We have searched 205 pb-1 of s =29 GeV data from the Mark II detector at the SLAC e+e- storage ring PEP for events which may signify the existence of a new lepton pair (L-,L0) where the L0 may be massive, but does not exceed the L- mass. Three event signatures for L+L- decay are examined: (i) e, (ii) (e or)(+4), and (iii) (e or )(3+0). The numbers of signature events are found to be in good agreement with Monte Carlo simulations of known background sources. The ranges of L- and L0 masses for which new lepton pairs are excluded are obtained using a likelihood-ratio method to compare the number of observed signature events to the expected background, and to the expected background plus Monte Carlo predictions of (L-,L0) signals. © 1989 The American Physical Society.

The τ lifetime was measured with the Mark II vertex detector at the storage ring PEP. ττ=(3.20±0.41±0.35)×10-13 sec was found, which agrees well with e-μ-τ university. © 1983 The American Physical Society.

In a study of (3684) radiative decays with the Mark II detector at SPEAR, the decay sequence c (2980) is observed, with the c (2980) decaying into several completely reconstructed hadronic modes. A mass M=29808 MeV/c2 and a width <40 MeV/c2 (90%) confidence level) are obtained, and estimates of some of the decay branching ratios are presented. © 1980 The American Physical Society.

The inclusive and 0 momentum distributions at the have been measured. Using these data and estimates of production, it is found that (4.1 0.8)% of decays contain a direct photon with energy greater than 60% of the beam energy. The expected momentum distribution for direct photons calculated to lowest order in quantum chromodynamics is qualitatively different from that observed in the data. © 1980 The American Physical Society.

The branching fractions for the major decay modes of the lepton are measured from a sample of tagged decays selected from +- pairs produced in e+e- annihilation. The decay products of one member of the +- pair are used to identify the event. The opposite member of the pair is then included in the sample if it satisfies an invariant-mass cut and a charged-multiplicity cut. In this way, we attempt to select an unbiased sample of decays. The sample is divided into categories based on charged- and neutral-particle multiplicities, and charged-particle identification. The branching fractions are measured simultaneously, with an unfold technique and a maximum-likelihood fit, with the sum of the branching fractions constrained to be unity. The branching fractions for the decay modes - K- and - K*- are fixed at the world averages in the fit. The following branching fractions are measured: B(-e) =(19.10.81.1)%, B(-' - )=(18.30.90.8)%, B(-) =(10.01.1 *1,4)%, B(-0) =(25.81.72.5)%, B(-(n0, n>1))=(12.01.42.5)%, B(-+-) =(6.7 0.80.9)%, and B(-+- (n0,n>0)) =(6.10.80.9)%. The total branching fraction to one charged pion plus at least one neutral hadron is measured to be (37.81.21.0)%. Limits on allowed decay modes involving the meson are discussed. © 1987 The American Physical Society.

We have made a detailed comparison of the charged-particle flow in three-jet events (e+e-qq»g) and radiative two-jet events (e+e-qq») from e+e- annihilation at Ec.m.=29 GeV. Accurate comparisons can be made because these two event types have similar topologies. In the angular region between the quark and antiquark jets, we observe substantially fewer charged tracks in the two-jet events than in the radiative three-jet events. © 1986 The American Physical Society.

We update our previous analysis of the 3±01/2 decay mode by the addition of new data to obtain an improved upper limit on the 1/2 mass of 143 MeV/c2 at the 95% confidence level. © 1985 The American Physical Society.