Measurement of triple gauge-boson couplings at LEP energies up to 189 GeV

Abstract.

The triple gauge-boson couplings involving the W are determined using data samples collected with the ALEPH detector at mean centre-of-mass energies of 183 GeV and 189 GeV, corresponding to integrated luminosities of 57 pb$^{-1}$ and 174 pb$^{-1}$, respectively. The couplings, $g^Z_1$, $\kappa_\gamma$ and $\lambda_\gamma$, are measured using W-pair events, single-{\it W} production and single-$\gamma$ production. Each coupling is measured individually with the other two couplings fixed at their standard model value. Including ALEPH results from lower energies, the 95% confidence level intervals for the deviation to the standard model are

$-0.087 <\Delta{g}^{Z}_1 < 0.141$, $-0.200 < \Delta\kappa_\gamma < 0.258$, and $-0.062 < \lambda_\gamma < 0.147$.

Fits are also presented where two or all three couplings are allowed to vary. In addition, W-pair events are used to set limits on the C- or P-violating couplings $g^V_4$, $g^V_5$, ${\tilde{\kappa}_{V}}$, and ${\tilde{\lambda}_{V}}$, where V denotes either $\gamma$ or Z. No deviations from the standard model expectations are observed.