| Budget Amount *help |
¥3,640,000 (Direct Cost: ¥2,800,000、Indirect Cost: ¥840,000)
Fiscal Year 2014: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
Fiscal Year 2013: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000)
Fiscal Year 2012: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
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| Outline of Final Research Achievements |
We measure the branching ratio of B->taunu using the full data sample collected at the Belle experiment. Events with B meson pairs are tagged by reconstructing one of the B mesons decaying into hadronic final states, and B->taunu candidates are detected in the recoil. We find evidence for B->taunu with a significance of 3.0 standard deviations. By combining with the result based on a tag of B meson pairs using semileptonic decays, the branching ratio is evaluated to be (0.96+-0.26)x10-4. A stringent constraint is obtained for the ratio of the vacuum expectation values and the charged Higgs mass in Type II of two Higgs doublet models.
To improve the precision on B->taunu, we have developed a new particle identification system. Optical performance of the quartz radiator, which is a main component of the system, has been measured to be sufficiently high. The method of gluing multiple quartz bars for obtaining a full size of about 2.7 meters has been established.
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