Various lepton-flavor violating (LFV) processes in the supersymmetric standard model with right-handed neutrino supermultiplets are investigated in detail. It is shown that large LFV rates are obtained when tan β is large. In the case where the mixing matrix in the lepton sector has a similar structure as the KobayashiMaskawa matrix and the third-generation Yukawa coupling is as large as that of the top quark, the branching ratios can be as large as Br(µ → eγ) ≃ 10 −11 and Br(τ → µγ) ≃ 10 −7 , which are within the reach of future experiments. If we assume a large mixing angle solution to the atmospheric neutrino problem, rate for the process τ → µγ becomes larger. We also discuss the difference between our case and the case of the minimal SU (5) grand unified theory.

We examine the lepton-flavor violation caused by a Yukawa coupling matrix y ν,ij for right-handed neutrinos in the supersymmetric standard model. We stress that decay rates for τ → µγ and µ → eγ may reach the range to be accessible to near future experiments if left-right mixing terms in the slepton mass matrix are substantially large.

We systematically construct gauge-mediated supersymmetry-͑SUSY-͒breaking models with direct transmission of SUSY-breaking effects to the standard-model sector. We obtain a natural model with the gravitino mass m 3/2 smaller than 1 keV as required from the standard cosmology. If all Yukawa coupling constants are of order one, the SUSY-breaking scale m SUSY transmitted into the standard-model sector is given by m SUSY Ӎ0.1(␣ i /4)⌳ where ⌳ is the original dynamical SUSY-breaking scale. Imposing m SUSY Ӎ(10 2 -10 3 ) GeV, we get ⌳Ӎ(10 5 -10 6 ) GeV, which yields the gravitino mass m 3/2 Ӎ(10 Ϫ2 -1͒ keV.

The conclusions of the Physics Working Group of the International Scoping Study of a future Neutrino Factory and super-beam facility (the ISS) are presented. The ISS was carried out by the international community between NuFact05, (the 7th International Workshop on Neutrino Factories and Super-beams, Laboratori Nazionali di Frascati, Rome, 21-26 June 2005) and NuFact06 (Ivine, CA, 24-30 August 2006). The physics case for an extensive experimental programme to understand the properties of the neutrino is presented and the role of high-precision measurements of neutrino oscillations within this programme is discussed in detail. The performance of second-generation super-beam experiments, beta-beam facilities and the Neutrino Factory are evaluated and a quantitative comparison of the discovery potential of the three classes of facility is presented. High-precision studies of the properties of the muon are complementary to the study of neutrino oscillations. The Neutrino Factory has the potential to provide extremely intense muon beams and the physics potential of such beams is discussed in the final section of the report.