R. Sugahara

TOPAZ barrel electromagnetic calorimeter at TRISTAN, KEK

Abstract A barrel electromagnetic calorimeter consisting of 4300 lead glass blocks has been constructed and operated in the TOPAZ electron-positron colliding experiment, at TRISTAN, KEK. Details of the apparatus, the readout system, the calibration procedure, and the stability monitoring system are presented. The performance of the detector studied with a test setup and that obtained in the initial experimental runs are discussed.

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.

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.

Inclusive Λ, Λ and Σ±(1385) production in 405 GeV/c pp interactions

We have investigated inclusive Λ, Λ and Σ±(1385) productions in 405 GeV/c pp interactions. The observed cross sections are σ(Λ)=4.05±0.39 mb, σ(Λ=0.63±0.17 mb, σ(Σ+(1385))=0.74±0.17 mb and σ(Λ−(1385))=0.56±0.17 mb. Λ production is dominant in a central region of ∣x∣≤0.4. The Λ/Λ production ratio at ∣x∣≈0 is found to be 1.2±0.5. The excess, about 0.2 mb, of σ(Λ+(1385)) over σ(Λ−(1385)) is most likely attributed to proton fragmentations (∣x∣≥0.4), and gives an evidence for scaling.

The interaction region of KEKB

Abstract An asymmetric-energy collider of 8 GeV electrons and 3.5 GeV positrons, KEKB, has been operating at KEK since 1998. On July 9, 2001 it achieved the highest record of luminosity, 4.5×10 33 cm −2 s −1 . This paper describes the interaction region (IR) extending about 8 m from the interaction point (IP) along each beam direction. The main machine components in the IR are focusing quadrupole magnets, compensation solenoids, and vacuum chambers, which are positioned on movable stages. They are designed to focus both beams into collisions with a finite angle crossing.

Measurement of the processes e+e−→e+e− and e+e−→γγ at s=52 GeV

Abstract Differential cross sections for the processes e + e − → e + e − (Bhabha scattering) and e + e − → γγ have been measured with the TOPAZ detector at s =52 GeV . The results agree with the predictions of quantum electrodynamics (QED). The lower limits for the QED cut-off parameters have been obtained to be Λ + ⩾115 GeV and Λ − ⩾236 GeV for Bhabha scattering, and Λ + ⩾94 GeV and Λ − ⩾59 GeV for the reaction e + e − → γγ .

Performance Test of the TOPAZ Barrel Calorimeter

A large-scale electromagnetic calorimeter comprising 4300 lead glass Cherenkov counters has been constructed for the TOPAZ detector at the TRISTAN e+e- collider. Various beam tests have been performed to study the basic properties. The data were compared with simulated data based on the EGS4 code. In this report, the results of beam tests and a comparison to simulated data are described.

Charge asymmetry measurement in e+e−→μ+μ− and τ+τ− reactions at s=52 GeV and 55 GeV

Abstract The reactions e + e − → μ + μ − and τ + τ − were measured at s =52 GeV and 55 GeV by using the TOPAZ detector at TRISTAN. For the combined data, the observed charge asymmetry is −0.29±0.13 and the total cross section is 27.9±3.0 (stat.)±0.8 (syst.) pb for μ + μ − production, and those for τ + τ − production are −0.20±0.14 and 35.7±4.3 (stat.)±2.4 (syst.)pb, respectively. These values are consistent with predictions by the standard model of electroweak interactions.

Measurement of the Processes

Abstract Differential cross sections for the processes e + e − → e + e − (Bhabha scattering) and e + e − → γγ have been measured with the TOPAZ detector at s =52 GeV . The results agree with the predictions of quantum electrodynamics (QED). The lower limits for the QED cut-off parameters have been obtained to be Λ + ⩾115 GeV and Λ − ⩾236 GeV for Bhabha scattering, and Λ + ⩾94 GeV and Λ − ⩾59 GeV for the reaction e + e − → γγ .

e^+ e^- \to e^+ e^-

Abstract We have observed high mass resonances with mass above 1.5 GeV in pp interactions at 405 GeV/ c . We obtain cross sections 13.2 ± 2.9, 5.1 ± 2.0, 2.5 ± 1.5 and 0.27 ± 0.18 mb for ϱ 0 , f, g 0 , and h meson production, respectively. The invariant x and p T 2 distributions for produced resonances are analysed. A relative comparison of the average 〈 p T 〉 distribution as a function of resonance masses with that for μ + μ − pair production shows remarkable similarity.