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.

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 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.

Data taken by the Mark II detector at the SLAC e+e- storage ring PEP was used to search for exclusive decays of D and B mesons into two charged leptons plus a charged pion or kaon. All possible charge and lepton combinations consistent with charge conservation were considered and no evidence for any signals was found. We obtain upper limits for the various branching ratios ranging from 2.5×10-3 to 9.2×10-3, at a 90% confidence level. Some of these limits can be used to constrain leptoquark masses in various models. © 1990 The American Physical Society.

Production rates of multijet hadronic final states are studied in e+e- annihilation at 29 GeV center of mass energy. QCD shower model calculations with exact first order matrix element weighting at the first gluon vertex are capable of reproducing the observed multijet event rates over a large range of jet pair masses. The method used to reconstruct jets is well suited for directly comparing experimental jet rates with parton rates calculated in perturbative QCD. Evidence for the energy dependene of αs is obtained by comparing the observed production rates of 3-jet events with results of similar studies performed at higher center of mass energies. © 1989 Springer-Verlag.

We have searched for the annihilation of e+e- into the exclusive channels e and at s =29 GeV, using 226 and 133 pb-1, respectively, of data taken with the Mark II detector at the SLAC storage ring PEP. The resulting candidate sample is compatible with the expected background from pair production. Our analysis yields 95%-C.L. cross-section limits of e/<1.8×10-3 and /<6.1×10-3, where is the QED cross section for production of a lepton pair. This is the first high-Q2 test of lepton-flavor conservation involving leptons. © 1991 The American Physical Society.

Multihadronic e+e- annihilation events at a center-of-mass energy of 29 GeV have been studied with both the original (PEP 5) Mark II and the upgraded Mark II detectors. Detector-corrected distributions from global shape analyses such as aplanarity, Q2-Q1, sphericity, thrust, minor value, oblateness, and jet masses, and inclusive charged-particle distributions including x, rapidity, p, and particle flow are presented. These distributions are compared with predictions from various multihadron event models which use leading-logarithmic shower evolution or QCD matrix elements at the parton level and string or cluster fragmentation for hadronization. The new generation of parton-shower models gives, on the average, a better description of the data than the previous parton-shower models. The energy behavior of these models is compared to existing e+e- data. The predictions of the models at a center-of-mass energy of 93 GeV, roughly the expected mass of the Z0, are also presented. © 1988 The American Physical Society.

We have studied the energy-energy correlation in e+e- annihilation into hadrons at s =29 GeV using the Mark II detector at the SLAC storage ring PEP. We find to O(s2) that s=0.1580.0030.008 if hadronization is described by string fragmentation. Independent fragmentation schemes give s=0.100.14, and give poor agreement with the data. A leading-log shower fragmentation model is found to describe the data well. © 1988 The American Physical Society.

We have measured the mass of the Z boson to be 91.14±0.12 GeV/c2, and its width to be 2.42-0.35+0.45 GeV. If we constrain the visible width to its standard-model value, we find the partial width to invisible decay modes to be 0.46±0.10 GeV, corresponding to 2.8±0.6 neutrino species, with a 95%-confidence-level upper limit of 3.9. © 1989 The American Physical Society.