Abstract
The cross section for the production of single top quarks in the t channel is measured in proton–proton collisions at 13TeV with the CMS detector at the LHC. The analyzed data correspond to an integrated luminosity of 2.2fb−1. The event selection requires one muon and two jets where one of the jets is identified as originating from a bottom quark. Several kinematic variables are then combined into a multivariate discriminator to distinguish signal from background events. A fit to the distribution of the discriminating variable yields a total cross section of 238±13(stat)±29(syst) pb and a ratio of top quark and top antiquark production of Rt-ch.=1.81±0.18(stat)±0.15(syst). From the total cross section the absolute value of the CKM matrix element Vtb is calculated to be 1.05±0.07(exp)±0.02(theo). All results are in agreement with the standard model predictions.
Highlights
The production of single top quarks provides a unique testing ground for the study of electroweak processes, the tWb vertex, as well as the measurement of the Cabibbo–Kobayashi– Maskawa (CKM) matrix element V tb
In the analysis described in this letter, the separation between signal and background processes is achieved using a multivariate analysis (MVA) technique
In addition to the presence of exactly one isolated muon, the signature of t-channel single top quark production is characterized by a substantial momentum imbalance associated to at least one neutrino, a jet arising from the hadronization of a bottom quark (b jet) from the top quark decay, and a light-quark jet — often produced in the forward region
Summary
The production of single top quarks provides a unique testing ground for the study of electroweak processes, the tWb vertex, as well as the measurement of the Cabibbo–Kobayashi– Maskawa (CKM) matrix element V tb. The other two processes, W-associated (tW) production and production via the s channel, amount to roughly 30% of the total single top quark production cross section at 13 TeV [8]. The CMS collaboration has performed√several measurements of this process using data collected at s = 7 and 8 TeV [5,9,10] This analysis is based on a data set obtained from proton–proton collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 2.2 fb−1. The cross section calculation of t-channel single top quark production can be performed in two different schemes [11,12,13]. The next-to-leading-order (NLO) calculations with Hathor v2.1 [14,15] in the 5FS result in cross section values of σt-ch.,t. No attempts are made to distinguish these two cases and the signal yield is corrected for the τ decay contributions using the corresponding theoretical branching ratio
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