Non-linearities in estimators of trilinear gauge couplings that use total event rate

The total event rate of WW and single W production represents an important source of information on trilinear gauge couplings (TGC) at LEP 2. Present LEP analyses combine this information with the study of the four-fermion final-state angular distributions by means of an extended maximum likelihood (EML) estimator. In general, it can be shown that the inclusion of total event rate induces nonlinearities in the TGC estimators. In this letter, these biases are computed semi-analytically and calculations are carried out for typical LEP analyses at 161, 172 and 183 GeV. (9 refs).