K. Neichi

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.

Performance of glass RPC operated in streamer mode with SF6 gas mixture

Abstract We have tested the performance of glass RPC operated in streamer mode with the gas mixture containing SF 6 instead of freon, HFC-134a. By using a small amount of SF 6 , we could operate the RPCs at a much lower high voltage with comparable performance to the HFC-134a mixture except for having a narrower efficiency plateau. The feasibility for using the SF 6 mixture is discussed.

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.

Optical study of the features of the streamer images in RPC

Abstract Optical images of the streamer from a Resistive Plate Chamber (RPC) are observed using a transparent high-voltage electrode in the operation of streamer mode. The optical images are measured using CCD camera system in mixture Ar/C4H10 with and without C2H2F4. Area of typical streamer image is approximately 12 mm 2 in both gas mixtures with its surrounding halo of 2– 4 mm in diameter. We also observed the quenching effect of C4H10 and C2H2F4 on the optical image in the chamber.

Neutron sensitivity of the endcap RPC modules in Belle detector

The primary purpose in the Belle experiment at the asymmetric-energy e/sup =/e/sup -/ collider at the High-Energy Accelerator Research Organization (KEK B factory) is the measurement of charge conjugation and parity (CP) violation in B meson decays. The K/sub L/ mesons and muons (KLM) detector was designed to identify K/sub L/s and muons in this experiment. Since October 2001, the luminosity in the KEK B accelerator has been remarkably improved. The data on B meson decay are successfully collected in the Belle detector. In contrast with the high luminosity operations of the accelerator, however, the high background rate leading to a lower detection efficiency has been observed in the endcap KLM detector. For present and future high luminosity operations, we have to identify the background source and consider the shielding. To identify the background source, the background data sampled from e/sup +/e/sup -//spl rarr//spl mu//sup +//spl mu//sup -/ events were investigated and the simulations of the sensitivity of the endcap KLM detector to neutrons and /spl gamma/s as the background sources were performed using the Geant4 simulation toolkit. The comparisons of the simulations with the experimental data are presented.

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.

Signal observation from a pulsed ionization chamber filled with tetramethyl germanium

Ionization signals from 207Bi conversion electrons were observed in a pulsed ionization chamber filled with purified tetramethylgermanium liquid. The free ion yield at zero field was measured as 0.57. The lifetimes of drifting electrons in the liquid were measured as 0.99, 3.99 and 4.32 µs for increasing purification cycles.

Performance of endcap RPC for the BELLE at KEK

The Resistive Plate Counters (RPC) has been provided for K/sub L//sup 0/ and muon detection in the BELLE experiment at KEK. The glass RPCs have been extensively tested using single cosmic-ray muons. We report on the performance of the endcap RPC with emphasis on detection efficiency and multiple hits of readout strips.

A study of non-flammable gas mixture for resistive plate counter

The RPC (resistive plate counter) has good time and position resolution. These factors make it an attractive candidate for trigger system at collider experiment. The standard gas mixtures (Ar+iso-C/sub 4/H/sub 10/+Freon) used in RPC are very flammable when leaked into air. In view of safety issue,we have studied non-flammable gas of Ar+CO/sub 2/+iso-C/sub 4/H/sub 10/+Freon as a function of ratio Ar:CO/sub 2/ allowed in non-flammable gas mixtures for the RPC with ABS electrodes. The basic performance of the various mixtures have been measured; singles (untriggered) count rate, detection efficiency and charge spectra versus operating voltage. We have found a set of non-flammable mixtures of the kind of Ar+CO/sub 2/+Freon contained less than /spl sim/8.4% of iso-C/sub 4/H/sub 10/ for K/sub L//muon counter of KEK B-factory at KEK.