Flavor and CP in supersymmetric extensions of the Standard Model

• Applicant: Professor Dr. Andreas Weiler, since 8/2018
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: from 2014 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 249999962

The main objective of this project is to address the question of the origin of flavor and CP violation in supersymmetric extensions of the Standard Model. Gaining new insights into these issues requires, in particular, a better understanding of the Kähler potential for several reasons. The Kähler potential mainly determines the soft mass pattern, which is eminent for the low-energy phenomenology of such theories. In particular, mixing among the scalar fields can induce flavor changing and CP violating processes among the matter particles. Moreover, the Kähler potential is not protected by the supersymmetric non-renormalization theorems and is corrected at the quantum level. This changes the field normalizations and determines the evolution of the couplings. In addition, the Kähler potential is less constrained by ordinary symmetries than the superpotential. Indeed, in a bottom-up approach it is difficult to control the size and existence of higher-order terms. This leads to non-negligible corrections to models with flavor symmetries. We will use three complementary strategies to solve these issues. In the first approach, we will analyze the problem bottom-up in supersymmetric gauge theories using, e.g., R symmetries, anomaly considerations and renormalization group invariants. Furthermore, we will compute the Kähler potential in higher-dimensional Grand Unified Theories. In these more constrained models, one has better control on the couplings in the Kähler potential because one can relate them to geometric properties like wave function overlaps. The third approach is to directly work out the Kähler potential in certain possibly realistic string compactifications like orbifolds. All these approaches should lead to mutually consistent results. Within all three approaches we will then try to obtain new information on the flavor structure and the breaking of the CP symmetry. A well-known bottom-up technique is to impose non-Abelian discrete flavor symmetries. However, most of the corresponding models do not make any predictions concerning CP violation. We will preclude scenarios where CP violation cannot be explained at all or only with unnatural fine tuning. This will not only be physically relevant but also be based on so far unexplored mathematical techniques related to the outer automorphism group of flavor symmetries, which is known to be related to the CP symmetry. A study of higher-dimensional Grand Unified Theories and string theories, in which the origin of discrete flavor symmetries is well understood since they originate from additional compact extra dimensions, will enable us to identify phenomenologically viable scenarios.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Professor Dr. Michael Ratz, until 8/2018