties, with the standard model expectations obtained using a matrix element calculation at next-to-leading order in quantum chromodynamics matched to a parton shower.
|State||Published - Mar 13 2020|