Higgs boson couplings to quarks with supersymmetric CP and flavor violations

In minimal supersymmetric model (SUSY) with a light Higgs sector, explicit CP violation and most general flavor mixings in the sfermion sector, integration of the superpartners out of the spectrum induces potentially large contributions to the Yukawa couplings of light quarks via those of the heavier ones. These corrections can be sizeable even for moderate values of tan β, and remain nonvanishing even if all superpartners decouple. When the SUSY breaking scale is close to the electroweak scale, the Higgs exchange effects can compete with the gauge boson and box diagram contributions to rare processes, and their partial cancellations can lead to relaxation of the existing bounds on flavor violation sources. In this case there exist sizeable enhancements in flavor–changing Higgs decays. When the superpartners completely decouple, however, the Higgs mediation becomes the dominant SUSY contribution to rare processes the saturation of which, without a strong suppression of the flavor mixings, prefers large tan β and certain ranges for the CP–odd phases. The decay rate of the lightest Higgs into light down quarks become comparable with that into the bottom quark. Moreover, the Higgs decay into the up quark is significantly enhanced. There are observable implications for rare processes, atomic electric dipole moments, and collider searches for Higgs bosons. The standard model of electroweak interactions (SM) has been extremely successful in explaning all the available data. The least understood aspects of the model concern the breaking of gauge, CP and flavor symmetries. Indeed, the Higgs boson mass and various parameters in the Yukawa matrices are left to experimental determination. Though the indications at LEP for a light Higgs boson of mass ∼ 115 GeV are encouraging a full construction of the symmetry–breaking sector, icluding possibly its CP properties, is to wait for the upgraded Tevatron or LHC. On the other hand, existing as well as future data to come from the experiments on kaon, beauty and charmed hadrons will determine the structure of CP and flavor violations. The scalar sector, which is responsible for breaking the gauge symmetry, is quadratically sensitive to the UV cut–off and hence the model must be embedded into a UV–safe extension beyond the TeV scale. Supersymmetry (SUSY) is the only weak–scale extension which stabilizes the Higgs sector against quadratic divergences and unifies the gauge couplings at high energies in agreement with the electroweak precision data. Quite generically, the SUSY models bring about novel sources for CP and flavor violations through the soft breaking masses. The main reason for SUSY flavor violation is that the fermions and sfermions are misaligned in the flavor space, and even if the flavor violation in the fermion sector is reduced to that of the CKM matrix the sfermion sector maintains its non–CKM structure. The LR and RL=LR blocks of the sfermion mass–squared matrices are generated after the electroweak breaking with the maximal size O(mtMSUSY ). The nontrivial flavor structures of these blocks are dictated by the Yukawa couplings Yu,d and by the trilinear coupling matrices Y u,d with ( Y u ) ij = (Yu)ij (Au)ij and ( Y d ) ij = (Yd)ij (Ad)ij (1) where Au,d are not necessarily unitary so that even their diagonal entries contribute to CP– violating observables. The LL and RR blocks are insensitive to electroweak breaking, and their texture is determined by the SUSY breaking pattern. In minimal SUGRA and its nonuniversal variants with CP violation, for instance, size and structure of flavor and CP violation in LL and RR blocks are dictated by the CKM matrix [1]. On the other hand, in SUSY GUTs with Yukawa unification e.g. SO(10), implementation of the see–saw mechanism for neutrino masses implies sizeable flavor violation in the RR block, given the large mixings observed in atmospheric neutrino data [2]. Independent of specific realizations, the squark mass–squared matrices can be paramterized as