Measurement of -channel Single-top-quark Production in Collisions at TeV with the ATLAS detector

The observation of the electroweak production of single-top-quarks is made using $255{\text{pb}}^{-1}$ of proton-proton collision data recorded at $\sqrt{s}=5.02$ TeV with the ATLAS detector at the Large Hadron Collider. An event selection is used to identify single-top-quark candidates arising from t-channel production with the top quark decaying semi-leptonically. Events passing the selection are then used to measure the inclusive cross-section for the combined production of single-top-quarks and antiquarks, $\sigma \left(tq+\overline{t}q\right)$, and the ratio ${R}_{t}$ between these two. They are measured to be $\sigma \left(tq+\overline{t}q\right)={27.1}_{-4.1}^{+4.4}{\left(\mathrm{stat}.\right)}_{-3.7}^{+4.4}\left(\mathrm{syst}.\right)$ pb and ${R}_{t}={2.73}_{-0.82}^{+1.43}{\left(\mathrm{stat}.\right)}_{-0.29}^{+1.01}\left(\mathrm{syst}.\right)$. The individual single-top-quark (tq) and single-top-antiquark ($\overline{t}q$) production cross-sections are measured to be $\sigma \left(tq\right)={19.8}_{-3.1}^{+3.9}{\left(\mathrm{stat}.\right)}_{-2.2}^{+2.9}\left(\mathrm{syst}.\right)$ pb and $\sigma \left(\overline{t}q\right)={7.3}_{-2.1}^{+3.2}{\left(\mathrm{stat}.\right)}_{-1.5}^{+2.8}\left(\mathrm{syst}.\right)$ pb. All measurements are in good agreement with the Standard Model predictions.