Abstract :
In the minimal supersymmetric standard model, we have studied the evolution of the neutrino flavor mixing by using the renormalization group equation (RGE) with the Georgi-Jarlskog texture for the Yukawa coupling matrices. For the large Yukawa coupling of the charged lepton, i.e., tan β ⪢ 1, the neutrino flavor mixing increases significantly with running down to the electroweak scale by the RGE. If one wishes to get the large neutrino flavor mixing sin θ23 at the electroweak scale, which is suggested by the muon neutrino deficit in the atmospheric neutrino flux, the initial condition sin θ23 ≥ 0.27 is required at the GUT scale. Combined with the see-saw enhancement of the neutrino flavor mixing, the large mixing is naturally reproduced by setting the reasonable initial condition.
