Jean-Marie Frère

Fermion masses and induction of the weak scale by supergravity

Abstract We discuss some problems which arise in a low-energy theory of strong and electroweak interactions when the weak scale is induced via supergravity. The main problem concerns the origin of quark and lepton masses. If the fermions obtain their masses in the conventional way via Yukawa couplings, then the low-energy supergap (mass difference between supersymmetric partners) is comparable to the mass of the lightest massive fermion. One solution would require that at least the light generations receive their mass indirectly via radiative corrections. Alternatively it might be that the SU(2) × U(1) breaking is induced radiatively.

On the Possibility of Finding Light Uncolored Supersymmetric Partners at Present and Future Machines

Supersymmetric models allow the possibility of finding new light spin-12 fermions (m <mw, and perhaps m < 10–15 GeV, charged or neutral) that are (apart from mixing effects) the supersymmetric partners of W, Z0, and Higgs bosons. We provide a detailed analysis of their expected properties, production mechanisms, and signatures, with emphasis on detection at e+e- colliders. Although the charged, spin-12 particles resemble sequential leptons, it turns out that their properties differ enough that they might have been missed in the standard searches with normal cuts, and they still might be found with m < 18 GeV. A neutral, spin-12 particle with m below about 30 GeV could exist with a clear decay signature and be singly produced at detectable rates at present machines (picobarn cross sections).

Supersymmetric contributions to the ϵ′ and ϵ CP violating parameters

Abstract We consider the contributions to ϵ, ϵ′ ϵ and the electric dipole moments due to flavor blind mechanisms of CP violation, found in supersymmetric models.

CP VIOLATION IN THE LEPTON SECTOR WITH SMALL NEUTRINO MASSES

Small, even vanishing neutrino masses are consistent with large CP violation effects in the leptonic sector. As an example, and a proof of existence of this situation, we present a model based on the SU(2)L × SU(2)R × U(1) gauge symmetry, where the fermion content has been Extended to include a gauge singlet lepton SL. Interesting features of this model (which should be seen as a mere example) are: (1) neutrino masses can either vanish or be in the range where the Mikheyev-Smirnov-Wolfenstein (MSW) mechanism for the solar neutrino puzzle is operative, and (2) CP violation effects in the lepton sector are manifestly large and therefore accessible to current experiments. In particular, it is found that the electron electric dipole moment, drme, can be of order 10−24e·cm; if generation mixing is negligible, the μ longitudinal polarization, PrmL, in the decay KL → μμ can be in the range 10−10−10−3.

Strong radiative corrections to strangeness-changing processes in the presence of right-handed currents

Abstract In the presence of weak right-handed currents the GIM suppression becomes less efficient in the effective ΔS =2 operator. Therefore new features arise and have to be taken into account when applying strong radiative corrections. We determine these QCD corrections to the ΔS =2 operator on the leading log level and (in contrast to the standard model) find a sizeable enhancement. If one ascribes CP violation to the presence of right-handed currents, then the parameter ϵ will enjoy the same enhancement. We show however that ϵ ′ is increased in a similar way; the ratio ϵ′ ϵ is therefore not significantly affected.