We examine extensions of the MSSM with more than one generation of Higgs bosons. If one assumes that a symmetry eliminates the tree-level FCNC, then the extra scalar bosons do not acquire VEVs, do not couple to fermions and do not mix with the ordinary Higgs bosons; the lightest is absolutely stable. The two lightest neutral scalars, φS , and φP , are degenerate in mass, and the mass difference...

We present results of our study of tanβ -enhanced loop corrections in the Minimal Supersymmetric Standard Model (MSSM) with Minimal Flavour Violation (MFV). We demonstrate that these corrections induce flavour changing neutral current (FCNC) gluino couplings which have a large impact on the Wilson coefficient C8 of the chromomagnetic operator. To illustrate the phenomenological consequences of ...

We revise the limits on the FCNC higgses in manifestly left-right symmetric theories. It is shown that the combination of the Kobayashi-Maskawa CP-violation with the tree level ∆S = 2 higgs exchange gives very large contribution to the CPviolating ǫ parameter. It leads to the new strong constraint on the FCNC higgs mass, M > 50 − 100 TeV, enhanced almost by factor of the order √ mt/mc. Being ad...

The solution to the supersymmetric FCNC problem may not have a simple field theory interpretation. Here I advocate a possibility based on string selection rules. The requirement of non–trivial Yukawa structures restricts the form of the soft terms such that the FCNC problem often does not arise.

Flavor Changing Neutral Current decays of the top quark within the strict context of the Standard Model are known to be extremely rare. In fact, they are hopelessly undetectable at the Tevatron, LHC and LC in any of their scheduled upgradings. Therefore, if a few of these events eventually show up in the future we will have certainly discovered new physics. We argue that this could well be the ...

The tree level diagonalization of a neutrino mass matrix with both Majorana and Dirac masses is discussed in a general context. Flavor changing neutral currents in such models are inevitable. Rephasing invariant quantities characterizing CP violation in FCNC FermionHiggs interactions are identified. At the one loop level, the mass eigenstates become of an impure Majorana type. The Possibility o...

We examine the decays t → cγ and cZ 0 in the Standard Model with an extra scalar doublet and no discrete symmetry preventing tree-level flavour changing neutral currents. The Yukawa couplings of the new scalars are assumed to be proportional to fermion masses, evading bounds on FCNC's from the light quark sector. These rare top decays may be visible at the SSC.

Last few years, many people have studied the possibilities that the anomalous U(1) gauge symmetry is a trigger of SUSY breaking and/or an origin of the fermion mass hierarchy. Though it is interesting that the anomalous U(1) symmetry may explain the above two phenomena simultaneously, it causes a negative stop mass squared or a severe fine-tuning in order to avoid the FCNC problem. Recently it ...

CKM mixing between third family quarks and a possible fourth family is constrained by global fits to the precision electroweak data. The dominant constraint is from nondecoupling oblique corrections rather than the vertex correction to Z → bb used in previous analyses. The possibility of large mixing suggested by some recent analyses of FCNC processes is excluded, but 3-4 mixing of the same ord...

The aspon model provides an alternative to the KM mechanism for CP violation with the advantage that the strong CP problem is solved. We consider the incorporation of low-energy supersymmetry and find the constraints on alignment and squark degeneracy. The conclusion is that although the θ̄ constraints are much less severe than in other generic schemes with supersymmetry breaking and spontaneous...