Systematic approach to Δ L = 1 processes in thermal leptogenesis

Solving the Kadanoff-Baym (KB) equations in a different method from our previous analysis, we obtain the CP violating parameter ε in the thermal resonant leptogenesis without assuming smallness of the off-diagonal Yukawa couplings. For that purpose, we first derive a kinetic equation for density matrix of RH neutrinos with almost degenerate masses M i (i = 1, 2) ∼ M . If the deviation from thermal equilibrium is small, the differential equation is reduced to a linear algebraic equation and the density matrix can be solved explicitly in terms of the time variation of (local) equilibrium distribution function. The obtained CP-violating parameter ε i is proportional to an enhancement factorwith the previous analysis. The decay width can be determined systematically by the 1PI self-energy of the RH neutrinos in the 2PI formalism.

Section: Jhep08(2014)043mentioning

confidence: 99%

Coherent flavour oscillation and CP violating parameter in thermal resonant leptogenesis

Iso

Shimada

2014

“…The thermal mass and width are given by m ,φ ∼ gT , Γ ,φ ∼ g 2 T where g is the SM gauge coupling g. The effects of the thermal plasma play very important roles, and are systematically investigated in [68,69]. For example, the thermal mass of the Higgs becomes larger than the RH neutrino masses at very high temperature.…”

Section: Jhep04(2014)062mentioning

confidence: 99%

“…The effects of scattering can be taken into account 4 by considering the next simplest diagram of figure 5. A systematical study of the KB equation including the scattering effects is given in [68,69].…”

Section: Jhep04(2014)062mentioning

confidence: 99%

“…Using this method, one can systematically take into account quantum interference, finite temperature and finite density effects. 1 The method was intensively used in the leptogenesis in various papers [58]- [69]. In the resonant leptogenesis, since the quantum interference effect is crucial to the evaluation of the CP -violating parameter, we can expect importance of such a full-quantum mechanical formulation based on the KB equations.…”

Section: Jhep04(2014)062 1 Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Kadanoff-Baym approach to the thermal resonant leptogenesis

Iso

Shimada

Yamanaka

2014

Using the non-equilibrium Green function method (Kadanoff-Baym equations) in the expanding universe, we investigate evolution of the lepton number asymmetry when the right-handed (RH) neutrinos have almost degenerate massesThe resonantly enhanced CP -violating parameter ε i associated with the decay of the RH neutrino N i is obtained under an assumption that the off-diagonal component of the Yukawa coupling is smaller than the diagonal one. It is proportional to an enhancement factor (The result is consistent with the previous result obtained by Garny et al., in a constant background with an out-of-equilibrium initial state. We discuss the origin of such a regulator, and why it is not like R ij = M i Γ i − M j Γ j .

“…and the inclusion of quantum statistical factors[95][96][97][98] which typically introduces an O (10%) error[27,[99][100][101]. To solve the density matrix equations we use the Python interface[102] to the LSODA algorithm[103] that is available in Scientific Python[104].…”

mentioning

confidence: 99%

Leptogenesis from low energy CP violation

Moffat

Pascoli

Petcov

et al. 2019

We revisit the possibility of producing the observed baryon asymmetry of the Universe via thermal leptogenesis, where CP violation comes exclusively from the low-energy phases of the neutrino mixing matrix. We demonstrate the viability of thermal flavoured leptogenesis across seven orders of magnitude 10 6 < T (GeV) < 10 13 , using modern numerical machinery, where the lower bound can be reached only if flavour effects are taken into account and its value depends on the allowed degree of cancellation between the tree-level and radiative contributions to the light neutrino masses. At very high scales T 10 12 GeV , we clarify that thermal leptogenesis is sensitive to the low-energy phases, in contradiction with what is usually claimed in the literature. In particular we demonstrate that Majorana-phase leptogenesis is in general viable while Dirac-phase leptogenesis requires some level of fine-tuning.