NEW PHYSICS AND RECENT HIGH-PRECISION ELECTROWEAK MEASUREMENTS

We analyze LEP and SLC data from the 1995 Winter Conferences for signa ls of new physics. We compare the data with the _Standard Model (SM) a s well as a number of test hypotheses concerning the nature of new phy sics: (i) nonstandard Zb ($) over bar b couplings, (ii) nonstandard Zf ($) over bar f couplings for the entire third generation, (iii) nonst andard oblique corrections, (iv) nonstandard lepton couplings, (v) gen eral nonstandard W and Z couplings to all fermions, as well as combina tions of the above. In most of our analyses, we leave the SM variables alpha(s) and m(t) as free parameters to see how the various types of new physics can affect their inferred values. We find that the best fi t (chi(2)/d.o.f. = 8.4/10) is obtained for the nonstandard Zb ($) over bar b couplings, which also give a 'low' value (0.112) for alpha(s). The SM also gives a good description of the Z data, having chi(2)/d.o. f. = 12.4/12. If alpha(2) is held fixed to the low-energy value 0.112, then we find that a combination of the nonstandard Zb ($) over bar b couplings is fit to lie more than four standard deviations away from z ero.