Makoto Tomoto

Time-of-propagation Cherenkov counter for particle identification

Abstract We describe here a new concept of a Cherenkov detector for particle identification by means of measuring the Time-of-Propagation (TOP) of Cherenkov photons.

Development of a 24-anode linear-array fine-mesh PMT with 85% photoelectron detection efficiency and 100 ps TTS at

By shortening the distance between the photocathode and the first dynode to 1 mm and using a finer mesh size of 2500 lines/in. with , a 24 anode linear-array of fine-mesh photomultiplier tube has produced a clear single-photon peak in its pulse-height distribution under a strong magnetic field of , and provided of transit time spread (TTS) and 85% of photoelectron detection efficiency.

A high-resolution cylindrical drift chamber for the KEK B-factory

The Central Drift Chamber of the BELLE detector at the KEK B-factory is a cylindrical wire chamber device that uses a helium-based gas and aluminum field wires and is situated in a 1.5 T magnetic field. The transverse momentum resolution for charged tracks with 1.0 GeV/c transverse momentum is 0.35%. This paper describes the chambers configuration and performance.

Study of a dE/dx measurement and the gas-gain saturation by a prototype drift chamber for the BELLE-CDC

Abstract We studied the performance of a d E d x measurement using an actual real-size prototype of the Central Drift Chamber for the KEK B-Factory. The observed dependences on the track incident angles showed a gas-gain saturation effect due to the space-charge. This gas-gain saturation caused the chamber response to d E d x of the incident particles to be weaker. We measured gas-gain saturation as a function of the line-charge density on a sense wire made by an incident charged particle, and observed that the line-charge density dominantly determined the gas-gain saturation.

Charged particle multiplicities of quark and gluon jets in e+ e- annihilation at TRISTAN

Abstract Charged-particle multiplicity was studied in e+e− annihilation at s = 57.8 GeV using the TOPAZ detector at TRISTAN. The average multiplicity was 〈nch〉 = 17.64± 0.05(stat.) ± 0.41(syst.). It was found that the multiplicity depends on the thrust (T) of an event. From extrapolating this relation to T = 2 3 , the multiplicity for three-fold symmetric events was estimated to be 〈n ch 〉 T = 2 3 = 23.50 −1.45 +1.25 . From this, the multiplicity ratio between gluon- and quark-jet was estimated to be r g q = 1.46 −0.13 +0.09 without any possible bias from jet clustering.

Test of charge-to-time conversion and multi-hit TDC technique for the BELLE CDC readout

We tested a new CDC readout scheme utilizing a Charge-to-Time conversion (QTC) technique and multi-hit TDC to record both time and charge information. The new scheme is planned to be used in the BELLE experiment at the KEK B-Factory. We built a prototype Shaper/QTC board and examined the performance with a beam test. This new scheme worked successfully. We obtained the same spatial and dEdx resolutions as those using an ordinary TDC and ADC readout scheme.

A study of single photon production in e+e− collisions at s=58 GeV with the TOPAZ detector at TRISTAN

Abstract We report a study of single photon production in e+e− collisions at s =58 GeV with the TOPAZ detector at TRISTAN. From data corresponding to an integrated luminosity of 213 pb−1, 5 single photon candidates remained after event selection, which can be compared with the expected 3.1 ν ν γ and 2.8 background events. These results exclude the selectron mass below 47.2 GeV at the 90% confidence level, if e L and e R are mass-degenerate and the photino is massless. When combined with results from other experiments, this limit improves to 75.0 GeV.

Magnetic field mapping of the Belle solenoid

The mapping of the magnetic field of the Belle detectors large superconducting solenoid is described. The mapping was done with the accelerator magnets located inside the Belle solenoid excited to their nominal field values. To cope with geometrical constraints, we developed a novel moving mechanism for the field probes that uses an ultrasonic motor located in the strong magnetic field.

Measurement of the cross-section and forward-backward charge asymmetry for the b and c-quark in \(e^+e^-\) annihilation with inclusive muons at \(\sqrt{s} = 58\) GeV

Abstract. We have studied inclusive muon events using all the data collected by the TOPAZ detector at

Z-trigger system with the BELLE Central Drift Chamber

\sqrt{s}=58