T. Toyama

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 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.

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

Study of a drift chamber filled with a helium-ethane mixture

D~{*\pm}

Cross sections and charge asymmetries for e+e−→μ+μ− and e+e−→τ+τ−reactions at s=52−61.4 GeV

production cross section in a two-photon collision at the TRISTAN

Acceleration of the polarized proton beam at the KEK 12 GeV ps

e~+e~-

Test of phototube bases for high counting rates

collider. The mean

Cross-sections and charge asymmetries for e+ e- ---> mu+ mu- and e+ e- ---> tau+ tau- reactions at s**(1/2) = 52-GeV - 61.4-GeV

\sqrt{s}