Measurements of R and A search for heavy-Quark production in e+e- annihilation at s=50 and 52 GeV

Abstract

The ratio R of the cross section for e+e- annihilation into hadronic final states to the QED cross section for muon-pair production is measured to be 4.340.450.30 and 4.230.200.21 at c.m. energies of 50 and 52 GeV, respectively. From these values of R and an analysis of the event shapes we deduce a 95%-confidence-level upper limit for the production rate of new heavy charge +23e or -13e quarks to be 0.19 units of R. © 1988 The American Physical Society.