Abstract:
A combination of cross-section measurements for the associated production of a top quark and a $W$~bosonin proton-proton collisions at $\sqrt{s}=8$~TeV by the ATLAS and CMS experiments is presented. The two measurements are based on integrated luminosities of 20.3~fb$^{-1}$ and 12.2~fb$^{-1}$, respectively. The combined production cross section of a single top quark and a $W$~boson is determined as $\sigma_{tW} = 25.0\pm1.4\;(\text{stat.})\pm4.4\;(\text{syst.})\pm0.7\;(\text{lumi.})\,\,\text{pb} = 25.0\pm4.7\,\,\text{pb}$, in agreement with the NLO+NNLL expectation. A 95\% C.L. lower limit on the magnitude of the CKM matrix element $V_{tb}$ of $|V_{tb}|>0.79$ is extracted from the cross-section measurement.
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