Flavour Problem and Family Symmetry beyond the Standard Model

Dear Colleagues,

The Standard Model (SM), in the currently available energy range, agrees very well with the experimental results. However, generally, it is not considered as a complete theory, because it does not provide answers to many pressing questions.  Many of these unresolved problems combine with the so-called flavour problem. The SM does not completely explain why its quarks and leptons sectors are so different; it does not explain the nature of neutrinos (Dirac or Majorana), their masses and parameters of the mixing matrix. All these parameters are determined experimentally and not theoretically predicted. In general, there are three approaches to this matter. The first one derives from a theory that assumes a substructure for the fundamental fermions — the preons theory; the second is based on the grand unification theories; and the third, the family symmetries, which are sometimes also called the horizontal or flavour symmetries.

In the flavour symmetry approach, such additional symmetry between quark and lepton gauge doublets and Higgs doublets, triplets or singlets (depends on the SM extensions) should be sought for. These will give fermion mass matrices from which the determined masses, mixing angles, and the CP symmetry breaking phases are in agreement with experimental data.

Prof. Dr. Marek Zrałek
Dr. Bartosz Dziewit
Guest Editors

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• family symmetries
• SM parameters
• quark and lepton masses
• CKM and PMNS mixing matrix
• group theory applications
• CP violation
• Dirac and Majorana neutrinos
• discrete symmetries