Leptogenesis with cosmic strings

Abstract

A new scenario for baryogenesis is described. The basic idea is that theories beyond the standard model which contain a $\mathrm{U}(1{)}_{B-L}$ gauge symmetry, where $B$ and $L$ are respectively baryon and lepton numbers, predict the existence of $B-L$ cosmic strings with right-handed neutrinos trapped as transverse zero modes. Cosmic string loops loose their energy via gravitational radiation and rapidly decay releasing these right-handed neutrinos. These decay into lepton and electroweak Higgs boson producing an initial lepton asymmetry. This lepton asymmetry is then converted into a baryon asymmetry via sphaleron transitions. The minimal extension of the standard model and the minimal grand unified theory for which this scenario works are respectively $\mathrm{SU}(3{)}_c\times \mathrm{SU}(2{)}_L\times \mathrm{U}(1{)}_R\times \mathrm{U}(1{)}_{B-L}$ and SO(10).

Published in the Proceedings of the XXXIInd Rencontres de Moriond on ``Electroweak Interactions and Unified Theories'', Les Arcs, Savoie, France, March 15-22, 1997