M. Alston-Garnjost

Analysis of the observed anomaly in ππ s-wave scattering near KK̄ threshold

Abstract The character of the ππ s-wave scattering amplitude near 980 MeV is determined from the reactions π + p→‡ ++ π + π − and ‡ ++ K + K − at 7GeV/c.

Observation of an anomally in the π+π− system at 980 MeV

Abstract An anomaly at 980 MeV is seen in both the mass distribution and angular distribution of the π + π − system produced in the reaction π + p → Δ ++ π + π − at 7 GeV/ c . Experimental results for the related final states Δ ++ K + K − , Δ ++ π + π − π + π − and Δ ++ π + π − (neutrals) are presented.

Tests of models for quark and gluon fragmentation ine+e− annihilation at\(\sqrt s = 29 GeV\)

Three currently used fragmentation models are tested by studying the distribution of particles between jet axes in the 3-jet events ofe+e− annihilation, using data collected by the Time Projection Chamber at PEP. These three models — the Lund String model, the Webber Cluster model and an Independent Fragmentation model (IF) — each implement different Lorentz-frame structures for the fragmentation process of quarks and gluons into hadrons. The Lund model provides a good description of the data, while the IF model does not. The Webber model, which is untuned, does not describe the absolute particle densities between jets, but correctly predicts the ratios of those densities, which are less sensitive to the tuning.

Inclusive D*+- production in photon-photon collisions

Abstract The TPC/Two-Gamma Collaboration has measured the inclusive cross section for production of charmed D∗± mesons in photon-photon collisions. The reaction utilized was e+e-→e+e-D∗±X, with D∗±→DOπ+-, DO→K-+π ±, and either zero or one outgoing e± detected. The result, σ(e + e - → e + e - D ∗± X) = 74±26±19 pb , is in agreement with the quark parton mo del prediction for e+e- → e+e-c c , combined with a Lund model for the hadronization of the charmed quarks.

Energy dependence of inclusive distributions in pion-induced reactions☆

Abstract We present data on the inclusive distributions π + p → π ± + anything and π − p → π − + anything at momenta from 3.7 to 18.5 GeV/ c . Distributions are presented in the laboratory, center-of-mass and projectile systems, and the approach to scaling is discussed.

Prompt electron production ine+e− annihilations at 29 GeV

We have measured the inclusive prompt electron cross section over a wide momentum range (P>0.5 GeV/c) with the PEP-4 TPC detector. The semielectronic branching fractions of thec andb quarks are (9.1±0.9 (stat.)±1.3 (syst.))% and (11.0±1.8±1.0)%, respectively. Theb quark fragmentation function peaks at highz with 〈zb〉=0.74±0.05±0.03. The axial couplings to the neutral current areac=2.3±1.4±1.0 for thec quark andab=−2.0±1.9±0.5 for theb quark.

A2 mass spectrum in 7-GeV/c π+p interactions

Abstract The A 2 mass spectrum is studied in the reaction π + p→A 2 + p atZZ 7 GeV/ c in a hydrogen bubble chamber in order to investigate previously reported structure. We report on 1400 A 2 events with mass resolutions of 3.8, 6.7 and 9.2 MeV in the K + K 0 , 3π and ηπ + channels.

Spatial Resolution of the PEP-4 Time Projection Chamber

The spatial resolution and response of the segmented cathode pads of the PEP-4 TPC have been measured with data taken at 8.5 atmospheres of 80% Argon-20% Methane gas with a 4kG magnetic field. The dependence of the spatial resolution and pad response on drift distance and track-anode crossing angle is presented.

Measurement of Ionization Loss in the Relativistic Rise Region with the Time Projection Chamber

We present here some results obtained with the LBL Time Projection Chamber (TPC) regarding the particle identification by the measurement of the ionization losses in the relativistic rise region. This includes the method of calibration using 55Fe sources, the measurement of the resolution using cosmic rays, which shows an equivalent K-¿ separation of 4.8 standard deviations at 3.5 GeV/c, and the preliminary results obtained with multihadronic events from e+e- annihilations.

Inclusive γ and π0 production cross sections and energy fractions ine+e− annihilation at 29 GeV

Inclusive production cross sections for photons and π0s ine+e− annihilation at a center of mass energy of 29 GeV have been measured. The π0 production spectrum agrees with a corresponding measurement for π±. The ratio of the π0 inclusive rate to the average for π± is 0.92±0.14. The fractions of the total energy carried by photons and π0s are 0.244±0.016 and 0.217±0.033, respectively. The fraction of total energy carried by all stable hadrons, prompt leptons and photons is determined to be 0.938±0.045, leaving 0.062±0.045 for neutrinos.