Allowable Low-Energy E_6 Subgroups from Leptogenesis

Abstract

There are only two viable low-energy $E_6$ subgroups: $SU(3{)}_C\times SU(2{)}_L\times U(1{)}_Y\times U(1{)}_N$ or $SU(3{)}_C\times SU(2{)}_L\times SU(2{)}_R^{\prime }\times U(1{)}_{Y_L+Y_R^{\prime }}$, which would not erase any preexisting lepton asymmetry of the Universe that may have been created by the decay of heavy singlet (right-handed) neutrinos or any other mechanism. They are also the two most favored $E_6$ subgroups from a recent analysis of present neutral-current data. We study details of the leptogenesis, as well as some salient experimental signatures of the two models.

12 pages