Neutrino mass matrix with no adjustable parameters

On the basis of the so-called “yukawaon” model, we found a special form of the neutrino mass matrix M ν which gives reasonable predictions. The M ν is given by a multiplication form made of charged lepton mass matrix M e and up-quark mass matrix M u . This M ν has no adjustable parameters except for those in M e and M u . Here, M e and M u are described by one parameter a e (real) and two parameters a u (complex), respectively, and those parameters are constrained by their observed mass ratios. With this form of M ν , in spite of having only three parameters, the M ν can give reasonable predictions: sin 2 2 θ atm ≃0.99, sin 2 2 θ 13 ≃0.015, , 〈 m ee 〉≃0.0039 eV, and so on, by using observed values of m e / m μ , m μ / m τ , m c / m t , and sin 2 θ solar as input values.