Precision Predictions for Flavour-Changing Neutral Current Decays

精确预测风味变化的中性电流衰变

• 批准号: 230799894
• 负责人: Professorin Dr. Gudrun Hiller
• 金额: --
• 依托单位: Lehrstuhl für Theoretische Physik IV
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2012
• 资助国家: 德国
• 起止时间: 2011-12-31 至 2016-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/230799894?language=en
• 关键词: Precision; Predictions; Flavour; Changing; Neutral

Quark decays which are induced by flavour-changing neutral currents (FCNCs) represent important tools to explore the borders of the Standard Model (SM) of particle physics. In the SM, these decays are suppressed by small mixing angles in the Cabibbo-Kobayashi-Maskawa (CKM) matrix and/or small Yukawa couplings of light quarks (GIM mechanism). In extensions of the SM, similar effective suppression mechanism are not necessarily realized, and therefore “new physics” (NP) signals can show up in decay rates and asymmetries. On the theoretical side, FCNC-processes at low energies are described in terms of effective Hamiltonian which allows to take into account contributions from the SM as well as from its possible extensions, including, for instance, effects from right-handed currents or new sources of CP-violation. To date, we have already observed a multitude of processes based on b-quark transitions to s-quark; first data have also become available for b to d decay modes, which are further suppressed by smaller CKM angles. The situation for FCNCs involving up-type quarks (u, c, t) is less advanced, partly because of the still stronger suppression of the corresponding decay rates. Within this project, we plan to perform a comprehensive theoretical study of various exclusive FCNC decays of hadrons containing b-quarks. Such decays are ideally suited to test the fundamental interactions in and beyond the SM because, on the one hand, lots of new data can be expected from the LHC experiments in the coming years, and, at the same time the hadronic uncertainties in these modes are under reasonable theoretical control thanks to the systematic expansion in inverse powers of the heavy b-quark mass. By taking into account improved theoretical predictions on hadronic parameters, such as transition form factors, and by constructing optimized observables with reduced sensitivity on hadronic uncertainties, we are going to explore and classify various signatures of possible NP effects in angular distributions and decay asymmetries. In addition, we plan to investigate rare FCNC decays of c-quarks with similar theoretical methods.

由口味变化中性电流（FCNCs）引起的夸克衰变是探索粒子物理标准模型（SM）边界的重要工具。在SM中，这些衰减被Cabibbo-Kobayashi-Maskawa （CKM）矩阵中的小混合角和/或轻夸克的小汤川耦合（GIM机制）所抑制。在SM的扩展中，并不一定实现类似的有效抑制机制，因此“新物理”（NP）信号可以在衰减率和不对称性中表现出来。在理论方面，低能量的fcnc过程是用有效哈密顿量来描述的，它允许考虑SM及其可能的扩展的贡献，包括，例如，来自右手电流或cp违反的新来源的影响。到目前为止，我们已经观察到许多基于b-夸克向s-夸克转变的过程；第一个数据也可以用于b到d衰减模式，它们被更小的CKM角进一步抑制。涉及上型夸克（u, c, t）的FCNCs的情况不太先进，部分原因是对相应衰变速率的抑制仍然更强。在这个项目中，我们计划对含有b-夸克的强子的各种独占FCNC衰变进行全面的理论研究。这种衰变非常适合于测试SM内外的基本相互作用，因为一方面，在未来几年中，LHC实验可以获得大量新数据，同时，由于重b-夸克质量的逆幂的系统扩展，这些模式中的强子不确定性在合理的理论控制下。考虑到对强子参数（如跃迁形状因子）的改进理论预测，并通过构建对强子不确定性敏感度降低的优化观测值，我们将探索和分类角分布和衰变不对称中可能的NP效应的各种特征。此外，我们计划用类似的理论方法研究罕见的c-夸克FCNC衰变。