Y. Teramoto

Muon identification in the Belle experiment at KEKB

Abstract This paper describes the muon identification method and its performance in the Belle experiment at KEKB. Muon and hadron likelihood are calculated for each track using its range and transverse scattering in the KL-and-muon detector (KLM). We apply a cut on the normalized muon likelihood L μ to identify the track as a muon. Above the detection threshold of 0.6 GeV /c , the measured muon detection efficiency and pion fake rate are approximately constant for momenta greater than 1.0 and 1.5 GeV /c , respectively. Between 1.0 and 3.0 GeV /c , the averaged muon detection efficiency is 89% and the pion fake rate per track is 1.4% over the KLM acceptance, using the standard selection criterion L μ >0.9 .

The KL/μ detector subsystem for the BELLE experiment at the KEK B-factory

Abstract The KL and muon detection subsystem (KLM) of the BELLE experiment at the KEK-B asymmetric B-factory is described. The system consists of glass-electrode resistive plate counters installed within the segmented flux return iron of the BELLE superconducting solenoid. The design and construction of the detectors, including the gas distribution system and readout electronics, are described in detail. The operating characteristics and performance with cosmic rays and e+e− collision data are presented.

Measurement of R and search for new heavy quarks in e+e- annihilation at 50 and 52 GeV centre-of-mass energies

Abstract The total cross section for the process of the e+e- annihilation into hadrons has been measured at the centre-of-mass energies of 50 GeV and 52 GeV and a search has been made for new heavy quarks. The ratios R = σ(e+e- → hadrons)/σpoint(e+e- → μ+μ-) obtained are 4.4±0.5 at 50 GeV and 4.7±0.3 at 52 GeV, respectively. An additional systematic uncertainty is 10%. From the event shape analysis we found no evidence for a new quark with charge 2 3 e .

Study of the effect of water vapor on a resistive plate chamber with glass electrodes

Abstract We studied the effects of water vapor on the efficiencies of resistive plate chambers with glass electrodes, operated in the streamer mode. With moisture in the chamber gas that has freon as a component (water vapor ∼1000 ppm ), a decrease in the efficiency (∼20%) has been observed after operating for a period of several weeks to a few months. From our study, the cause of the efficiency decrease was identified as a change on the cathode surface. In addition, a recovery method was found: flushing for 1 day with argon bubbled through water containing ⩾3% ammonia, followed by a few weeks of training with dry gas.

Cosmic-ray test of the installed endcap RPC modules in BELLE detector

In BELLE detector at KEKB, the resistive plate counter (RPC) modules were constructed for the muon trigger and K/sub L//sup 0/ detection. The endcap quadrant consisting of 14 superlayer RPC modules alternating with 47 mm thick iron plates and the 112 endcap modules have been installed in BELLE detector. We study on the tracking performance of the installed endcap RPC modules using by cosmic-ray test for the whole BELLE detector system.

RPC systems for BELLE detector at KEKB

Abstract We constructed glass RPC modules for detecting K L and muon in BELLE experiment. The modules have been installed in the instrumented iron yoke outside of the solenoid coil and cover about 2000 m 2 of detectors. We report the design and construction of the detectors, including the gas distribution and exhaust system, the HV system, the readout electronics and DAQ system. The performance with cosmic ray and the e + e − collision data are presented.

Search for the Top Quark in e+e- Annihilation at \(\sqrt{s}=50\) GeV: The First Result from the VENUS Detector at TRISTAN

A result of the search for the top quark in e + e - annihilation into hadrons at \(\sqrt{s}=50\) GeV is presented. The experiment has been perforrnxed using the VENUS detector at TRISTAN. No evidence has been found for the production of the top quark. From the study using the event shape of the multihadron events, the upper limit of the production cross section is found to be 16 pb at thcc 95% confidence level.

Detection of Muons, and K//sup 0/sub L// Mesons from e+e- collisions using the endcap RPC module in the Belle detector

The BELLE experiment at KEKB has collected beam collision data from 1 June through 4 August 1999, corresponding to an integrated luminosity of 25 pb -1 , and the data contain approximately 10,000 e + e - -> μ + μ - events and 50,000 hadronic events. Using those events, we study the performance of the endcap RPC modules in the BELLE detector. The study shows that the endcap RPC modules perform quite well in detecting muons and K 0 L mesons.

Observation of light from resistive plate chambers

Abstract Electrically induced signals and light emissions from Restrictive Plate Chamber (RPC) are simultaneously measured using a glass RPC with transparent high-voltage planes, operating in the streamer mode. With one exception, good correspondence is seen in between the electrical and optical signals in every aspect: signal shapes, pulse heights, timing and afterpulses. The one exception is a possible limiting effect observed on the optical signal pulse height for a given pulse height of electrically induced signal. Shapes of the signal visually observed by eye are also described.

The trigger system of mutron, a cosmic ray magnetic spectrometer

Abstract A large magnetic spectrometer for cosmic-ray studies has been built at Cosmic Ray Laboratory, University of Tokyo, which consists of two 400 t solid iron magnets, multiwire proportional chambers (MWPC), wire spark chambers and a calorimeter. In this paper the trigger system will be described whose geometrical acceptance is about 1300 cm 2 sr including the magnets. The trigger system consists of twenty large area MWPCs. The trigger selection is made up of the momentum selection, which excludes low momentum muons, and the particle-number selection limiting the number of particles hitting the trigger detectors simultaneously. This combination for trigger reduces the background level and improves the ratio of muons to background. The trigger rate is about 1.0 per minute in the usual operation.