#### ${\mathit {\mathit t}}$-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$_{LV}V_{tb}\vert$

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 and centre-of-mass energy.
VALUE DOCUMENT ID TECN  COMMENT
 $\bf{ 0.995 \pm0.021}$ OUR AVERAGE
$0.988$ $\pm0.024$ 1
 2020 AZ
CMS 13 TeV, ${{\mathit t}}$ -channel single top
$1.02$ $\pm0.04$ $\pm0.02$ 2
 2019 R
LHC ATLAS + CMS at 7, 8 TeV
 1 SIRUNYAN 2020AZ based on 35.9 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ data at $\sqrt {s }$ = 13 TeV. Final states enriched in single top quark ${{\mathit t}}$ -channel events are used. Several theories beyond the standard model are considered, and by releasing all constraints among the involved parameters. 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.
 2 The combination of single-top production cross-section measurements in the ${{\mathit t}}$ -channel, ${{\mathit t}}{{\mathit W}}$ , and ${{\mathit s}}$ -channel production modes from ATLAS and CMS at $\sqrt {s }$ = 7 and 8 TeV.
References:
 SIRUNYAN 2020AZ
PL B808 135609 Measurement of CKM matrix elements in single top quark $t$-channel production in proton-proton collisions at $\sqrt{s} =$ 13 TeV
 AABOUD 2019R
JHEP 1905 088 Combinations of single-top-quark production cross-section measurements and |f$_{LV}$V$_{tb}$| determinations at $\sqrt{s}$ = 7 and 8 TeV with the ATLAS and CMS experiments