${{\boldsymbol Z}}$ ASYMMETRY PARAMETERS

For each fermion-antifermion pair coupling to the ${{\mathit Z}}$ these quantities are defined as
$\mathit A_{\mathit f}$ = ${2 {\it g}^{\it f}_{\it V} {\it g}^{\it f}_{\it A}\over ({\it g}^{\it f}_{\it V}){}^{2}+({\it g}^{\it f}_{\it A}){}^{2}}$
where ${\it g}^{\it f}_{\it V}$ and ${\it g}^{\it f}_{\it A}$ are the effective vector and axial-vector couplings. For their relation to the various lepton asymmetries see the note ``The ${{\mathit Z}}$ boson'' and ref. LEP-SLC 2006 .

$\boldsymbol A_{{{\boldsymbol s}}}$ INSPIRE search

The SLD Collaboration directly extracts this quantity by a simultaneous fit to four measured ${{\mathit s}}$-quark polar angle distributions corresponding to two states of ${{\mathit e}^{-}}$ polarization (positive and negative) and to the ${{\mathit K}^{+}}{{\mathit K}^{-}}$ and ${{\mathit K}^{\pm}}{{\mathit K}_S^0}$ strange particle tagging modes in the hadronic final states.
VALUE EVTS DOCUMENT ID TECN  COMMENT
$0.895$ $\pm0.066$ $\pm0.062$ 2870 1
ABE
2000D
SLD ${\it{}E}^{\it{}ee}_{\rm{}cm}$= $91.2$ GeV
1  ABE 2000D tag ${{\mathit Z}}$ $\rightarrow$ ${{\mathit s}}{{\overline{\mathit s}}}$ events by an absence of ${{\mathit B}}$ or ${{\mathit D}}$ hadrons and the presence in each hemisphere of a high momentum ${{\mathit K}^{\pm}}$ or ${{\mathit K}_S^0}$ .
  References:
ABE 2000D
PRL 85 5059 First Direct Measurement of the Parity Violating Coupling of the ${{\mathit Z}^{0}}$ to the ${\mathit {\mathit s}}$ Quark