A. D. Johnson

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 .

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.

Pion pair production in photon-photon collisions at spear

Abstract We report a measurement of the cross section for the process γγ → π + π − at invariant masses 500 MeV/ c 2 m ππ c 2 . A value for the radiative width of the f(1270) tensor meson Γ f→ γγ = 3.6 ± 0.3 ± 0.5 KeV (helicity λ = 2) has been obtained from a fit to the observed ππ mass spectrum.

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)%.

Observation of the Decay 00

The prompt photon decay psi(3095)..--> gamma pi../sup +/..pi../sup -/..pi../sup +/..pi../sup -/ has been studied with the Mark II detector at SPEAR. This channel is found to contain a ..gamma..rho/sup 0/rho/sup 0/ component with rho/sup 0/rho/sup 0/ masses concentrated between 1.4 and 2.0 GeV/c/sup 2/. The branching fraction for the psi..--> gamma..rho/sup 0/rho/sup 0/ decay with masses less than 2.0 GeV/c/sup 2/ is measured to be (1.25 +- 0.35 +- 0.40) x 10/sup -3/.The prompt photon decay (3095)+-+- has been studied with the Mark II detector at SPEAR. This channel is found to contain a 00 component with 00 masses concentrated between 1.4 and 2.0 GeV/c2. The branching fraction for the 00 decay with masses less than 2.0 GeV/c2 is measured to be (1.25±0.35±0.40)×10-3.

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.

D meson production and decay in e+e− annihilation at 4.03 and 4 GeV c.m. energy☆

Abstract Decay modes of the charmed mesons, D 0 and D + , are studied in e + e − annihilation data at 4.03 and 4.41 GeV c.m. energy. The products of cross section times branching ratio are measured for the K − π + , K − π + π + π − , K S π + π − and K − π + π + final states. Upper limits are established for the Cabibbo forbidden decays via π + π − , K + K − , K + K − π + , K + π + π − and π + π − π + . The K − π + π + π − final state is shown to be dominated by K − π + ρ 0 .

A search for stable particles heavier than the proton and for q = 2/3 quarks produced in e+ e- annihilation

Abstract We have searched 1.4 × 10 6 e + e − annihilation events for particles with 1–3 GeV/ c 2 mass and charge Q = − 2 3 from the processes e + e − →q q X and e + e − → q q . Upper limits of RQ ∼ 10 −4 for each process are presented which improve the previous limits on free quark production in electromagnetic interactions by 2 orders of magnitude.

A SEARCH FOR NEUTRAL HEAVY LEPTONS

Abstract In e + e − annihilations at SPEAR we have searched for narrow neutral resonances in the eπ and μπ channels for masses between 0.5 GeV/ c 2 and 1.5 GeV/ c 2 . No evidence for such states has been found. Under standard theoretical assumptions for production cross sections and decay branching ratios of heavy leptons a lower limit of 1.2 GeV/ c 2 can be set on the mass.