EFFECT OF EXTRA NEUTRAL GAUGE BOSONS IN THE DIFFERENTIAL CROSS-SECTION OF E(-)-]MU(+)MU(-)()E()

The differential cross section of e(+)e(-) --> mu(+)mu(-) at the tree level depends on the scattering angle theta and shows a minimum at a p articular angle, theta(min). It is found that there is a large discrep ancy between theta(min) predicted in the standard model and the one in a class of grand unified theories that have extra neutral gauge boson s. Thus, the effect of extra neutral gauge bosons might be detected by measuring the angle theta(min) at which the differential cross sectio n is smallest. The discrepancy depends on the center of mass energy of the process, root s, and on the mass of the extra neutral gauge boson . Typically, when root s is about 150 GeV, which is available at LEP I I. the effect of the extra neutral gauge boson on theta(min) will be s ignificant if it exists.