The interplay between neutrinos and charged leptons in the minimal SU(3)L×U(1)N gauge model Original Research Article

In the minimal SU(3)L×U(1)N gauge model with a global Le–Lμ–Lτ (=L′) symmetry and a discrete Z4 symmetry, it is found that the interplay between neutrinos and charged leptons contained in triplets of ψi=νiL,ℓiL,ℓciL (i=1,2,3) naturally leads to the large mixing angle (LMA) MSW solution. The model includes two (anti)sextet Higgs scalars, S(0) with L′=0 and S(+) with L′=2, which, respectively, couple to ψ1ψ2,3 for the electron mass and masses of atmospheric neutrinos and to ψ2,3ψ2,3 for the μ- and τ-masses and one-loop radiative neutrino masses relevant to solar neutrinos. This mechanism is realized by utilizing an additional residual discrete symmetry supplied by explicitly broken L′, which guarantees the absence of tree-level neutrino mass terms of the ψ2,3ψ2,3-type. Pure rotation effects due to the diagonalization of neutrino and charged-lepton mass matrices are estimated to yield Δm2⊙/Δm2atm≲(me/mμ)3/2=O(10−4) but the radiative effects supersede the rotation effects to yield Δm2⊙/Δm2atm=O(10−2) as the LMA solution.