We have derived the unitarity bounds in the high energy limit for the minimal
B-L extension of the Standard Model by analysing the full class of Higgs and
would-be Goldstone boson two-to-two scatterings at tree level. Moreover, we
have investigated how these limits could vary at some lower critical value of
the energy.Comment: 20 pages, 4 figures, 2 tables; 1d figure modified, typos corrected,
bibliography augmented; published in PRD after minor adjustmen