2014/07/31 by Biswajit Adhikary, Mainak Chakraborty, Ambar Ghosal · 18 citations
Physics and Astronomy · #Asymmetry #CP violation #Dark Matter and Cosmic Phenomena #Leptogenesis #Lepton #Neutrino #Neutrino Physics Research #Neutrino oscillation #Nuclear physics #Particle physics #Particle physics theoretical and experimental studies #Physics #Seesaw mechanism #Symmetry breaking #Yukawa potential #hep-ph
paper · pdf · doi:10.1103/physrevd.93.113001
published in Physical review. D/Physical review. D. 93(11) (American Physical Society) · 36 pages, 9 figures, 16 tables (Accepted for publication in Physical Review D)
arxiv created 2016/05/24 · openalex publication_date 2016/06/03 · arxiv updated 2016/06/08 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Cyclic symmetry in the neutrino sector with the type-I seesaw mechanism in the mass basis of charged leptons and right chiral neutrinos (NiR, i=e, \ensuremathμ, \ensuremathτ) generates a twofold degenerate light neutrino and a threefold degenerate heavy neutrino mass spectrum. Consequently, such a scheme produces vanishing one light neutrino mass squared difference and lepton asymmetry. To circumvent such an unphysical outcome, we break cyclic symmetry in the diagonal right chiral neutrino mass term by a small breaking parameter. Nonzero mass squared differences and mixing angles are generated with the help of the small breaking parameter. The smallness of the breaking parameter opens up the possibility of resonant leptogenesis. Assuming complex Yukawa couplings, we derive generalized expressions with flavor-dependent CP asymmetry parameters (ϵi^\ensuremathα) which are valid for the quasidegenerate as well as hierarchical mass spectrum of right-handed neutrinos. Thereafter, we set up the chain of coupled Boltzmann equations (which are flavor dependent too) which have to be solved in order to get the final lepton asymmetries. Depending upon the temperature regime, the CP asymmetries and the Boltzmann equations may also be flavor independent. As our goal is to study the enhancement of CP asymmetry due to the quasidegeneracy of right-handed neutrinos, we select only the lowest allowed (by neutrino oscillation data) value of the breaking parameter (and other corresponding Lagrangian parameters) and estimate the baryon asymmetry parameter YB. The experimental constraint of YB introduces a bound on right-handed neutrino mass which remained unrestricted by neutrino oscillation data.