König Matthias, Neubert Matthias, Straub David M
PRISMA Cluster of Excellence and Mainz Institute for Theoretical Physics, Johannes Gutenberg University, 55099 Mainz, Germany.
PRISMA Cluster of Excellence and Mainz Institute for Theoretical Physics, Johannes Gutenberg University, 55099 Mainz, Germany ; Department of Physics, LEPP, Cornell University, Ithaca, NY 14853 USA.
Eur Phys J C Part Fields. 2014;74(7):2945. doi: 10.1140/epjc/s10052-014-2945-9. Epub 2014 Jul 23.
Flavour- and CP-violating electromagnetic or chromomagnetic dipole operators in the quark sector are generated in a large class of new physics models and are strongly constrained by measurements of the neutron electric dipole moment and observables sensitive to flavour-changing neutral currents, such as the [Formula: see text] branching ratio and [Formula: see text]. After a model-independent discussion of the relevant constraints, we analyze these effects in models with partial compositeness, where the quarks get their masses by mixing with vector-like composite fermions. These scenarios can be seen as the low-energy limit of composite Higgs or warped extra dimensional models. We study different choices for the electroweak representations of the composite fermions motivated by electroweak precision tests as well as different flavour structures, including flavour anarchy and [Formula: see text] or [Formula: see text] flavour symmetries in the strong sector. In models with "wrong-chirality" Yukawa couplings, we find a strong bound from the neutron electric dipole moment, irrespective of the flavour structure. In the case of flavour anarchy, we also find strong bounds from flavour-violating dipoles, while these constraints are mild in the flavour-symmetric models.
夸克领域中违反味和电荷宇称的电磁或色磁偶极算符在一大类新物理模型中产生，并受到中子电偶极矩测量以及对味改变中性流敏感的可观测量（如[公式：见正文]分支比和[公式：见正文]）的严格限制。在对相关限制进行与模型无关的讨论之后，我们在部分复合模型中分析这些效应，在这类模型中夸克通过与矢量类复合费米子混合获得质量。这些情景可被视为复合希格斯或弯曲额外维度模型的低能极限。我们研究了由电弱精确测试推动的复合费米子电弱表示的不同选择以及不同的味结构，包括味无规性以及强相互作用领域中的[公式：见正文]或[公式：见正文]味对称性。在具有“错误手征性”汤川耦合的模型中，无论味结构如何，我们都从中子电偶极矩得到一个强限制。在味无规性的情况下，我们还从违反味的偶极得到强限制，而在味对称模型中这些限制较为宽松。
