Evidence for associated production of a single top quark and W boson in pp collisions at sqrt(s) = 7 TeV

Abstract

Evidence is presented for the associated production of a single top quark and W boson in pp collisions at sqrt(s) = 7 TeV with the CMS experiment at the LHC. The analyzed data corresponds to an integrated luminosity of 4.9 inverse femtobarns. The measurement is performed using events with two leptons and a jet originated from a b quark. A multivariate analysis based on kinematic properties is utilized to separate the t t-bar background from the signal. The observed signal has a significance of 4.0 sigma and corresponds to a cross section of 16 +5 -4 pb, in agreement with the standard model expectation of 15.6 +/-0.4 +1.0 -1.2 pb.

Figures (5)

• Figure 1: Leading order Feynman diagrams for single-top-quark production in the ${t}\mathrm{W}$ mode, the charge-conjugate modes are implicitly included.
• Figure 2: Feynman diagrams for ${t}\mathrm{W}$ single-top-quark production at next-to-leading order that are removed from the signal definition in the DR scheme, the charge-conjugate modes are implicitly included.
• Figure 3: Distributions of $H_T$ and the $p_{\mathrm{T}}$ of the system composed of the leptons, $E_{\mathrm{T}}^{\text{miss}}$ and the jet, in data and simulation after jet selection in the signal region (1j1t).
• Figure 4: Distribution of the BDT discriminant in the signal region (1j1t) in data and simulation.
• Figure 5: Event yields in data and simulation in the signal region (1j1t) and the two ${t}\overline{{t}}$-enriched control regions for the count-based analysis. Simulation yields are scaled to the outcome of the fit.