Searches for electroweak γ-Z-Z′ interference at the LEP2 e+e- collider

Indirect effects of the Z' boson in the process e(+)e(-) --> mu(+)mu(-) as implemented at the LEP2 electron-positron collider are investigated in terms of new integrated observables sigma(+/-). It is demonstrated that these observables furnish more definitive information about Z'-boson effects than the canonical observables sigma(mu mu) and A(FB) It is established that the deviations Delta sigma(+/-) induced by Z' bosons show a specific energy dependence, which is determined primarily by the parameters of the Standard Model. This permits making unambiguous model-independent predictions. In particular, two points, root s(+) approximate to 78 GeV and root s(-) approximate to 113 GeV, are determined at which, respectively, sigma(+) and sigma(-) vanish both in the Standard Model and in presence of the extra Z' boson. These energy values can be of use in searches for phenomenological manifestations of alternative sources of new physics that are different from Z'. (C) 2000 MAIK "Nauka/Interperiodica".