P. Baringer

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.

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.

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.

Measurement of the lifetime of hadrons containing the b-quark

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

First observation of inclusive ψ production in ψ decays

The branching ratio for inclusive ψ production in ψ(1S) decays is measured to be (0.11 ± 0.04 ± 0.02)%.

Charged K∗ production in e+e− annihilations at 29 GeV

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.

New results from Bhabha scattering 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.

Charged particle multiplicity distributions in e+e- annihilation at 29 GeV: a comparison with hadronic data

The charged particle multiplicity distributions for two-jet events ine+e− annihilation at 29 GeV have been measured using the High Resolution Spectrometer at PEP. A Poisson distribution describes the data for both the complete event and for the single jets. In addition, no correlation is observed between the multiplicities in the two jets of an event. For fixed values of the prong number of the complete event, the multiplicity sharing between the two jets is in good agreement with a binomial distribution. The rapidity gap distribution is exponential with a slope equal to the mean rapidity density. These observations, which are consistent with a picture of independent emission of single particles, are contrasted to the results from soft hadronic collisions and conclusions are drawn about the nature of clusters.

Inclusive η production in τ decays

Abstract We have searched for inclusive η production in τ decays using a data sample of 2553 events of e + e - →τ + τ - in the one-three topology. The data were obtained using the High Resolution Spectrometer at √ s =29 GeV. A 90% confidence level upper limit on the process τ ± →π ± ηX of 2.1% is found. Using τ decays to five charged particles limits of 0.5% on τ ± →π ± ηηX and 0.3% on τ ± →π ± π + π - ηX are also obtained.

Production and fragmentation of the D∗0 meson in e+e− annihilations at √s=29 GeV

Abstract Neutral D∗ meson production in e+e− annihilation at √s=29 GeV has been studied using the high resolution spectrometer. The decay of D∗0 into D0γ, where the D0 decays into K−π+, has been observed. The production cross section in units of the point cross section is 0.63±0.22 for fractional energy Z⩾0.5. The fragmentation function is compared with that of the D∗+ meson measured in the same experiment.