1. Aug. 16, 2003Mitsuru Kakizaki1 Democratic (s)fermions and lepton flavor violation Mitsuru Kakizaki （ Tohoku Univ. ） Aug. 16, 2003 Ref.: K. Hamaguchi, M. K. and Masahiro Yamaguchi, to appear in PRD, hep-ph/0212172 Proposal of a new alignment mechanism based on the democratic mass matrices Comparison between alignment and the conventional mSUGRA

2. Aug. 16, 2003Mitsuru Kakizaki2 １． Motivation Two severe flavor problems in SUSY models The flavor problem of fermion masses The charged fermion mass hierarchy Small quark mixing but bi-large lepton mixing The flavor problem of sfermion masses Generic flavor mixing among sfermions Large FCNC In order to be consistent with experiments

3. Aug. 16, 2003Mitsuru Kakizaki3 Attempts to solve SUSY flavor problem Degeneracy: Decoupling: Alignment: Idea: A high energy theory which controls flavor FCNC suppression Fermion masses and mixings Measurement of FC processes and sfermion mass spectra We can find the fermion mass generation mechanism

4. Aug. 16, 2003Mitsuru Kakizaki4 Purposes of this talk Proposal of a new alignment mechanism based on the democratic mass matrices Comparison between alignment and the conventional mSUGRA Sfermion masses Flavor changing processes

5. Aug. 16, 2003Mitsuru Kakizaki5 2. Democratic mass matrix Idea: equality of three generations The permutation group on 3 objects: : a 3 reducible representation The third generation: 3 = 1 + 2 The light generations:

6. Aug. 16, 2003Mitsuru Kakizaki6 The charged lepton mass matrix sym. The democratic matrix: The unique invariant Small breaking The mass hierarchy: Bi-large unitary matrices:

7. Aug. 16, 2003Mitsuru Kakizaki7 The neutrino mass matrix We consider majorana neutrinos: sym. Universal Democratic We assume absence of the democratic part: Degenerate neutrinos Bi-large mixing and small U e3

8. Aug. 16, 2003Mitsuru Kakizaki8 3. Democratic sfermions Idea: Interactions between the MSSM fields and hidden fields also obey the democracy Soft scalar mass matrices: In the fermion mass basis, Non-universal masses but small flavor mixing Alignment

9. Aug. 16, 2003Mitsuru Kakizaki9 Slepton masses Left-handed slepton masses Bi-large neutrino mixing requires absence of the democratic part of the Kahler potential for No LFV Right-handed slepton masses Small flavor mixing LFV

10. Aug. 16, 2003Mitsuru Kakizaki10 The present experimental bound (MEGA (1999)): Future sensitivity (PSI) :

11. Aug. 16, 2003Mitsuru Kakizaki11 Degeneracy vs alignment MSSM + (mSUGRA + RG effects) Collider experiments: LFV searches: Democratic ansatz Searches with polarized muons are promising

12. Aug. 16, 2003Mitsuru Kakizaki12 4. Summary An interesting solution for the SUSY flavor problem The mechanism which controls fermion mass structure also dictates FCNC suppression Predictions in the democratic approach Observable We can distinguish models of flavor by collider experiments and LFV searches

13. Aug. 16, 2003Mitsuru Kakizaki13 Problems What is the origin of the democratic matrices? Symmetry Geometry What is the origin of the small S 3 breaking parameters? Why is the democratic part absent for ?