| Budget Amount *help |
¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 2003: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 2002: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 2001: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2000: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Research Abstract |
In this research project, we have studied the various properties of the tau lepton using the large amount of tau sample accumulated by the Belle detector in the electron-positron storage ring (KEKB) at KEK, Japan. The KEKB is the highest luminosity machine in the world, which recently achieves to the value of 1.0x10^<34>/cm^2/sec^2. Using the large amount of tau-lepton sample, the topics we have studied include;
1)Search for CP violation in tau decays (paper(1))
2)Search for Electric Dipole Moment of tau lepton (paper (4),(5));
3)Search for Lepton-Flavor-Violating decays (paper (2),(7),(8),(9));
4)Measurement of the 2π spectral function in the decay τ→ππν(paper (6)).
In the items 1) and 2), we carried out the search for the CP-violating phenomena in the tau-decay processes and in the tau-pair production. In 3), we have searched for the lepton-flavor-violation(LFV) decays for various decays modes including τ→μγ、μη、μμμ、μee. While LFV decays are not observed yet, we obtained new upper limits in the range 1-3x10^-7 at 90% confidence level using 80-130/fb data. These limits improve the previous results by one order of magnitude and provide the limit to the theoretical models based on SUSY and right-handed heavy neutrinos.
The 2pi spectral function in 4) is the important observable to improve the theoretical prediction of the muon anomalous magnetic moment (g-2), where the largest uncertainty exists in the hadronic vacuum polarization term. In order to make the precise measurement, careful checks are carried out on the various detector effects including pi0 efficiency, triggers and background. The preliminary results are presented in the paper (6) and we are now preparing a full paper for this research.
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