μ → eγ decay versus the μ → eee bound and lepton flavor violating processes in supernova

Even tiny lepton flavor violation (LFV) due to some New Physics is able to alter the conditions inside a collapsing supernova core and probably to facilitate the explosion. LFV emerges naturally in a see-saw type-II model of neutrino mass generation. Experimentally, the LFV beyond the Standard Model is constrained by rare lepton decay searches. In particular, strong bounds are imposed on the mu -> eee branching ratio and on the mu-e conversion in muonic gold. Currently, the mu -> e gamma is under investigation in the MEG experiment that aims at a dramatic increase in sensitivity in the next three years. We seek a see-saw type-II LFV pattern that fits all the experimental constraints, leads to Br(mu -> e gamma) a parts per thousand(3) Br(mu mu -> eee), and ensures a rate of LFV processes in supernova high enough to modify the supernova physics. These requirements are sufficient to eliminate almost all freedom in the model. In particular, they lead to the prediction 0.4 x 10(-12) a parts per thousand(2) Br(mu -> e gamma) a parts per thousand(2) 6 x 10(-12), which will be testable by MEG in the nearest future. The considered scenario also constrains the neutrino mass-mixing pattern and provides lower and upper bounds on tau-lepton LFV decays. We also briefly discuss a model with a single bilepton in which the mu -> eee decay is absent at the tree level.