| Project/Area Number |
08044100
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Joint Research |
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| Research Field |
素粒子・核・宇宙線
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| Research Institution | High Energy Accelerator Research Organization, Institute for Particle and Nuclear Studies |
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Principal Investigator |
IMAZATO Jun High Energy Accelerator Research Organization (KEK), Institute for Particle and Nuclear Studies (IPNS), Professor, 素粒子原子核研究所, 教授 (40107686)
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| Co-Investigator(Kenkyū-buntansha) |
HASHINOFF M. University of British Columbia, Department of Physics, Professor, 教授
KUDENKO Y.G. Institute for Nuclear Research of the Russian Academy of Sciences, Researcher, 原子核研究所, 上級研究員
ASANO Yuzo University of Tsukuba, Institute of Applied Physics, Professor, 物理工学系, 教授 (80100808)
KUNO Yoshitaka KEK,IPNS,Associate Professor, 素粒子原子核研究所, 助教授 (30170020)
杉本 章二郎 高エネルギー加速器研究機構, 素粒子原子核研究所, 教授 (20044753)
LOBASHEV V.M. Institute for Nuclear Research of the Russian Academy of Sciences, Professor
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| Project Period (FY) |
1996 – 1997
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| Keywords | T-violation / CP-violation / K_<mu3> decay / transverse polarization / stopped kaon / superconducting toroidal spectrometer / KEK-PS / CsI (TI) |
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| Research Abstract |
A Search for time-reversal invariance (T) violation, via a high precision measurement of the transverse muon polarization, P_T in the K^+*pi^0mu^+nu decay, was conducted by the E246 international collaboration at KEK-PS.A non-zero value of P_T would be clear evidence for T-violation. The spurious effect from final state interactions is small in this charged kaon decay. In addition, the standard model contribution to P_T is negligibly small. Hence P_T is very sensitive to mechanismes of CP-violation beyound the standard model. The multi-Higgs doublet or leptoquark and supersymmetric models are currently of interest.
The experiment used a stopped K^+ beam and a Superconducting Toroidal Spectromer. With stopped K^+ the entire decay kinematics region could be covered. Combined with the 30ﾟ rotational symmetry of the toroid almost all systematic errors were cancelled. The detector consisted of 1) an active target with 256 scintillating fibers and a ring counter system, 2) a pi^0 detector with 768 CsI (TI) crystals, 3) a muon tracking system with four wire chambers, 4) TOF counter system, and 5) muon polarimeters. P_T was measured as the clockwise/counterclockwise asymmetry of decay positrons in the polarimeter.
Data taking started in 1996. At an early stage of data taking, good detector performance was verified. The positron time spectra contained a very small level of time independent background. For pi^0 identification both two photon and single photon events could be analyzed. The data taken in 1996 and 1997 are under analysis. According to a preliminary result, the T-violating parameter Imxi is consistent with zero with a statistical accuracy of 2x10^<-2> superceding the previous limit from BNL-AGS.Systematic errors have been shown to be much smaller than the statistical ones from the experimental data.
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