${{\boldsymbol Z}}$ AXIAL-VECTOR COUPLINGS

These quantities are the effective axial-vector couplings of the ${{\mathit Z}}$ to charged leptons. Their magnitude is derived from a measurement of the ${{\mathit Z}}$ lineshape and the forward-backward lepton asymmetries as a function of energy around the ${{\mathit Z}}$ mass. The relative sign among the vector to axial-vector couplings is obtained from a measurement of the ${{\mathit Z}}$ asymmetry parameters, ${{\mathit A}_{{e}}}$, ${{\mathit A}_{{\mu}}}$, and ${{\mathit A}_{{\tau}}}$. By convention the sign of $\mathit g{}^{{{\mathit e}}}_{\mathit A}$ is fixed to be negative (and opposite to that of $\mathit g{}^{{{\mathit \nu}_{{e}}}}$ obtained using ${{\mathit \nu}_{{e}}}$ scattering measurements). For the light quarks, the sign of the couplings is assigned consistently with this assumption. The fit values quoted below correspond to global nine- or five-parameter fits to lineshape, lepton forward-backward asymmetry, and ${{\mathit A}_{{e}}}$, ${{\mathit A}_{{\mu}}}$, and ${{\mathit A}_{{\tau}}}$ measurements. See the note ``The ${{\mathit Z}}$ boson'' and ref. LEP-SLC 2006 for details. Where ${{\mathit p}}{{\overline{\mathit p}}}$ and ${{\mathit e}}{{\mathit p}}$ data is quoted, OUR FIT value corresponds to a weighted average of this with the LEP/SLD fit result.

$\boldsymbol g{}^{{{\boldsymbol \tau}}}_{\boldsymbol A}$ INSPIRE search

VALUE EVTS DOCUMENT ID TECN  COMMENT
$\bf{ -0.50204 \pm0.00064}$ OUR FIT
$-0.50165$ $\pm0.00124$ 151.5K 1
ABBIENDI
2001O
OPAL ${\it{}E}^{\it{}ee}_{\rm{}cm}$= $88 - 94$ GeV
$-0.5023$ $\pm0.0017$ 103.0k 2
ACCIARRI
2000C
L3 ${\it{}E}^{\it{}ee}_{\rm{}cm}$= $88 - 94$ GeV
$-0.50216$ $\pm0.00100$
BARATE
2000C
ALEP ${\it{}E}^{\it{}ee}_{\rm{}cm}$= $88 - 94$ GeV
1  ABBIENDI 2001O use their measurement of the ${{\mathit \tau}}$ polarization in addition to the lineshape and forward-backward lepton asymmetries.
2  ACCIARRI 2000C use their measurement of the ${{\mathit \tau}}~$polarization in addition to forward-backward lepton asymmetries.
  References:
ABBIENDI 2001O
EPJ C21 1 Precision Neutral Current Asymmetry Parameter Measurements from the ${{\mathit \tau}}$ Polarization at LEP
ACCIARRI 2000C
EPJ C16 1 Measurements of Cross Sections and Forward Backward Asymmetries at the ${{\mathit Z}}$ Resonance and Determination of Electroweak Parameters
BARATE 2000C
EPJ C14 1 Measurement of the ${{\mathit Z}}$ Resonance Parameters at LEP