Neutrino Mass and the SU(2)_R Breaking Scale

The neutrino sector in a left-right extension of the Standard Model depends on how SU(2)_R is broken. I list all possible scenarios, including the ones where the Majorana nu_R mass is naturally much smaller than the SU(2)_R breaking scale, which is desirable for generating the proper baryon asymmetry of the Universe. The best such choice is identified and discussed.