${\boldsymbol {\boldsymbol t}}$-quark EW Couplings

${{\mathit W}}$ helicity fractions in top decays. ${{\mathit F}_{{0}}}$ is the fraction of longitudinal and ${{\mathit F}_{{+}}}$ the fraction of right-handed ${{\mathit W}}$ bosons. ${{\mathit F}_{{{V+A}}}}$ is the fraction of $\mathit V+\mathit A$ current in top decays. The effective Lagrangian (cited by ABAZOV 2008AI) has terms f${}^{L}_{1}$ and f${}^{R}_{1}$ for $\mathit V−\mathit A$ and $\mathit V+\mathit A$ couplings, f${}^{L}_{2}$ and f${}^{R}_{2}$ for tensor couplings with b$_{R}$ and b$_{L}$ respectively.

$\vert $f$_{LV}\sqrt {\vert V_{td}\vert ^2 + \vert V_{ts}\vert ^2 }\vert $

INSPIRE search
Assumed that the top-quark-related CKM matrix elements obey the relation $\vert V_{td}\vert ,\vert V_{ts}\vert $ ${}\ll$ $\vert V_{tb}\vert $ and a form factor f$_{LV}$ is determined for each production mode andcentre-of-mass energy.
• • We do not use the following data for averages, fits, limits, etc. • •
$0.24$ $\pm0.12$ 1
CMS ${{\mathit t}}$-channel single top
1  We report the square root of SIRUNYAN 2020AZ result based on 35.9 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ data at $\sqrt {s }$ = 13 TeV measured $\vert V_{td}\vert ^2$ + $\vert V_{ts}\vert ^2$ = $0.06$ $\pm0.06$ using final states enriched in single top quark ${{\mathit t}}$-channel events by releasing all constraints from unitarity of the CKM matrix within the SM. Under the standard model assumption of CKM unitarity,the values are found to be $\vert V_{tb}\vert $ $>$ 0.970 and $\vert V_{td}\vert ^2$ + $\vert V_{ts}\vert ^2$ $<$ 0.057, both at 95$\%$ CL.
PL B808 135609 Measurement of CKM matrix elements in single top quark $t$-channel production in proton-proton collisions at $\sqrt{s} = $ 13 TeV