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

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 and 174 pb, respectively. The couplings, , and , are measured using W-pair events, single-{\it W} production and single- 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 , , and . 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 , , , and , where V denotes either or Z. No deviations from the standard model expectations are observed.