München 2009 – scientific programme

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T: Fachverband Teilchenphysik

T 16: Flavorphysik (Theorie) 3

T 16.8: Talk

Thursday, March 12, 2009, 18:30–18:45, M001

The Cabibbo angle in D₁4 — •Alexander Blum¹ and Claudia Hagedorn² — ¹Max-Planck-Institut für Kernphysik, Heidelberg — ²Scuola Internazionale Superiore di Studi Avanzati, Trieste, Italien

A supersymmetric model with the flavor symmetry D₁₄ is presented, which predicts the value of the CKM matrix element |V_ud| and thus the Cabibbo angle θ_C to be |V_ud| =cos( π/14 ) ≈ 0.97493 and sin( θ_C ) ≈ |V_us| = sin( π/14 ) ≈ 0.2225. D₁₄ is spontaneously broken by flavons, which are scalar gauge singlets. The prediction of |V_ud| (θ_C) is based on the fact that different Z₂ subgroups of D₁₄ are conserved in the up and the down quark sector. In order to achieve this D₁₄ is accompanied by a Z₃ symmetry. The quark mass hierarchy is partly due to the flavor symmetry D₁₄ and partly due to a Froggatt-Nielsen symmetry U(1)_FN under which only the right-handed quarks transform. The model is completely natural in the sense that all hierarchies observed among the quark masses and mixing angles are generated with the help of symmetries. The crucial issue of the vacuum alignment of the flavons is solved (up to a small number of degeneracies). A study of the next-to-leading order corrections shows that results achieved at the lowest order are only slightly perturbed. This fact also allows |V_ud| (θ_C) to be well inside the small experimental error bars.