Measurement of the t-channel single top-quark cross section at 13 TeV

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 $42\,\,\rm pb^{-1}$. 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 $\sigma_{t-\rm ch}=274\pm 98\,{\rm (stat.)} \pm 52\,{\rm (syst.)}\pm 33\,{\rm (lumi.)}$. 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 $|V_{\mathrm{tb}}|=1.12\pm0.24\,{\rm (exp.)}\pm0.02\,{\rm (theo.)}$. The results are found to be in agreement with predictions by the standard model.