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Probing the seesaw mechanism with neutrino data and leptogenesis | Evgeny Kh. Akhmedov
; Michele Frigerio
; Alexei Yu. Smirnov
; | Date: |
29 May 2003 | Journal: | JHEP 0309 (2003) 021 | Subject: | hep-ph astro-ph hep-ex | Affiliation: | ICTP, Trieste), Michele Frigerio (INFN & SISSA, Trieste), Alexei Yu. Smirnov (ICTP, Trieste & INR, Moscow | Abstract: | In the framework of the seesaw mechanism with three heavy right-handed Majorana neutrinos and no Higgs triplets we carry out a systematic study of the structure of the right-handed neutrino sector. Using the current low-energy neutrino data as an input and assuming hierarchical Dirac-type neutrino masses $m_{Di}$, we calculate the masses $M_i$ and the mixing of the heavy neutrinos. We confront the inferred properties of these neutrinos with the constraints coming from the requirement of a successful baryogenesis via leptogenesis. In the generic case the masses of the right-handed neutrinos are highly hierarchical: $M_i propto m_{Di}^2$; the lightest mass is $M_1 approx 10^3 - 10^6$ GeV and the generated baryon-to-photon ratio $eta_Blesssim 10^{-14}$ is much smaller than the observed value. We find the special cases which correspond to the level crossing points, with maximal mixing between two quasi-degenerate right-handed neutrinos. Two level crossing conditions are obtained: ${m}_{ee}approx 0$ (1-2 crossing) and $d_{12}approx 0$ (2-3 crossing), where ${m}_{ee}$ and $d_{12}$ are respectively the 11-entry and the 12-subdeterminant of the light neutrino mass matrix in the basis where the neutrino Yukawa couplings are diagonal. We show that sufficient lepton asymmetry can be produced only in the 1-2 crossing where $M_1 approx M_2 approx 10^{8}$ GeV, $M_3 approx 10^{14}$ GeV and $(M_2 - M_1)/ M_2 lesssim 10^{-5}$. | Source: | arXiv, hep-ph/0305322 | Services: | Forum | Review | PDF | Favorites |
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