Electroweak naturalness in the three-flavor type I seesaw model and implications for leptogenesis

• Published in: Physical review. D, Particles, fields, gravitation, and cosmology Vol. 91; no. 7
• Main Authors: Clarke, Jackson D., Foot, Robert, Volkas, Raymond R.
• Format: Journal Article
• Language: English
• Published: 10-04-2015
• Subjects: Cosmology; Decoupling; Electroweak model; Flavor (particle physics); Gravitation; Mathematical models; Neutrinos
• ISSN: 1550-7998; 1550-2368
• DOI: 10.1103/PhysRevD.91.073009

In the type I seesaw model, the naturalness requirement that corrections to the electroweak mu parameter not exceed 1 TeV results in a rough bound on the lightest right-handed neutrino mass, M sub(N1) [<, ~] 3 x 10 super(7) GeV. In this paper we derive generic bounds applicable in any three-flavor type I seesaw model. We find M sub(N1) [<, ~] 4 x 10 super(7) GeV and M sub(N2) [<, ~] 7 x 10 super(7) GeV. In the limit of one massless neutrino, there is no naturalness bound on M sub(N3) in the Poincare protected decoupling limit. Our results confirm that no type I seesaw model can explain the observed neutrino masses and baryogenesis via hierarchical (N sub(1) -, N sub(2)-, or N sub(3)-dominated) thermal leptogenesis while remaining completely natural.