Lepton Flavor Violating Process in Degenerate and Inverse-Hierarchical Neutrino Models

We have investigated the lepton flavor violation in the supersymmetric framework assuming the large mixing angle MSW solution with the quasi-degenerate and the inverse-hierarchical neutrino masses. In the case of the quasi-degenerate neutrinos, the predicted branching ratio BR(μ → eγ) strongly depends onmν and Ue3. For Ue3 ≃ 0.05 with mν ≃ 0.3 eV, the prediction is close to the present experimental upper bound. On the other hand, the prediction is larger than the experimental upper bound for Ue3 ≥ 0.05 in the case of the inverse-hierarchical neutrino masses. E-mail address: [email protected] E-mail address: [email protected] E-mail address: [email protected] E-mail address: [email protected] Super-Kamiokande has almost confirmed the neutrino oscillation in the atmospheric neutrinos, which favors the νμ → ντ process [1]. For the solar neutrinos [2, 3], the recent data of the Super-Kamiokande and SNO also favor the neutrino oscillation νμ → νe with the large mixing angle(LMA) MSW solution [4, 5]. These results mean that neutrinos are massive, moreover, they indicate the bi-large flavor mixing in the lepton sector. The non-zero neutrino masses clearly imply new physics beyond the standard model(SM), and the large flavor mixings suggest that the flavor structure in the lepton sector is very different from that in the quark sector. If neutrinos are massive and mixed in the SM, there exists a source of the lepton flavor violation (LFV). However, due to the smallness of the neutrino masses, the predicted branching ratios for these processes are tiny such as BR(μ → eγ) < 10. On the other hand, in the supersymmetric framework the situation is completely different. The SUSY provides new direct sources of flavor violation in the lepton sector, namely the possible presence of off-diagonal soft terms in the slepton mass matrices ( m L̃ )