# ${\boldsymbol {\boldsymbol t}}$-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.

# ${{\boldsymbol F}_{{-}}}$ INSPIRE search

VALUE CL% DOCUMENT ID TECN  COMMENT
$\bf{ 0.320 \pm0.013}$ OUR AVERAGE
$> 0.264 \pm0.044$ 95 1
 2017 BB
ATLS ${{\mathit F}_{{-}}}$ = ${{\mathit f}_{{1}}}$(1 $−$ ${{\mathit f}_{{1}}^{+}}$)
$0.323$ $\pm0.008$ $\pm0.014$ 2
 2016 BU
CMS ${{\mathit F}_{{-}}}$ = B( ${{\mathit t}}$ $\rightarrow$ ${{\mathit W}_{{-}}}{{\mathit b}}$ )
$0.310$ $\pm0.022$ $\pm0.022$ 3
 2013 BH
CMS ${{\mathit F}_{{-}}}$ = B( ${{\mathit t}}$ $\rightarrow$ ${{\mathit W}_{{-}}}{{\mathit b}}$ )
$0.32$ $\pm0.04$ 4
 2012 BG
ATLS ${{\mathit F}_{{-}}}$ = B( ${{\mathit t}}$ $\rightarrow$ ${{\mathit W}_{{-}}}{{\mathit b}}$ )
1  AABOUD 2017BB based on 20.2 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ data at $\sqrt {s }$ = 8 TeV. Triple-differential decay rate of top quark in the ${{\mathit t}}$-channel single-top production is used to simultaneously determine five generalized ${{\mathit W}}{{\mathit t}}{{\mathit b}}$ couplings as well as the top polarization. No assumption is made for the other couplings. The authors reported ${{\mathit f}_{{1}}}$ = $0.30$ $\pm0.05$ and ${{\mathit f}_{{1}}^{+}}$ $<$ $0.120$ which we converted to ${{\mathit F}_{{-}}}$ = ${{\mathit f}_{{1}}}(1$ $−$ ${{\mathit f}_{{1}}^{+}}$). See this paper for constraints on other couplings not included here.
2  KHACHATRYAN 2016BU based on 19.8 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ data at $\sqrt {s }$ = 8 TeV using ${{\mathit t}}{{\overline{\mathit t}}}$ events with ${{\mathit \ell}}$ + $\not E_T$ + ${}\geq{}$4 jets(${}\geq{}$2 ${{\mathit b}}$). The errors of ${{\mathit F}_{{0}}}$ and ${{\mathit F}_{{-}}}$ are correlated with a correlation coefficient $\rho ({{\mathit F}_{{0}}}$, ${{\mathit F}_{{-}}}$) = $-0.87$. The result is consistent with the NNLO SM prediction of $0.311$ $\pm0.005$ for ${\mathit m}_{{{\mathit t}}}$ = $172.8$ $\pm1.3$ GeV.
3  Based on 5.0 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ data at $\sqrt {s }$ = 7 TeV. CHATRCHYAN 2013BH studied events with large $\not E_T$ and ${{\mathit \ell}}$ +${}\geq{}$4 jets using a constrained kinematic fit.
4  Based on 1.04 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ data at $\sqrt {s }$ = 7 TeV. AAD 2012BG studied events with large $\not E_T$ and either ${{\mathit \ell}}$ +${}\geq{}$4j or ${{\mathit \ell}}{{\mathit \ell}}$ +${}\geq{}$2j. The uncertainties are not independent, $\rho ({{\mathit F}_{{0}}},{{\mathit F}_{{-}}}$) = $-0.96$.
References:
 AABOUD 2017BB
JHEP 1712 017 Analysis of the $\mathit W_{tb}$ Vertex from the Measurement of Triple-Differential Angular Decay Rates of Single Top Quarks Produced in the t-Channel at $\sqrt {s }$ = 8 TeV with the ATLAS Detector
 KHACHATRYAN 2016BU
PL B762 512 Measurement of the ${{\mathit W}}$ Boson Helicity Fractions in the Decays of Top Quark Pairs to Lepton + Jets Final States Produced in ${{\mathit p}}{{\mathit p}}$ Collisions at $\sqrt {s }$ = 8 TeV
 CHATRCHYAN 2013BH
JHEP 1310 167 Measurement of the ${{\mathit W}}$-Boson Helicity in Top-Quark Decays from ${\mathit {\mathit t}}{\mathit {\overline{\mathit t}}}$ Production in Lepton+Jets Events in ${{\mathit p}}{{\mathit p}}$ Collisions at $\sqrt {s }$ = 7 TeV
JHEP 1206 088 Measurement of the ${{\mathit W}}$ Boson Polarization in Top Quark Decays with the ATLAS Detector