Supersymmetric SO(10) Seesaw Mechanism with Low $B\mathrm{\text{−}}L$ Scale

We propose a new seesaw mechanism for neutrino masses within a class of supersymmetric SO(10) models with broken $D$ parity. It is shown that in such scenarios the $B\mathrm{\text{−}}L$ scale can be as low as TeV without generating inconsistencies with gauge coupling unification nor with the required magnitude of the light neutrino masses. This leads to a possibly light new neutral gauge boson as well as relatively light quasi-Dirac heavy leptons. These particles could be at the TeV scale and mediate lepton flavor and $CP$ violating processes at appreciable levels.

Figure 1

The proposed supersymmetric SO(10) seesaw mechanism comes from this graph, up to transposition. The neutrino mass is suppressed by the unification scale, not by the $B\mathrm{\text{−}}L$ breaking scale, which can be low.

Figure 2

The one-loop gauge coupling unification in the model described in the text. The $D$ parity is broken at $M_G$, and the intermediate scales $V_R$ and $v_R$ correspond to $\mathrm{SU}(2{)}_R\to \mathrm{U}(1{)}_R$ and $\mathrm{U}(1{)}_R\otimes \mathrm{U}(1{)}_{B-L}\to \mathrm{U}(1{)}_Y$ breaking, respectively.

Figure 3

Same as in Fig. 2 for the case of higher $v_R$. As expected, the prediction for ${\alpha }_1^{-1}(M_Z)$ does not depend on the position of the $v_R$ scale.