Measurement of the $t$-channel single top-quark production cross section at $\sqrt{s}=13$ TeV with the ATLAS detector and interpretations of the measurement

The $t$-channel is the dominant production channel for single top-quarks at the LHC. The total cross section of this process is measured by ATLAS in proton-proton collisions at a center-of-mass energy $\sqrt{s}=13$ TeV. The production cross sections for single top-quarks and single top-antiquarks are measured to be ${\sigma }_{tq}={\text{137}}_{-8}^{+8}$ pb and ${\sigma }_{\bar{t}q}={\text{84}}_{-5}^{+6}$ pb. For the combined cross section and the ratio of the cross sections $R_t$, ${\sigma }_{tq+\bar{t}q}={\text{221}}_{-13}^{+13}$ pb and $R_t={\text{1.636}}_{-0\text{.}034}^{+0\text{.}036}$ are obtained. As interpretations of the measurement, limits are set on the EFT operator $O_{Qq}^{3,1}$ and on the CKM matrix elements $\mathrm{\mid }{V}_{td}\mathrm{\mid }$, $\mathrm{\mid }{V}_{ts}\mathrm{\mid }$ and $\mathrm{\mid }{V}_{tb}\mathrm{\mid }$.