B. Howell

Measurement of the inclusive cross section of jets in γγ interactions at TRISTAN

Abstract We have investigated the properties of jet production in almost real γγ collisions at √s=58 GeV with the TOPAZ detector at the TRISTAN e+e− collider. The data were analyzed with a jet-clustering method based on a cone algorithm. The jet rate shows evidence for a hard scattering effect of the hadronic constituents of a photon (resolved photon processes). We have also observed a substantial energy flow in the small-angle region, which is additional evidence for resolved photon processes. We present the transverse momentum dependence of the inclusive jet and two-jet cross sections and compare them with different model predictions.

Measurement of inclusive particle spectra and test of MLLA prediction in e+e− annihilation at s=58Gev

Abstract Inclusive momentum spectra are measured for all charged particles and for each of π ± , K ± , K 0 K 0 , and p p in hadronic events produced via e + e − annihilation at s =58 Gev . The measured spectra are compared with QCD predictions based on the modified leading log approximation (MLLA). The MLLA model reproduces the measured spectra well. The energy dependence of the peak positions of the spectra is studied by comparing the measurements with those at other energies. The energy dependence is also well described by the MLLA model.

Search for SUSY Particles in e+ e- Annihilation at Tristan

Abstract The TOPAZ detector has accumulated about 11 pb−1 of data in the energy range s =52−57 GeV . Charged supersymmetric particles have been searched for. Assuming the photino to be massless, we place limits on the chargino of m χ GeV , on the scalar muon, tau, and quark of m μ GeV , m τ GeV , and m q GeV . The scalar electron can be excluded up to a mass of ∼ 28 GeV. Other cases are examined.

Measurement of the D ± Cross Section using a Soft-Pion Analysis in Two-Photon Processes

Abstract The differential cross section of dσ(e + e − → e + e − D ∗± X) dP T was measured using a soft-pion analysis D ∗± → π s ± D 0 (D 0 ) at TRISTAN. The average s was 58.7 GeV and the integrated luminosity used in this analysis was 198 pb − , respectively.

Measurement of the photon structure function F2γ and jet production at TRISTAN

Abstract We have measured the photon structure function F2γ in the reaction e+e− → e+e− hadrons for average Q2 values from 5.1 to 338 GeV2 by using data collected by the TOPAZ detector at TRISTAN. The data have been corrected for detector effects and are compared with theoretical expectations based on QCD. The structure function F2γ increases as ln Q2, as expected. A sample of events with one or two distinct jets has been identified in the final state. Although two-jet events can be explained solely by the point-like perturbative part, one-jet events require a significant hadron-like part in addition.

Experimental study of b-quark jets in e+e− annihilation at TRISTAN

Abstract An experimental study of b-quark jets using high-pT electrons was carried out at √s=58 GeV with the TOPAZ detector at the e+e− collider TRISTAN at KEK. The forward-backward charge asymmetry of the b-quark was obtained to be A b b =−0.55±0.27( stat. )±0.07( syst. ) , consistent with the standard model prediction. Also, such jet properties of the b-quark as the average charged multiplicity and the rapidity of charged particles were analyzed. In order to purify the b-quark event samples in this analysis, only events with backward-going electrons or forward-going positrons were used. The energy dependence of these jet properties was studied by making comparisons with the results of the DELCO experiment at the PEP collider (√s=29 GeV) at SLAC.

Measurements of αs in e+e− annihilation at √s=53.3 GeV and 59.5 GeV

Abstract We studied the energy-energy correlation (EEC) and its asymmetry (AEEC) using e + e − hadronic annihilation events obtained at √ s =53.3 GeV and 59.5 GeV with the TOPAZ detector at the TRISTAN collider. We used a Monte Carlo simulation combined with the QCD matrix elements by Gottschalk and Shatz and the Lund string fragmentation model. By comparing the experimental data with simulated events, we determined the strong coupling constant α s at both energies. The results are 0.129±0.007 (stat) ±0.010 (syst) at √ s =53.3 GeV and 0.122±0.008 (stat) ±0.010 (syst) at 59.5 GeV.

Measurements of αs in e+e- annihilation at /TRISTAN

Abstract The strong coupling constant α s was determined from analyses of the thrust, heavy jet mass and, differential 2-jet rate, using e + e - hadronic events at s = 58 GeV with the TOPAZ detector at TRISTAN. The NLLjet Monte Carlo simulation (NLLjet) and analytic formulae based on resummation up to the next-to-leading logarithms combined with O ( α 2 s ) calculations were used to evaluate α s . The average α s values at Q 2 = (58 GeV) 2 from the analyses are α s = 0.125 ± 0.009 for NLLjet and α s = 0.132 ± 0.008 for the resummed analytic formulae.

Measurement of the D∗+ cross section in two-photon processes

We have measured the inclusive

Measurement of the total hadronic cross section and determination of γ-Z interference in e+e− annihilation

D~{*\pm}