New Results on Heavy Flavor Production from PETRA

Abstract

I report on recent results obtained by experiments at the e⁺e^- storage ring PETRA. Data collected at c.m.s. energies between 30 and 46.2 GeV are analyzed to single out e⁺e^- → $c\overline c (b\overline b )$($[b\overline b$) tagged by the semileptonic decay of the quarks into muons. The transverse momenta of these muons with respect to the quark direction as well as the event shape allow for an efficient separation of the sample into its b and c contents and thus for a measurement of the c and b semileptonic branching ratios. The longitudinal momentum spectrum gives information about their fragmentation properties. Charm quark identification is also obtained by observing high momentum D* mesons among its fragmentation products. Both methods allow for a measurement of the forward-backward charge assymetry in b and c production, found to be in agreement with the usual assignment of weak isopsin for these quarks and thus indicating that the b quark is member of a doublet. The absence of flavor changing neutral current b decays also supports the hypothesis tat a top quark shoul exist. No indication of $[t\overline t$ resonance production is however observed at PETRA up to $sqrt s$=45.2 GeV