SEARCH FOR T-VIOLATION IN B DECAYS

• Project/Area Number: 07454057
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 素粒子・核・宇宙線
• Research Institution: National Laboratory for High Energy Physics
• Principal Investigator: KUNO Yoshitaka National Laboratory for High Energy Physics, ASS.PROF., 物理研究部, 助教授 (30170020)
• Co-Investigator(Kenkyū-buntansha): NAKANO Takashi RCNP OSAKA,ASS.PROF., 核物理研究センター, 助教授 (80212091) ; OZAKI Hitoshi National Laboratory for High Energy Physics, ASS.PROF., 物理研究部, 助手 (10177214) ; OKADA Yasuhiro National Laboratory for High Energy Physics, ASS.PROF., 物理研究部, 助教授 (20212334)
• Project Period (FY): 1995 – 1996
• Project Status: Completed (Fiscal Year 1996)
• Budget Amount: ¥5,400,000 (Direct Cost: ¥5,400,000); Fiscal Year 1996: ¥2,600,000 (Direct Cost: ¥2,600,000); Fiscal Year 1995: ¥2,800,000 (Direct Cost: ¥2,800,000)
• Keywords: B MESONS / T-VLOLATION / TAU / NEVTRINO / SIUCOP DETECTOR / D MESON / HIGGS MODEL / SPIN POLARIZATION / B中間子崩壊 / 時間反転対称性の破れ / タウ粒子 / シリコン・ストリップ測定器 / 事象構成 / τ粒子 / D^*中間子

Research Abstract

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.