Abstract:
A measurement of the $t$-channel single top-quark cross section is performed using the very first LHC proton-proton collisions at 13 TeV with the CMS detector. The dataset corresponds to an integrated luminosity of 42 pb$^{-1}$. Events are selected with one muon in the final state. The signal is extracted from a fit to the pseudo-rapidity distribution of the recoiling jet. The inclusive cross section is measured to be $\sigma_{t-\rm ch} = $ 274 $\pm$ 98 (stat.) $\pm$ 52 (syst.) $\pm$ 33 (lumi.). The observed (expected) significance of the signal contribution is 3.5 (2.7) standard deviations with respect to the background-only hypothesis. The magnitude of the CKM matrix element $V_{\mathrm{tb}}$ is also calculated, yielding $|V_{\mathrm{tb}}|= $ 1.12 $\pm 0.24 (exp.) $\pm$ 0.02 (theo.). The results are found to be in agreement with predictions by the standard model.
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