M. Breidenbach

Observation of the radiative transition ψ → γE(1420)

Abstract We have observed a radiative transition from the ψ to a state decaying into K S K ± π ∓ , with mass M = 1.44 −0.015 +0.01 GeV/ c 2 and width Γ = 0.05 −0.02 +0.03 GeV/ c 2 . We tentatively identify this state as the E(1420). Assuming that this state is an isospin singlet, we have determined the branching fraction product B(ψ → γ E ) × B( E × K K π) = (3.6 ± 1.4) × 10 −3 .

Properties of anomalous eμ events produced in e+e− annihilation☆☆☆

Abstract We present the properties of 105 events of the form e + + e − → e +- + μ ∓ + missing energy, in which no other charged particles or photons are detected. The simplesthypothesis compatible with all the data is that these events come from the production of a pair of heavy leptons, the mass of the lepton being in the range 1.6 to 2.0 GeV/ c 2

D and D meson production near 4 GeV in e+e− annihilation

Abstract We have studied momentum spectra for D0 ( D 0) and D± mesons produced near 4 GeV in e+e− annihilation and find that production is dominated by two-body reactions involving D and D∗ states where the D∗ (charged and neutral) have masses near 2.01 GeV/c2. A detailed study of D momentum spectra near Ecm = 4.028 GeV allows determination of masses and branching ratios of D and D∗ states. Lastly we find that events containing a D0 meson conserve strangeness, thus establishing upper limits on D0- D 0 mixing and on the effects of charm changing neutral currents.

A measurement of the cross section for four-pion production in λλ collisions at spear☆

Abstract We present a measurement of the cross section for the reaction e + e − → e + e − π + π − π + π − at SPEAR. This channel is found to be large and dominated by the process γγ → ϱ 0 ϱ 0 → π + π − π + π − . The cross section, which is small just above the four-pion threshold, exhibits a large enhancement near the ϱ 0 ϱ 0 threshold.

Observations of S∗ → π+π−in ψ decay

Abstract Copious production of S ∗ decaying into π + π − is observed in ψ decay. (974 ± 4 - i 14 ± 5) MeV, consistent with the parameters extracted from couplede channel; fits to pheripheral π + π − and K + K − production experiments. The inclusive branching ratio for ψ → S ∗ + X is found to be (0.42 ± 0.08)%.

Overview of the SLD

The SLD is a second generation detector for the SLAC Linear Collider (SLC). It is optimized for Z° physics and exploration of new physics in the Z° energy region. The SLD will have a CCD vertex detector, high resolution drift chambers for momentum measurement, a ¿erenkov Ring Imaging Detector for particle identification, and calorimetry based on lead/liquid argon followed by an iron/gas system. The detector covers the full solid angle.

Limits on strength of neutral currents from e/sup +/e/sup -/. -->. mu. /sup +/. mu. /sup -/

The reaction e/sup +/e/sup -/ ..-->.. ..mu../sup +/..mu../sup -/ has been measured in the center-of-mass energy range 5.8--7.4 GeV. The polar-angle asymmetry agrees with second-order quantum electrodynamics. From this a 95% confidence limit of M/sub z/ > 53g/sub a//e GeV is placed on the mass to coupling constant ratio for a neutral vector boson.

K° production in e+e- annihilation

Abstract The production of enutral kaons in e + e − annihilation has been measured for c.m. energies between 3.4 GeV and 7.6 GeV. Near 4 GeV the inclusive K S cross section shows an increase and structure similar to total hadron production. Roughly 40–45% of all hadronic final states contain kaons, except at 4.028 GeV and 4.415 GeV, where a significantly larger kaon fraction is observed.

Properties of the proposed τ charged lepton

Abstract The anomalous eμ and 2-prong μx events produced in e + e − annihilation are used to determine the properties of the proposed τ charged lepton. We find the τ mass is 1.90 ± 0.10 GeV/ c 2 ; the mass of the associated neutrino, ν τ , is less than 0.6 GeV/ c 2 with 95% confidence; V - A coupling is favored over V + A coupling for the τ − ν τ current; and the leptonic branching ratios are 0.186 ± 0.010 ± 0.028 from the eμ events and 0.175 ± 0.027 ± 0.030 from the μx events where the first error is statistical and the second is systematic.

A study of the decayτ−→π−μτ

We present a high statistics measurement of the branching ratio for the decay τ-→π-μτ using data obtained with the Mark II detector at the SLAC e+e- storage ring SPEAR. We have used events from the center-of-mass energy region 3.52 to 6.7 GeV to determine that B(τ-→π-μτ)=0.117±0.004±0.018. From electron-muon events in the same data sample, we have determined that B(τ-→π-μτ) B(τ-→e--μeμτ)=0.66±0.03±0.11. We present measurements of the mass and spin of the τ and the mass of the τ neutrino based, for the first time, on a hadronic decay mode of the τ.