Leptogenesis and neutrino observables

• Grant number: 25/02932-5
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: May 01, 2025
• End date: April 30, 2026
• Field of knowledge: Physical Sciences and Mathematics - Physics - Elementary Particle Physics and Fields
• Principal Investigator: Chee Sheng Fong
• Grantee: Luiza Nunes Brito
• Host Institution: Centro de Ciências Naturais e Humanas (CCNH). Universidade Federal do ABC (UFABC). Ministério da Educação (Brasil). Santo André , SP, Brazil
• Associated research grant: 19/11197-6 - Precision test of baryogenesis, AP.JP

Abstract

In type-I seesaw model, the parameters for leptogenesis are tightly connected to low energy neutrino observables. Using Casas-Ibarra parametrization, it becomes apparent that leptogenesis can also depend on six additional high energy parameters. However, if leptogenesis were to occur at temperature greater than 10^{12} GeV and the heavy fermion mass spectrum is hierarchical, there is an upper bound on the amount of CP violation required for leptogenesis (also known as the Davidson-Ibarra bound) which only depends on neutrino observables. Below this temperature where lepton flavor effects become relevant, the bound does no longer hold though certain relations with neutrino observables remain. At even lower temperature T ¿ 10^6 GeV, the washout from scatterings become relevant and will need to be taken into account.