Freiburg 2008 – scientific programme
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T: Fachverband Teilchenphysik
T 18: Neutrinophysik (Theorie)
T 18.6: Talk
Friday, March 7, 2008, 15:15–15:30, Peterhof-HS 4
Effects of Lightest Neutrino Mass in Leptogenesis — Emiliano Molinaro1,2, Serguey Petcov1,2, •Tetsuo Shindou3, and Yasutaka Takanishi1,2 — 1SISSA, Trieste, Italy — 2INFN sezione di Trieste, Trieste, Italy — 3DESY Theory Group, Hamburg, Germany
The effects of the lightest neutrino mass in “flavoured” leptogenesis are investigated in the case when the CP-violation necessary for the generation of the baryon asymmetry of the Universe is due exclusively to the Dirac and/or Majorana phases in the neutrino mixing matrix U. The type I see-saw scenario with three heavy right-handed Majorana neutrinos having hierarchical spectrum is considered. The “orthogonal” parametrisation of the matrix of neutrino Yukawa couplings, which involves a complex orthogonal matrix R, is employed. Results for light neutrino mass spectrum with normal and inverted ordering (hierarchy) are obtained. It is shown, in particular, that if the matrix R is real and CP-conserving and the lightest neutrino mass m3 in the case of inverted hierarchical spectrum lies the interval 5 × 10−4eV < m3 <7× 10−3eV, the predicted baryon asymmetry can be larger by a factor of arround 100 than the asymmetry corresponding to negligible m3∼ 0. As consequence, we can have successful thermal leptogenesis for 5 × 10−6eV < m3 < 5 × 10−2eV even if R is real and the only source of CP-violation in leptogenesis is the Majorana and/or Dirac phase(s) in U.