Search for New Physics and the precision determination of the CKM matrix element |Vub| with the Belle II experiment

新物理学的探索与CKM矩阵元的精确测定|Vub|

• 批准号: 316996433
• 负责人: Professor Dr. Florian Bernlochner
• 金额: --
• 依托单位: Physikalisches Institut
• 依托单位国家: 德国
• 项目类别: Independent Junior Research Groups
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/316996433?language=en
• 关键词: Search; New; Physics; precision; determination

Matter and interactions of elementary particles in nature are so far successfully described by the Standard Model of particle physics. Albeit this success of the Standard Model, a range of physical phenomena observed in nature cannot be explained and a prominent example is the overabundance of matter over anti-matter in the universe. At the end of the year 2018 the super flavour factory experiment Belle II will start to record large samples of B-meson decays. The precision study of B-mesons is interesting as their decay allows for measuring the size of Charge-Parity violation and thus probe the matter and anti-matter asymmetry in particle decays. The size of Charge-Parity violation cannot be determined by a single measurement, but by the combination of several precision observables and any disagreement would be a strong indication for new physics processes beyond the Standard Model. The goal of this proposal is to carry out a precision measurement of the CKM matrix element Vub, whose absolute value is one of the important constraints in the extraction of the size of Charge-Parity violation. Experimentally Vub can be measured by studying semileptonic B-meson decays obtained by studying exclusive or inclusive hadronic final states. There is a long-standing tension between both approaches with a statistical significance of 3.4 standard deviations. One possible reason for this tension is the use of model functions to describe the b-quark motion inside the B-meson in state-of-the-art determinations using inclusive decays. To eliminate this possibility, this application proposes a coherent strategy how this functional form can be extracted simultaneously with Vub in a global analysis of measured kinematic distributions of radiative and semileptonic B-meson decays measured with the Belle II experiment. As part of the preparatory work and to establish the necessary experimental techniques a first analysis using Belle data will be carried out. The direct experimental determination of the functional form of the b-quark motion inside the B-meson will remove the model assumptions made in the state-of-the-art inclusive Vub measurements which in turn will help to shed light on the observed differences between inclusive and exclusive Vub measurements. In addition the shape function can be used to search for new physics contributions in radiative decays in a model independent way.

迄今为止，粒子物理学的标准模型成功地描述了自然界中的物质和基本粒子的相互作用。尽管标准模型取得了成功，但在自然界中观察到的一系列物理现象无法解释，一个突出的例子是宇宙中物质相对于反物质的过剩。在2018年底，超级香料工厂实验贝儿II将开始记录B介子衰变的大样本。B介子的精确研究是有趣的，因为它们的衰变允许测量电荷宇称破坏的大小，从而探测粒子衰变中的物质和反物质不对称性。电荷-宇称破坏的大小不能由一次测量确定，而是由几个精确观测值的组合来确定，任何不一致都将是超越标准模型的新物理过程的强烈迹象。该建议的目标是进行CKM矩阵元素Vub的精确测量，其绝对值是提取电荷奇偶违反的大小的重要约束之一。在实验上，Vub可以通过研究半轻子B介子衰变来测量，而B介子衰变是通过研究排斥或包容强子末态来获得的。两种方法之间存在长期的紧张关系，统计学显著性为3.4标准差。这种紧张的一个可能原因是使用模型函数来描述B-介子内部的B-夸克运动，这是最先进的使用包容性衰变的测定方法。为了消除这种可能性，本申请提出了一个连贯的策略，如何这个功能的形式可以同时提取与Vub在全球分析测量的辐射和半轻子B介子衰变的运动学分布测量的贝儿II实验。作为准备工作的一部分，为了建立必要的实验技术，将使用贝儿数据进行第一次分析。直接实验确定B介子内部b夸克运动的函数形式将消除最先进的包容性Vub测量中的模型假设，这反过来将有助于揭示包容性和排他性Vub测量之间观察到的差异。此外，形状函数还可以独立于模型地用于寻找辐射衰变中新的物理贡献。