# ${{\boldsymbol Z}}$ 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.

# $\boldsymbol g{}^{{{\boldsymbol e}}}_{\boldsymbol A}$ INSPIRE search

VALUE EVTS DOCUMENT ID TECN  COMMENT
$\bf{ -0.50111 \pm0.00035}$ OUR FIT
$-0.528$ $\pm0.123$ $\pm0.059$ 5026 1
 2005 M
CDF ${\it{}E}^{\it{}p\overline{\it{}p}}_{\rm{}cm}$= 1.96~TeV
$-0.50062$ $\pm0.00062$ 137.0K 2
 2001 O
OPAL ${\it{}E}^{\it{}ee}_{\rm{}cm}$= $88 - 94$ GeV
$-0.5015$ $\pm0.0007$ 124.4k 3
 2000 C
L3 ${\it{}E}^{\it{}ee}_{\rm{}cm}$= $88 - 94$ GeV
$-0.50166$ $\pm0.00057$
 2000 C
ALEP ${\it{}E}^{\it{}ee}_{\rm{}cm}$= $88 - 94$ GeV
$-0.4977$ $\pm0.0045$ 4
 1995 J
SLD ${\it{}E}^{\it{}ee}_{\rm{}cm}$= $91.31$ GeV
1  ACOSTA 2005M determine the forward--backward asymmetry of ${{\mathit e}^{+}}{{\mathit e}^{-}}$ pairs produced via ${{\mathit q}}$ ${{\overline{\mathit q}}}$ $\rightarrow$ ${{\mathit Z}}$ / ${{\mathit \gamma}^{*}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit e}^{-}}$ in 15 M( ${{\mathit e}^{+}}{{\mathit e}^{-}}$ ) effective mass bins ranging from 40~GeV to~600 GeV. These results are used to obtain the vector and axial--vector couplings of the ${{\mathit Z}}$ to ${{\mathit e}^{+}}{{\mathit e}^{-}}$ , assuming the quark couplings are as predicted by the standard model. Higher order radiative corrections have not been taken into account.
2  ABBIENDI 2001O use their measurement of the ${{\mathit \tau}}$ polarization in addition to the lineshape and forward-backward lepton asymmetries.
3  ACCIARRI 2000C use their measurement of the ${{\mathit \tau}}~$polarization in addition to forward-backward lepton asymmetries.
4  ABE 1995J obtain this result combining polarized Bhabha results with the $\mathit A_{\mathit LR}$ measurement of ABE 1994C. The Bhabha results alone give $-0.4968$ $\pm0.0039$ $\pm0.0027$.
References:
 ACOSTA 2005M
PR D71 052002 Measurement of the Forward-Backward Charge Asymmetry of Electron-Positron Pairs in ${{\overline{\mathit p}}}{{\mathit p}}$ Collisions at $\sqrt {s }$ = 1.96 TeV
 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
 ABE 1995J
PRL 74 2880 Polarized Bhabha Scattering a Precision Measurement of the Electron Neutral Current Couplings