Baryon and lepton number assignment in E6 models.

Abstract

In ${\mathrm{E}}_{6}$ models there are new particles whose baryon number is not uniquely assigned. We point out that the baryon and lepton number assignment to these particles can change the baryogenesis scenario significantly. We consider a left-right symmetric extension of the standard model in which the (B-L) quantum number is gauged. The identification of (B-L) with a generator of ${\mathrm{E}}_{6}$ is used to define the baryon and lepton numbers for the exotic particles in a way that the electroweak baryon and lepton number anomaly corresponding to the SU(2${)}_{\mathit{L}}$ group vanishes; i.e., there is no nonperturbative baryon or lepton number violation during the electroweak phase transition. We study some consequences of the new assignment.