SEARCH FOR T-VIOLATION IN B DECAYS

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We have studied the possibility to search for a violation of the time-reversal invariance (T violation) in B meson decays, in particular B tauonic decays. In order to search for T-violation, the spin polarization component (celled P_T) that is normal to the decay plance defined by the D meson and tau momentum vectors. If P_T is not zero, it implies T-violation. Similar approaches have been done for K decays, but there are some advantages for B decays over K decays. Some of them have come from that Bmeson and tau are heavier than Kmeson and muon. For instance, in multiple Higgs doublet models, charged Higgs are coupled to the fermions with their mass. It implies that the expected effect is larger in B decays by about a factor of 100 over in K decays. In this research, we have studied how we can identify the events, where potential problems exist in two neutrinos in the final state. It makes it hard to reconstruct the events. We have considered two methods. One is to measure tau decay vertex by silicon micro strip detector (SSD). It needs a position resolution of 100 microns. And it has to be thin enough to reduce multiple scattering effects. We have constructed 100 micron thick SSD,where 300 micron thick is normal. We have tested it. Second, we have tried to reconstruct the other Bmeson which is pair-produced in electron-positron collision such as a B factory project planned at KEK.Once the other B is reconstructed, the B of interest will be kinematically constrained. From these methods, we have estimated that about thousand events can be expected, yielding about a few percent accuracy.