Prompt leptons from the decays of heavy quarks in the e+e- annihilation at energies of 35 and 43 GeV

Production and decays of heavy quarks in e+e- annihilations have been investigated with te CELLO detector in the energy range from 35 GeV up to the highest PETRA energies of 46.78 GeV. The semileptonic branching ratios and the charge asymmetries of b and c quarks, at √s=35 and 43 GeV have been simultaneously measured using, in addition to the lepton transverse momentum, correlated jet variables for quark flavour separation. We determined the charge asymmetries to be AFBb=-(22.2 ± 8.1)%, AFBc=-(12.9 ± 8.8)% at 35 GeV and AFBb=-(49.1 ± 16.5)%, AFBc=+(7.7 ± 14.0)% at 43 GeV, respectively. Taking B0anti B0 mixing into account, the combined measurements result in values for the axial vector couplings of the heavy quarks of ac=+(0.28 ± 0.45) and ab=-(1.26 ± 0.38) which are in good agreement with the standard model predictions of ac=+1 and ab=-1, respectively. We also measured the banti b and canti c production cross section at both centre of mass energies and give an upper limit for the B0 meson mixing parameters of χl<0.16 (90% C.L.) and lower limits in the 1-2 TeV range for the scale of a possible common electron-heavy quark compositeness from the measured asymmetries. Up to the maximum PETRA energies, we find no indication for new phenomena in the production of hadronic events with isolated leptons. (orig.)