HADRON RADIATION IN TAU-PRODUCTION AND THE LEPTONIC Z-BOSON DECAY-RATE

Secondary radiation of hadrons from a tau-pair produced in electron-po sitron collisions may constitute an important obstacle for precision m easurements of the production cross section and of branching ratios. T he rate for real and virtual radiation is calculated and various distr ibutions are presented. For Z decays a comprehensive analysis is perfo rmed which incorporates real and virtual radiation of leptons. The cor responding results are also given for primary electron and muon pairs. Compact analytical formulae are presented for entirely leptonic confi gurations. Measurements of Z partial decay rates which eliminate all h adron and lepton radiation are about 0.3% to 0.4% lower than totally i nclusive measurements, a consequence of the O(alpha(2)) negative virtu al corrections that are enhanced by the third power of a large logarit hm.