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PRECISION TESTS OF THE ELECTROWEAK INTERACTION WOLFGANG HOLLIKInstitut fur Theoretische Physik, Universitat KarlsruheD-76128 Karlsruhe, GermanyABSTRACTThe status of the electroweak Standard Model is reviewed in the light of recentprecision data and new theoretical results which have contributed to improve thepredictions for precision observables, together with the remaining inherent theoret-ical uncertainties. Consequences for possible new physics are also discussed.1. Standard Model entries:1.1. The fermionsThe family structure of the fermions is a manifestation of the SU(2)U(1) sym-metry. It has been strongly consolidated by several recent experimental informa-tions:Three generations of massless neutrinos: From the measurements of the Z line shapeat LEP the combined LEP value for the number of light neutrinos is 1 (universalcouplings assumed) N = 2:987  0:017 :m = 0 is consistent with the experimental mass limits experiments 2me 7:2 eV (95%C:L:); m 220 keV (90%C:L:); m 24MeV (95%C:L:) :Universality of neutral current couplings: The vector and axial vector coupling con-stants of the Z to e; ;  measured at LEP 1 show agreement with lepton universalityand with the Standard Model prediction (Figure 1).Recent results on (e) and (e) by the CHARM II Collaboration yield forthe  and e coupling constants 3geV  2g geV = 0:035  0:017geA  2g geA = 0:503  0:017;compatible with gleptV;A from LEP 1 under the assumption of lepton universality:gV? = 0:0366  0:0011gA? = 0:50123  0:00042 :invited talk at the XV Int. Conference on Physics in Collisions, Cracow, Poland, June 19951 Figure 1: 68% C.L. contours for the leptonic coupling constants from LEP, ref (1).Universality of charged current couplings: The  - CC universality can be expressedin terms of the ratio of the eective decay constants G for  ! ee and G for! ee to be unity in the Standard Model: GG!2 = Be
 mm 5 = 1 :The recent data on the  mass m , the  life