We report a measurement of the lifetime of the B0 meson based upon 29-GeV e+e- annihilation data taken with the Mark II detector at the SLAC storage ring PEP. The B0 mesons are tagged by their decays into D*- and D*+, where the D*- is tagged by its decay into -D 0. We reconstruct the decay vertices of 15 B0-meson candidates and measure the B0 lifetime to be 1.20-0.360.14+0.52+0.16 psec. © 1990 The American Physical Society.

Using an impact-parameter tag to select an enriched sample of Z0bb» events, we have measured the difference between the average charged multiplicity of bb» and all hadronic Z0 decays to be 2.11.8(stat) 0.6(syst) tracks per event. The resulting total (nonleading) charged multiplicity for Z0 bb» events is 23.1(12.0)1.8 0.6 tracks. A comparison of this nonleading multiplicity to hadronic multiplicity data in the range of 10 to 60 GeV supports the hypothesis of flavor-independent hadronic fragmentation, and yields a measurement of the average energy fraction of bottom hadrons in Z0 decays of xEb=0.620.100.04. © 1992 The American Physical Society.

We use data from the Mark II experiment at PEP to search for the process B→h0X for mh0 between 50 and 210 MeV/c2. No evidence for the Higgs boson is seen in this mass range. The limit obtained rules out the standard Higgs boson for masses between 70 and 210 MeV/c2 and significantly constrains extensions of the Higgs sector. © 1989.

A search for pair production of stable charged particles from Z decay has been performed with the Mark II detector at the SLAC Linear Collider. Particle masses are determined from momentum, ionization energy loss, and time-of-flight measurements. A limit excluding pair production of stable fourth-generation charged leptons and stable mirror fermions with masses between the muon mass and 36.3 GeV/c2 is set at the 95% confidence level. Pair production of stable supersymmetric scalar leptons with masses between the muon mass and 32.6 GeV/c2 is also excluded. © 1990 The American Physical Society.

We have measured the fraction of bb» events in hadronic Z0 decays, Rbb», using the vertex detector system of the Mark II detector at the SLAC Linear Collider. We tag bb» events by requiring the coincidence of three or more tracks with significant impact parameters. This tag is 50% efficient and results in a sample of 85% purity. We find Rbb»=0.251+0.049+0.030, in good agreement with other measurements and the standard model prediction. © 1991 The American Physical Society.

A precise measurement of the ratio R of the total cross section e+e-hadrons to the pointlike cross section e+e-+- at a center-of-mass energy of 29.0 GeV is presented. The data were taken with the upgraded Mark II detector at the SLAC storage ring PEP. The result is R=3.920.050.09. The luminosity has been determined with three independent luminosity monitors measuring Bhabha scattering at different angular intervals. Recent calculations of higher-order QED radiative corrections are used to estimate the systematic error due to missing higher-order radiative corrections in the Monte Carlo event generators. © 1991 The American Physical Society.

Data taken by the Mark II detector at the PEP storage ring was used to measure the rate of dilepton production in multihadronic events produced by e+e- annihilation at √s=29 GeV. We determine the probability that a hadron initially containing a b (b̄) quark decays to a positive (negative) lepton to be 0.17-0.08+0.15, with 90% confidence level limits of 0.06 and 0.38. © 1990.