D. Blockus

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.

Determination of ±s from a differential-jet-multiplicity distribution in e+e- collisions at ss =29 and 91 GeV

We measured the differential jet-multiplicity distribution in {ital e}{sup +}{ital e}{sup {minus}} annihilation with the Mark II detector. This distribution is compared with the second-order QCD prediction and {alpha}{sub {ital s}} is determined to be 0.123{plus minus}0.009{plus minus}0.005 at {radical}{ital s}{approx}{ital M}{sub {ital Z}} (at the SLAC Linear Collider) and 0.149{plus minus}0.002{plus minus}0.007 at {radical}{ital s}=29 GeV (at the SLAC storage ring PEP). The running of {alpha}{sub {ital s}} between these two center-of-mass energies is consistent with the QCD prediction.

Production cross section and electroweak asymmetry of D* and D mesons produced in e+e- annihilations at 29 GeV

Abstract The production of D * and D mesons has been studied in e + e − annihilations at √s = 29GeV. The data, corresponding to an integrated luminosity of 300 pb −1 , were obtained using the HRS detector at PEP. The cross section is measured to be R (D 0 + D + ) = 2.40±0.35 and we determine the electroweak asymmetry to be −9.9 ± 2.7%, which corresponds to an axial vector coupling constant product g e g c = 0.26 ± 0.07.

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.

Evidence for the decay τ+→π+ηντ

Abstract The inclusive production of η mesons in tau lepton decay has been studied using the High Resolution Spectrometer at the PEP e + e - facility. The data sample corresponds to an integrated luminosity of 300 pb −1 and the storage ring was operated at GeV. The η production appeaars to be only compatible with the decay τ + →π + η ν , which violates isospin and G -parity conservation. The branching ratio of 5.1±1.5% explains much of the current discrepancy between the one-prong topological branching ratio and the sum of the individual one-prong modes.

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}

Data collected with the High Resolution Spectrometer at PEP, corresponding to an integrated luminosity of 200 pb- 1 ofe+e annihilation at 29 GeV, were used to measure the mean hfetlme of hadrons containing the bottom quark. The hfetlme was determined using the impact parameter method on events containing a high-transverse-momentum electron The result, based on a sample of 301 events, is vB = 102~039042 ps, where the Indicated errors include both statistics and systematlcs In the context of the standard model, the lifetime of hadrons containing a bottom quark is determined by the electroweak coupling between the b and the c and u quarks. In the Kobayashi-Maskaw a scheme, the lifetime constrains the values of the matrix elements [ Vbc [ and ] Vbu [ [ 11. This letter presents a measurement of the lifetime of a mixture of hadrons containing the b-quark. The data sample consists of e+e---}bb annihilations at x/~=29 GeV, tagged by a high-PT electron coming from the semileptonic decay of the b-quark. Two different analysis techniques are used, but the quoted result is based on a maximum likelihood fit to the measured impact parameter distribution. A detailed description of the High Resolution Spectrometer can be found elsewhere [2]. For this analysis, the tracking system is essential. It consists

Comparison of light quark and charm quark fragmentation

Abstract We report a measurement of the charged K ∗ (892) production in e + e − annihilations at 29 GeV center-of-mass energy. The 300 pb −1 data sample used for this analysis is obtained with the High Resolution Spectrometer at the SLAC storage ring PEP. The total mean multiplicity is measured to be 〈n K ∗± (892) 〉=0.62±0.045±0.04 per hadronic event. Evidence is also given for the production of a charged K 2 ∗ (1430) tensor meson.