Triple Gauge-boson Couplings in W pair Production via $e^+ e^-$ Annihilation

The start of LEP2 at energies above the threshold for W pair production has made it possible for the first time ever to study the fundamental non-Abelian gauge structure of the electroweak standard model directly in the very clean environment of e+e- collisions. In the general case the triple gauge-boson sector can be parametrised in an effective operator expansion and a set of 14 triple gauge-boson couplings are introduced to describe the strength of the different operator in the expansion. In this report we have investigated the precision to be expected on the triple gauge-boson couplings at 161 GeV using a generalised maximum likelihood method, which in addition to the usual maximum likelihood method includes information on the total number of events in the data sample. Using data taken by the ALEPH detector during the run in June to August, 1996, 6 semi-leptonic and 13 hadronic W+W- events were found --- in agreement with the standard model. Fitting the theoretical differential cross section for W pair production using a generalised maximum likelihood method, to the measured kinematical distributions, yields 95% confidence limits on the three triple gauge-boson couplings which are least bound by LEP1 data. The limits are in agreement with the standard model and comparable to the present limits from hadron colliders.