DT2: Flavour physics in supersymmetric theories

Supersymmetric extensions of the standard model belong to the best motivated candidate of theories of new physics. Many of these models, like the minimal supersymmetric standard model, have a large number of additional free parameters such that it is usually difficult to make definitive predictions. An exception to this rule are supersymmetric unified theories (SUSY GUTs). Due to the high symmetry at the GUT scale these models are fixed by a number of parameters which is less than for the standard model. Nevertheless these models can completely describe quark and lepton masses and the CKM quark and PMNS neutrino mixing matrices. Once the model parameter are determined predictions can be made for example for flavour changing neutral currents (FCNC). In [1] it was shown for a SO(10) SUSY GUT model [2] that a simultaneous description of quark and lepton masses and mixings as well as FCNCs like B_s→μ⁺μ^-, B→X_sγ and B→X_sl⁺l^-, is only possible if the supersymmetric partners of quarks and leptons are unnaturally heavy. Starting from this the question should be answered whether this is a property of the specific model which has been scrutinized or whether similar statements can be made for a broad class of SUSY GUTs. It is particularly interesting to clarify the role of the unification of t, b, and τ Yukawa couplings which often appear in SUSY GUTs and how SUSY GUTs must be modified to descript FCNCs adequately.

References:

1. M. Albrecht, W. Altmannshofer, A.J. Buras, D. Guadagnoli and D. M. Straub,
   Challenging SO(10) SUSY GUTs with family symmetries through FCNC processes,
   JHEP 0710 (2007) 055, 0707.3954 [hep-ph]
2. R. Dermisek and S. Raby,
   Bi-large neutrino mixing and CP violation in an SO(10) SUSY GUT for fermion masses,
   Phys. Lett. B622 (2005) 327, hep-ph/0507045.