Model-independent analysis of nonstandard vertex parameters

We focus on two observables, whose experimental determination has been recently greatly improved at CERN LEP 1, that provide an operational definition of two new genuine vertex parameters called δ1,δ2. No other ''conventional'' parameters appear in the theoretical expressions. Thus, one can use the corresponding experimental information to obtain very general bounds on the effects of models of new physics on a sector that is orthogonal to that covered by previous analyses. These bounds are consistent with zero, although the central value of the experimental point in the parameter plane is still not discouraging the possibility of some effects. As an application of the method, a number of bounds are then calculated for specific models that would lead to modifications of the various vertices, in particular, models with an extra Z. These bounds are finally combined with those obtained by less general analyses, leading to values of the Z-Z' mixing angle well below the one percent level for a large number of cases