A Study of Heavy Flavor Physics in the Lepton Sector

轻子领域的重味物理研究

• 批准号: 12440061
• 负责人: SUZUKI Shiro
• 金额: $ 5.06万
• 依托单位: Yokkaichi University (2001-2002)Nagoya University (2000)
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12440061/
• 关键词: CP; T violation; heavy flavor; lepton; rare decays; electric dipole moment; standard model; 電気二重極; タウレプトン; CP非保存; 標準理論

Facility of making high statistics simulation of production and decays of τ lepton pairs and rare decays of b quark, and skimming these samples from experimental data, are established in Nagoya University. Nagoya University takes responsibility of managing skimmed data of τ lepton events in the Belle collaboration. Those samples are opened to Belle collaborators through network "hepnet-J".Physics analyses were carried out in two stages. One were processes from which sizeable results were expected with rather low statistics (order of 10^<6-7>) such as CP/T violation in τ pair production, electric dipole moment (EDM) of τ, Cp violation in τ decays, a search for lepton flavor violation in τ decays. Others were processes we needed to accumulate high statistics, such as precision measurement of hadron mass spectrum in τ decay final states, and FCNC rare decay of b-quark associated with leptons.CP/T asymmetry in τ pair production indicates EDM of τ. We obtained new upper limit of τ EDM, one order of magnitude smaller than the existing ones, using τ decay modes to eμ, eπ, μπ, eρ, μρ, πρ, ππ, ρρ. Decay angular distribution of τ→ππ^0ν satisfied CP symmetry within a measurement limit. Lepton flavor violation was examined in the search for τ→μγ process. We have got smaller upper limit than the present best value, and analysis is in progress aiming to renew the limit by order of magnitude.As for the FCNC decay b → sll, we searched exclusive process of B → K(*)e^+e^- and B → K(*)μ^+μ^-, and first obtained sizeable decay branching fraction of B → Kl^+l^-, for which only upper limit had been obtained. Accumulating strange hadronic states we also obtained sizeable branching fraction of inclusive b → sll process.Those results were presented in journals and several international conferences like LP01, ICHEP00, ICHEP02, and heavy flavor workshop.

名古屋大学建立了对 τ 轻子对的产生和衰变以及 b 夸克的稀有衰变进行高度统计模拟，并从实验数据中撇取这些样本的设施。名古屋大学负责管理 Belle 合作中 τ 轻子事件的略读数据。这些样本通过网络“hepnet-J”向 Belle 合作者开放。物理分析分两个阶段进行。一种是通过相当低的统计量（10^<6-7> 的量级）预期获得相当大结果的过程，例如 τ 对产生中的 CP/T 违规、τ 的电偶极矩 (EDM)、τ 衰变中的 Cp 违规、在 τ 衰变中寻找轻子风味违规。其他是我们需要积累高统计数据的过程，例如 τ 衰变最终状态下强子质谱的精确测量，以及与轻子相关的 b 夸克的 FCNC 稀有衰变。 τ 对产生中的 CP/T 不对称性表明 τ 的 EDM。利用 τ 衰减模式对 eμ、eπ、μπ、eρ、μρ、πρ、ππ、ρρ 进行计算，得到了新的 τ EDM 上限，比现有上限小一个数量级。 τ→ππ^0ν 的衰变角分布在测量极限内满足 CP 对称性。在寻找 τ→μγ 过程时检查了轻子风味违规。我们已经得到了比目前最佳值更小的上限，正在进行分析，旨在按数量级更新极限。对于 FCNC 衰变 b → sll，我们搜索了 B → K(*)e^+e^- 和 B → K(*)μ^+μ^- 的排他过程，并首先获得了相当大的 B → Kl^+l^- 衰变分支分数，但仅获得了上限。通过积累奇怪的强子态，我们还获得了包含 b → sll 过程的相当大的分支分数。这些结果发表在期刊和一些国际会议上，如 LP01、ICHEP00、ICHEP02 和重口味研讨会。

项目成果

K.Abe et al.: "Observation of the Decay B→Kl^+l^-"Phys.Rev.Letters. 88. 021801 (2002)

K.Abe 等人：“衰变 B→Kl^+l^- 的观察”Phys.Rev.Letters 88. 021801 (2002)

K.Abe et al.: "Study of the Electroweak Penguin Decay B→K^<(*)>l^+l^-"BELLE-CONF. 0241. (2002)

K.Abe 等人：“电弱企鹅衰变 B→K^<(*)>l^+l^-”BELLE-CONF 0241 的研究。(2002)

K.Abe et al.: "Search for τ→μγ decay at Belle"BELLE-CONF. 0018. (2001)

K.Abe 等人：“寻找 Belle 的 τ→μγ 衰变”BELLE-CONF. (2001)

K.Abe et al.: "Evidence for the Electroweak Penguin Decay B → Xsl^+l^-"BFLLE-CONF. 0110. (2001)

K.Abe 等人：“电弱企鹅衰变 B → Xsl^+l^-”BFLLE-CONF 0110 的证据。(2001)

K. Abe et al.: "Search for τ→μγ decay at Belle"BELLE-CONF. 0118. (2001)

K. Abe 等人：“寻找 Belle 的 τ→μγ 衰变”BELLE-CONF. (2001)