Soft leptogenesis in the inverse seesaw model
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Garayoa, Julia; González García, Mª Concepción; Rius Dionis, Nuria
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Aquest document és un/a article, creat/da en: 2007
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We consider leptogenesis induced by soft supersymmetry breaking terms ('soft leptogenesis'), in the context of the inverse seesaw mechanism. In this model there are lepton number (L) conserving and L-violating soft supersymmetry-breaking B-terms involving the singlet sneutrinos which, together with the - generically small - L-violating parameter responsible of the neutrino mass, give a small mass splitting between the four singlet sneutrino states of a single generation. In combination with the trilinear soft supersymmetry breaking terms they also provide new CP violating phases needed to generate a lepton asymmetry in the singlet sneutrino decays. We obtain that in this scenario the lepton asymmetry is proportional to the L-conserving soft supersymmetry-breaking B-term, and it is not suppressed by the L-violating parameters. Consequently we find that, as in the standard see-saw case, this mechanism can lead to sucessful leptogenesis only for relatively small value of the relevant soft bilinear coupling. The right-handed neutrino masses can be sufficiently low to elude the gravitino problem. Also the corresponding Yukawa couplings involving the lightest of the right-handed neutrinos are constrained to be Sigma vertical bar Y-1k vertical bar(2) less than or similar to 10(-7) which generically implies that the neutrino mass spectrum has to be strongly hierarchical
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