Measurement of the t-channel single-top-quark production cross section and of the |Vtb| CKM matrix element in pp collisions at = 8 TeV

A bstract Measurements are presented of the t -channel single-top-quark production cross section in proton-proton collisions at = 8 TeV. The results are based on a data sample corresponding to an integrated luminosity of 19.7 fb −1 recorded with the CMS detector at the LHC. The cross section is measured inclusively, as well as separately for top (t) and antitop , in final states with a muon or an electron. The measured inclusive t -channel cross section is σ t -ch. = 83 . 6 ± 2 . 3 (stat.) ± 7 . 4 (syst.) pb. The single t and cross sections are measured to be σ t -ch. ( t ) = 53 . 8 ± 1 . 5 (stat.) ± 4 . 4 (syst.) pb and σ t -ch. = 27 . 6 ± 1 . 3 (stat.) ± 3 . 7 (syst.) pb, respectively. The measured ratio of cross sections is R t -ch. = σ t -ch. (t) /σ t -ch. = 1 . 95 ± 0 . 10 (stat.) ± 0 . 19 (syst.), in agreement with the standard model prediction. The modulus of the Cabibbo-Kobayashi-Maskawa matrix element V tb is extracted and, in combination with a previous CMS result at = 7 TeV, a value | V tb | = 0 . 998 ± 0 . 038 (exp.) ± 0 . 016 (theo.) is obtained.