Y. Igarashi

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.

Test of exotic scalar and tensor couplings in K+→π0e+ν decay

Abstract The form factors of the decay K + → π 0 e + ν ( K e 3 + ) have been measured with stopped kaons. Axa0Dalitz plot containing 4.1×10 4 events was analyzed. A comparison of the observed Dalitz plot with a Monte Carlo simulation determined the ratio of the strengths of possible scalar and tensor couplings to that of the vector coupling, f S / f + (0)=−0.002±0.026(stat)±0.014(syst) and f T / f + (0)=−0.01±0.14(stat)±0.09(syst). These values are consistent with the standard model prediction of zero, and disagree with a previous experiment. The analysis also yielded the coefficient of the q 2 term in the vector form factor to be λ + =0.0278±0.0026(stat)±0.0030(syst).

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.

CsI(Tl) photon detector with PIN photodiode readout for a Kμ3 T-violation experiment

Abstract The π0 detector constructed for the T-violation search experiment E246 at KEK is described. It consists of 768 CsI(Tl) crystals with PIN photodiode readout. The crystals are assembled in a tight barrel with holes for muons entering the magnetic spectrometer. The design and performance of the calorimeter are presented. The average light yield of 11u2008000xa0p.e./MeV and average equivalent noise level of 63xa0keV (bench test) were obtained for the CsI(Tl) modules used in the calorimeter. The coherent noise was found to be about 11xa0keV per a module. A readout electronics has been specifically developed for the high counting rate environment of the experiment. A π0 invariant mass resolution of 9.9xa0MeV (σ) was obtained for the whole detector, including regions around the muon holes. A time resolution of 3.8xa0ns (rms) was achieved in the photon energy range of 10–200xa0MeV.

New Limit on the T-Violating Transverse Muon Polarization in K^+ ¿ pi^0mu^+nu Decays

A search for T-violating transverse muon polarization (P(T)) in the K+-->pi(0)mu(+)nu decay was performed using kaon decays at rest. A new improved value P(T)=-0.0017+/-0.0023(stat)+/-0.0011(syst) was obtained giving an upper limit |P(T)|<0.0050. The T-violation parameter was determined to be Imxi=-0.0053+/-0.0071(stat)+/-0.0036(syst) giving an upper limit |Imxi|<0.016.

A new limit of T-violating transverse muon polarization in the

A search for T-violating transverse muon polarization (P(T)) in the K+-->pi(0)mu(+)nu decay was performed using kaon decays at rest. A new improved value P(T)=-0.0017+/-0.0023(stat)+/-0.0011(syst) was obtained giving an upper limit |P(T)|<0.0050. The T-violation parameter was determined to be Imxi=-0.0053+/-0.0071(stat)+/-0.0036(syst) giving an upper limit |Imxi|<0.016.

K^{+}\to\pi^{0}\mu^{+} \nu

Abstract A dedicated local event builder for the KEK B-factory silicon microvertex detector is described. The event builder is a distributed system with a network of INMOS Transputers. INMOS B016 memory modules are used as an event buffer as well as an interface between the Transputer and the VME bus system (each B016 has one T801 Transputer). A circular buffer system is implemented in the software; this implementation is commonly used for memory management of the event builder and the front end digitizer. The Occam technique of this buffer management system is discussed in detail.

decay

Abstract The K + → π 0 μ + ν γ ( K μ 3 γ ) decay has been measured with stopped positive kaons at the KEK 12 GeV proton synchrotron. A K μ 3 γ sample containing 125 events was obtained. The partial branching ratio Br ( K μ 3 γ , E γ > 30 MeV , θ μ + γ > 20 ° ) was found to be [ 2.4 ± 0.5 ( stat ) ± 0.6 ( syst ) ] × 10 −5 , which is in good agreement with theoretical predictions.

Transputer based local event builder for the KEK B-factory silicon microvertex detector

A new result for the transverse mu^+ polarization, P_T, in the decay K^+ --> pi^0 mu^+ nu has been obtained in the KEK E246 experiment. Combined with our earlier result, P_T = (-1.12 +- 2.17(stat) +- 0.90(syst))x10^{-3} and Im(xi) = (-0.28 +- 0.69(stat) +- 0.30(syst))x10^{-2}, which are consistent with no T-violation.

Measurement of K+ ---> pi0 mu+ nu gamma decay using stopped kaons

Abstract High-precision magnetic-field mapping was performed for an experiment to search for a violation of time-reversal invariance in the K + → π 0 μ + ν μ decay at the KEK proton synchrotron. A commercially available three-dimensional Hall probe was used in conjunction with a specially designed mapping device and a goniometer system. Details concerning the measurement principle, calibration, actual measurements and analysis are described.