text: The nonvanishing neutrino masses have been conﬁrmed by various neutrino oscillation 
  
  phenomena and indicate the evidence of new physics beyond the Standard Model. The most 
  
  attractive idea to naturally explain the tiny neutrino masses is the seesaw mechanism [1], in 
  
  which the right-handed (RH) neutrinos singlet under the SM gauge group are introduced. 
  U(1)Y × 
  L model based on the gauge group SU(3)C × 
  L [2] is an elegant and simple extension of the SM, in which the RH neutrinos of 
  
  The minimal gauged U(1)B 
  SU(2)L × 
  − 
  
  U(1)B 
  − 
  
  three generations are necessarily introduced because of the gauge and gravitational anomaly 
  
  In addition, the mass of RH neutrinos arises associated with the U(1)B  cancellations.  L 
  − 
  
  gauge symmetry breaking. 
  
  Although the scale of the B  L gauge symmetry breaking is basically arbitrary as long as 
  − 
  
  phenomenological constraints are satisﬁed, one interesting option is to take it to be the TeV 
  
  scale [3]. It has been recently pointed out [4] that when the classical conformal invariance 