D.E. Wood

Rapidity Dependence of the Charged Particle Multiplicity Distributions in e+ e- Annihilation at 29-GeV

Abstract The charged particle multiplicity distribution for e+e− annihilations at s = 29 GeV has been measured using the High Resolution Spectrometer at PEP. The multiplicity distribution, expressed as a function of the mean, shows KNO scaling when compared to e+e− data at other energies. Multiplicity distributions for particles selected in different central rapidity spans are presented. All of these are well presented by the Negative binomial distribution. As the rapidity span is narrowed, the distributions become broader and approach a constant value of the parameter k.

Comparison of charged particle multiplicities in quark and gluon jets produced in e+e- annihilation at 29 GeV

The charged particle multiplicities of the quark and gluon jets in the three-fold symmetric e+e− → qqg events at √s = 29 GeV have been studied using the high resolution spectrometer at PEP. A value of 〈n〉g = 6.7−2.1+1.1±1.0 for gluon jet s with an energy of 9.7−2.0+1.5 GeV is measured. The ratio, 〈n〉g/〈n〉q, is 1.29−0.41+0.21±0.20, which i s significantly lower than the value of 94 naively expected from the ration of the gluon-to-quark color charges.

Neutral K*(890) and ρ0 meson production in e+e- annihilation at ;s=29GeV

Abstract The production of neutral K∗(890) and ρ0 mesons was studied in e+e− annihilation at s =29 GeV using the High Resolution Spectrometer at PEP. Differential cross sections are presented as a function of the scaled energy variable z and compared to π0 and K0 production. The measured multiplicities are 0.84±0.08 ϱ0 mesons and 0.57±0.09 K ∗0 (890) mesons per event for a meson momentum greater than 725 MeV/c. The ratios of vector meson to pseudoscalar meson production for (u,d), s and c quark are compared to predictions of the Lund model.

Charm Quark Production and Fragmentation in

Abstract The electroweak production asymmetry and the decay fragmentation function for e + e − → c c have been measured at s = 29 GeV using charged D ∗ production over the full kinematic range. The data were taken at PEP using the High Resolution Spectrometer. The measured asymmetry is −0.12 ± 0.08. The total production cross section in units of the point cross section corrected for initial state radiation is R D ∗ = 2.7 ± 0.9 .

e^+ e^-

Abstract Separate samples of charm quark and light quark (u, d, s) jets have been isolated in an experiment studying e + e − annihilations at s = 29 GeV . The results come from data corresponding to an integrated luminosity of 111 pb −1 collected by the High Resolution Spectrometer. Differences were observed in charged multiplicities, momentum distributions, and rapidity of the size expected from the different fragmentation functions and leading particle decay properties of the two samples.

Annihilation at 29-{GeV}

New results are given on Bhabha scattering at the center-of-mass energy of 29 GeV, based on a sample having an integrated luminosity of 165 pb/sup -1/ observed in the High Resolution Spectrometer (HRS) at the PEP colliding beam facility. The measured differential cross sections are used to evaluate Standard Model parameters, lower bound limts on QED cutoff parameters, and lower bound limits on composite model parameters. 10 refs., 1 fig., 3 tabs.

Comparison of light quark and charm quark fragmentation

Abstract The reaction e+e− → τ+τ− has been measured using the high resolution spectrometer at PEP. The angular distribution shows a forward-backward asymmetry of −(6.1±2.3±0.5)%, corresponding to an axial-vector coupling if gaτgae = 0.28 ±0.11± 0.03, in good agreement with the standard model of electroweak interactions. The measured cross section yields ifRττ = 1.10± 0.03±0.04, consistent with QED and giving QED cutoff parameters of Λ+>92 GeV and Λ−>246 GeV at 95% C.L.

New results from Bhabha scattering at 29 GeV

Abstract A search was made for e + e − →X 1 X 2 where X 1 consists of one or more light unobservable particles and X 2 decays promptly to a visible jet of particles. One event was found for an integrated luminosity of 176 pb −1 , a rate consistent with known backgrounds. This result places a significant constraint on a number of theoretical models.

Measurement of the reaction e+e− → τ+τ− at √s = 29 GeV

Inclusive production of charged particles has been studied in e+e− annihilation at ss=29 GeV using the high resolution spectrometer at PEP. Differential cross sections are presented in the range of scaled energy 0.1<z<1.0. The data for z<0.5 show the (1−z)2 behavior predicted by the dimensional counting rules. Comparisons are made with predictions of the Lund string model and the Webber cluster model.

Experimental limits on monojet production in e+e− annihilation at 29 GeV

Abstract A review of the performance of the barrel calorimeter system of the high resolution spectrometer (HRS) is given. The system has been in operation for several years at the PEP e + e − storage ring. The barrel calorimeter, consisting of Pb-scintillator sandwiches and proportional wire tubes with charge-division readout, measures the energies and production angles of electromagnetic showers and also provides time-of-flight for particles produced in e + e − collisions.