Chargino Exchange Research Articles

On soft breaking and CP phases in the supersymmetric standard model

We consider a class of N = 1 supersymmetric extensions of the Standard Model in which the soft breaking sector is CP conserving at the GUT scale. We study the question of whether the presence of explicit CP violation in the Yukawa sector of the theory induces through renormalization effects CP violating phases in the soft terms, which could lead to observable effects. A clear pattern appears in the structure of phases in the soft sector. In particular, the inclusion of intergenerational mixing induces large phases in the flavour mixing entries of the trilinear soft breaking terms, whereas the diagonal entries remain real. A mechanism is proposed for generating through chargino exchange a contribution to the neutron electric dipole moment which can be a few orders of magnitude larger than that of the Standard Model, although still out of reach of experimental tests. We comment on the possible relevance of these phases for baryogenesis at the weak scale in minimal supersymmetric scenarios, recently considered in the literature.

Supersymmetric contributions to b → s + H

We analyze the conditions for the presence of light neutral Higgs scalars in a class of low-energy N = 1 supergravity models where the SU(2) L × U(1) gauge-symmetry breaking is induced by renormalization effects. We study the implications on the mass of such light scalars arising from their possible emission in the flavor-changing transition b → s + H. Gluino and chargino exchange contributions are considered and shown to be sizeably large. It is argued that a lower bound of about 4 GeV on the scalar mass may be inferred from the present experimental data, barring contrived choices of the relevant supersymmetric parameters.