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Baryogenesis through leptogenesis

Riccardo Barbieri, Paolo Creminelli, Alessandro Strumia, Nikolaos Tetradis

Abstract

Baryogenesis by heavy-neutrino decay and sphaleron reprocessing of both baryon and lepton number is reconsidered, paying special attention to the flavour structure of the general evolution equations and developing an approximate but sufficiently accurate analytic solution to the prototype evolution equation. Two different models of neutrino masses are examined, based on an Abelian U(1) or a non-Abelian U(2) family symmetry. We show that a consistent picture of baryogenesis can emerge in both cases, although with significant differences.

Baryogenesis through leptogenesis

Abstract

Baryogenesis by heavy-neutrino decay and sphaleron reprocessing of both baryon and lepton number is reconsidered, paying special attention to the flavour structure of the general evolution equations and developing an approximate but sufficiently accurate analytic solution to the prototype evolution equation. Two different models of neutrino masses are examined, based on an Abelian U(1) or a non-Abelian U(2) family symmetry. We show that a consistent picture of baryogenesis can emerge in both cases, although with significant differences.

Paper Structure

This paper contains 17 sections, 45 equations, 1 figure.

Table of Contents

  1. color cmyk 1. 1. 0 0.5 Introductioncolor cmyk 0 0 0 1.
  2. color cmyk 1. 1. 0 0.5 General setting of the problemcolor cmyk 0 0 0 1.
  3. color cmyk 1. 1. 0 0.5 Flavour properties of leptogenesis by heavy neutrino decaycolor cmyk 0 0 0 1.
  4. $T^* \approx M_1 \,\hbox{$>$$\sim$}\, 10^{11\div 12} \,{\rm GeV}$
  5. $10^9 \,{\rm GeV} \,\hbox{$<$$\sim$}\,\: T^* \approx M_1 \:\,\hbox{$<$$\sim$}\, 10^{11\div 12} \,{\rm GeV}$
  6. $T^* \approx M_1 \,\hbox{$<$$\sim$}\, 10^9 \,{\rm GeV}$
  7. color cmyk 1. 1. 0 0.5 Approximate analytic solutions of the Boltzmann equationscolor cmyk 0 0 0 1.
  8. color cmyk 1. 1. 0 0.5 Baryogenesis in specific models of neutrino massescolor cmyk 0 0 0 1.
  9. The U(1) model
  10. The U(2) model
  11. color cmyk 1. 1. 0 0.5 Conclusionscolor cmyk 0 0 0 1.
  12. Acknowledgments
  13. color cmyk 1. 1. 0 0.5 The explicit form of $N_1$ decay amplitudecolor cmyk 0 0 0 1.
  14. color cmyk 1. 1. 0 0.5 Approximate solutions of Boltzmann equations for leptogenesiscolor cmyk 0 0 0 1.
  15. The Boltzmann equation for the $N_1$ abundance
  16. ...and 2 more sections

Figures (1)

  • Figure 1: Contour plot of the efficiency factor $\eta$ of leptogenesis in the SM as function of $(\widetilde{m}_1,M_1$). The $\Delta L=2$ interactions not mediated by $N_1$ have been computed assuming $m_{\nu_3}= \max(\widetilde{m}_1,(3r~10^{-3})^{1/2}\,{\rm eV})$ and assuming that their flavour structure gives the weakest washing ($X=1$) in fig. \ref{['fig:Ex']}a, and the strongest washing ($X=m_{\nu_3}^2/\widetilde{m}_1^2$) in fig. \ref{['fig:Ex']}b. Continuous (dashed) lines assume thermal (zero) initial abundance of $N_1$.