C.R. Mindas

Apparatus for a search for T-violating muon polarization in stopped-kaon decays

Abstract The detector built at KEK to search for T-violating transverse muon polarization in K + → π 0 μ + ν μ ( K μ 3 ) decay of stopped kaons is described. Sensitivity to the transverse polarization component is obtained from reconstruction of the decay plane by tracking the μ+ through a toroidal spectrometer and detecting the π0 in a segmented CsI(Tl) photon calorimeter. The muon polarization was obtained from the decay positron asymmetry of muons stopped in a polarimeter. The detector included features which minimized systematic errors while maintaining high acceptance.

Measurement of Γ(Kμ3)/Γ(Ke3) ratio using stopped positive kaons

Abstract The ratio of the K + → π 0 μ + ν ( K μ 3 + ) and K + → π 0 e + ν ( K e 3 + ) decay widths, Γ ( K μ 3 )/ Γ ( K e 3 ), has been measured with stopped positive kaons. K μ 3 + and K e 3 + samples containing 2.4×10 4 and 4.0×10 4 events, respectively, were analyzed. The Γ ( K μ 3 )/ Γ ( K e 3 ) ratio was obtained to be 0.671±0.007(stat.)±0.008(syst.) calculating the detector acceptance by a Monte Carlo simulation. The coefficient of the q 2 dependent term of the f 0 form factor was also determined to be λ 0 =0.019±0.005(stat.)±0.004(syst.) with the assumption of μ – e universality in K l 3 + decay. The agreement of our result with the λ 0 value obtained from K μ 3 + Dalitz plot analyses supports the validity of the μ – e universality.

The Cherenkov correlated timing detector: beam test results from quartz and acrylic bars

Abstract Several prototypes of a Cherenkov correlated timing (CCT) detector have been tested at the KEK-PS test beam line. We describe the results for Cherenkov light yields and timing characteristics from quartz and acrylic bar prototypes. A Cherenkov angle resolution is found to be 15 mrad at a propagation distance of 100 cm with a 2 cm thick quartz bar prototype.

Test of exotic scalar and tensor interactions in K(e3) decay using stopped positive kaons

The form factors of the decay K+ → π0e+νe (Ke3) have been determined from the comparison of the experimental and Monte Carlo Dalitz distributions containing about 105Ke3 events. The following values of the parameters were obtained: λ+=0.0278±0.0017 (stat.)±0.0015 (syst.), |fS/f+(0)|=0.0040±0.0160 (stat.)±0.0067 (syst.), and |fT/f+(0)|=0.019±0.080 (stat.)±0.038 (syst.). Both scalar fS and tensor fT form factors are consistent with the Standard Model predictions of zero values.

The Cherenkov correlated timing detector: materials, geometry and timing constraints

Abstract The key parameters of Cherenkov correlated timing (CCT) detectors are discussed. Measurements of radiator geometry, optical properties of radiator and coupling materials, and photon detector timing performance are presented.

Detection of internally reflected Cherenkov light, results from the BELLE DIRC prototype

Abstract The DIRC (Detector of Internally Reflected Cherenkov light) is a new type of ring imaging Cherenkov detector which utilizes precisely machined quartz bars as Cherenkov radiators. Bar quality is determined by both laser and cosmic ray measurements. The Cherenkov photons are transported several meters along the bar until they reach the detector cavity where they are proximity focussed on an array of conventional photomultiplier tubes. Results from a prototype device comprising a 2 × 4 × 240 cm 3 quartz bar read by an array of 480 PMTs are presented. Sample images, which are the first observed in this type of detector, are also shown. Measurements of the light yield (approximately 20 photoelectrons per image) and the angular resolution, which are both in good agreement with Monte Carlo predictions, are shown to lie well within the expected operating tolerances of the DIRC.

A 32-CHANNEL WAVEFORM SAMPLING FASTBUS MODULE WITH LOCAL DSP PROCESSING

Abstract A 32-channel FASTBUS module that uses switched-capacitor arrays to sample and store input waveforms at rates up to 30 MHz is described. The captured data are digitized using commercial 12-bit analog-to-digital converters and are routed to an array of dual port memories. The data in the dual port memories can be readout directly over the FASTBUS backplane or can be subjected to further processing by a digital signal processor mounted on the FASTBUS auxiliary card.

New limit on T-violating parameters in kaon decays

A search for a T-violating transverse muon polarization (PT ) inK + → πμν decay was carried out in the experiment E246 at the KEK-PS. The Standard model (SM) predicts vanishing value of the polarization (< 10−7), so an observation of non-zero PT at the current experimental sensitivity level would be a definite signature of new physics beyond SM. The preliminary result of the analysis of the 1996-1998 data is presented here: PT = (−3.3±3.7(stat)±0.9(syst))×10−3, which corresponds to the T-violation parameter Im(ξ) = (−0.9 ± 1.2(stat) ± 0.3(syst)) × 10−2. There is no evidence for T-violation in Kμ3 at the current level of sensitivity.

A FAST DSP-BASED CALORIMETER HIT SCANNING SYSTEM

Abstract A custom made digital signal processor (DSP) based system has been developed to scan calorimeter hits read by a 32-channel FASTBUS waveform recorder board. The scanner system identifies hit calorimeter elements by surveying their discriminated outputs. This information is used to generate a list of addresses, which guides the read-out process. The system is described and measurements of the scan times are given.