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

# f${}^{R}_{1}$ INSPIRE search

VALUE CL% DOCUMENT ID TECN  COMMENT
• • • We do not use the following data for averages, fits, limits, etc. • • •
$\vert f{}^{R}_{1}/f{}^{L}_{2}\vert <0.37$ 95 1
 2017 BB
ATLS ${{\mathit t}}$-channel single top
$\vert f{}^{R}_{1}\vert < 0.16$ 95 2
 2017 G
CMS ${{\mathit t}}$-channel single-${{\mathit t}}$ prod.
$-0.20<Re(V_{tb} \text{ f}{}^{R}_{1})<0.23$ 95 3
 2012 BG
ATLS Constr. on ${{\mathit W}}{{\mathit t}}{{\mathit b}}$ vtx
$(\mathit V_{\mathit tb} \text{ f}{}^{R}_{1}){}^{2} < 0.93$ 95 4
 2012 E
D0 Single-top
$\vert f{}^{R}_{1}\vert ^2 < 0.30$ 95 5
 2012 I
D0 single-${{\mathit t}}$ + ${{\mathit W}}$ helicity
$\vert f{}^{R}_{1}\vert ^2 < 1.01$ 95 6
 2009 J
D0 $\vert$f${}^{L}_{1}\vert$ = 1, $\vert$f${}^{L}_{2}\vert =\vert$f${}^{R}_{2}\vert$=0
$\vert f{}^{R}_{1}\vert ^2 < 2.5$ 95 7
 2008 AI
D0 $\vert$f${}^{L}_{1}\vert ^2$ = $1.8$ ${}^{+1.0}_{-1.3}$
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 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. See this paper for constraints on other couplings not included here.
2  KHACHATRYAN 2017G based on 5.0 and 19.7 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ data at $\sqrt {s }$ = 7 and 8 TeV, respectively. A Bayesian neural network technique is used to discriminate between signal and backgrounds. This is a 95$\%$ CL exclusion limit obtained by a three-dimensional fit with simultaneous variation of (f${}^{L}_{1}$, f${}^{R}_{1}$, f${}^{R}_{2}$).
3  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{}$2j.
4  Based on 5.4 fb${}^{-1}$ of data. For each value of the form factor quoted the other two are assumed to have their SM value. Their Fig. 4 shows two-dimensional posterior probability density distributions for the anomalous couplings.
5  Based on 5.4 fb${}^{-1}$ of data in ${{\mathit p}}{{\overline{\mathit p}}}$ collisions at 1.96 TeV. Results are obtained by combining the limits from the ${{\mathit W}}$ helicity measurements and those from the single top quark production.
6  Based on 1 fb${}^{-1}$ of data at ${{\mathit p}}{{\overline{\mathit p}}}$ collisions $\sqrt {s }$ = 1.96 TeV. Combined result of the ${{\mathit W}}$ helicity measurement in ${{\mathit t}}{{\overline{\mathit t}}}$ events (ABAZOV 2008B) and the search for anomalous ${{\mathit t}}{{\mathit b}}{{\mathit W}}$ couplings in the single top production (ABAZOV 2008AI). Constraints when f${}^{L}_{1}$ and one of the anomalous couplings are simultaneously allowed to vary are given in their Fig. 1 and Table 1.
7  Result is based on 0.9 fb${}^{-1}$ of data at $\sqrt {s }$ = 1.96 TeV. Single top quark production events are used to measure the Lorentz structure of the ${{\mathit t}}{{\mathit b}}{{\mathit W}}$ coupling. The upper bounds on the non-standard couplings are obtained when only one non-standard coupling is allowed to be present together with the SM one, f${}^{L}_{1}$ = V${}^{*}_{ {{\mathit t}} {{\mathit b}} }$.
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 2017G
JHEP 1702 028 Search for Anomalous ${{\mathit W}}{\mathit {\mathit t}}{\mathit {\mathit b}}$ Couplings and Flavour-Changing Neutral Currents in ${{\mathit t}}$-Channel Single Top Quark Production in ${{\mathit p}}{{\mathit p}}$ Collisions at $\sqrt {s }$ = 7 and 8 TeV
JHEP 1206 088 Measurement of the ${{\mathit W}}$ Boson Polarization in Top Quark Decays with the ATLAS Detector
PL B713 165 Combination of Searches for Anomalous Top Quark Couplings with 5.4 ${\mathrm {fb}}{}^{-1}$ of ${{\mathit p}}{{\overline{\mathit p}}}$ Collisions
PL B708 21 Search for Anomalous Wtb Couplings in Single Top Quark Production in ${{\mathit p}}{{\overline{\mathit p}}}$ collisions at $\sqrt {s }$ = 1.96$~$TeV
PRL 102 092002 Search for Anomalous Top-Quark Couplings with the ${D0}$ Detector
PRL 101 221801 Search for Anomalous ${{\mathit W}_{{tb}}}$ Couplings in Single Top Quark Production
PRL 100 062004 Model-Independent Measurement of the ${{\mathit W}}$ Boson Helicity in Top Quark Decays at ${D0}$