Neutrino masses and lepton flavor violation in thick brane scenarios - art. no. 073005

We address the issue of lepton flavor violation and neutrino masses in the "fat-brane" paradigm, where flavor changing processes are suppressed by loc alizing different fermion field wave functions at different positions (in t he extra dimensions) in a thick brane. We study the consequences of suppres sing lepton number violating charged lepton decays within this scenario for lepton masses and mixing angles. In particular, we find that charged lepto n mass matrices are constrained to be quasidiagonal. We further consider wh ether the same paradigm can be used to naturally explain small Dirac neutri no masses by considering the existence of three right-handed neutrinos in t he brane, and discuss the requirements to obtain phenomenologically viable neutrino masses and mixing angles. Finally, we examine models where neutrin os obtain a small Majorana mass by breaking lepton number in a far away bra ne and show that, if the fat-brane paradigm is the solution to the absence of lepton number violating charged lepton decays, such models predict, in t he absence of flavor symmetries, that charged lepton flavor violation will be observed in the next round of rare muon or tau decay experiments.