SEARCH FOR T-VIOLATION IN B DECAYS

搜索 B 衰变中的 T 破坏

• 批准号: 07454057
• 负责人: KUNO Yoshitaka
• 金额: $ 3.46万
• 依托单位: National Laboratory for High Energy Physics
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07454057/
• 关键词: 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

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.

我们研究了在B介子衰变，特别是B介子衰变中寻找时间反转不变性(T违犯)的可能性。为了寻找T破坏，自旋极化分量(格子P_T)垂直于由D介子和tau动量矢量定义的衰变强度。如果P_T不为零，则蕴含T-违例。对于K衰变也有类似的方法，但B衰变比K衰变有一些优势。它们中的一些来自于BMeson和tau比KMeson和Muon更重。例如，在多个希格斯双重态模型中，带电的希格斯通过它们的质量与费米子耦合。这意味着B衰变的预期效应比K衰变大约100倍。在这项研究中，我们研究了如何识别处于末态的两个中微子中存在潜在问题的事件。这使得重建这些事件变得困难。我们考虑了两种方法。一种是用硅微带探测器(SSD)测量tau衰变顶点。它需要100微米的位置分辨率。而且它必须足够薄，以减少多次散射效应。我们已经构建了100微米厚的SSD，其中300微米厚是正常的。我们已经测试过了。其次，我们试图重建在电子-正电子碰撞中成对产生的另一个B介子，例如在KEK计划的一个B工厂项目。一旦另一个B被重建，感兴趣的B将受到运动学约束。从这些方法中，我们估计大约有1000个事件可以预期，产生大约几个百分点的准确率。