A realistic theory of family unification

Jonathan A. Bagger, Savas Dimopoulos, Eduard Massó, M.Hall Reno
1985 Nuclear Physics B  
We develop an 0(18) theory of family unification consistent with all established phenomenology and cosmology. The theory makes firm predictions that will be tested soon. It implies that five new families live below 265 GeV. One of the new families is left-handed, and the other four are right-handed. The new left-handed family is lighter than its right-handed counterparts. The lightest right-handed quark should have a mass of less than 130 GeV. All the charged . a-leptons should be lighter than
more » ... ld be lighter than 55 GeV; the lightest should be less than 40 GeV. The five new neutrinos have Dirac masses of less than 40 GeV, so a total of eight doublet neutrinos contribute to the width of the 2'. We study the decays of new families, and show that proton decay into et-r" proceeds at an observable but acceptable rate, with a lifetime on the order of 1032*1 years. 2 * Another way to raise the mass of some of the neutrinos is to introduce an isotriplet of Higgs scalars. This possibility is ruled out by proton decay experiments. 9 * All right-handed neutrinos mix in the 26 models. In the 210 case, the story is more complicated. See Section 6. 33 The 0(18) models with one Higgs doublet give eight ultralight neutrinos, all with masses 2 .l eV. Such a large number of ultralight neutrinos is in apparent conflict with the simplest version of big-bang nucleosynthesis. Models with one Higgs doublet also require the existence of light Higgs singlets. The charged fermion spectrum, however, is similar to that of the two-Higgs model. In the one-Higgs case, all eight neutrinos contribute to the invisible decays of the 2'. This provides an important distinction between the one-and two-Higgs models. Both the one-and two-Higgs versions of 0(18) f amily unification predict that eight neutrinos should contribute to the width of the 2'. Furthermore, it is quite likely that at least one right-handed charged lepton also contributes to its width. Given the striking signatures discussed here, 0(18) cannot help but be tested a-soon.
doi:10.1016/0550-3213(85)90627-3 fatcat:gkcbme6hdnfd5kffvz53dq4vkm