Neutrino masses and Baryogenesis via Leptogenesis in the Exceptional Supersymmetric Standard Model

[摘要] Neutrino oscillation experiments discover that (left-handed) neutrinos have masses much less than charged leptons and quarks in the Standard Model. One solution to the lightneutrino mass puzzle is the seesaw model where right-handed neutrinos are introduced with large Majorana masses. The heavy Majorana right-handed (RH) neutrinos lead to leptonnumber violation in the early universe. They decay into either leptons or anti-leptons via Yukawa couplings. The CP asymmetries of these decays result in lepton number asymmetry in the universe. The lepton number asymmetry can be converted into baryon number asymmetry via the electroweak sphaleron process. This mechanism explains thebaryon asymmetry of universe problem and is called leptogenesis.However, one finds that in order to generated enough baryon number in the universe, the reheating temperature, which is required to be of order of the lightest right-handedneutrino mass, has to be higher than ∼ 10^9 GeV. The high reheating temperature would lead to the over-produced gravitinos in the universe, contrasting with the present observation. We investigate leptogenesis in the Exceptional Supersymmetric Standard Model. We find that the extra Yukawa couplings would enhance the CP asymmetries of the RH neutrino decay drastically. And the evolution of lepton/baryon asymmetries is described by Boltzmann Equations. Numerical calculation of the Boltzmann Equations shows that a correct amount of baryon number in the universe can be achieved when the lightest right-handed neutrino mass is ∼ 10^7 GeV, and then the gravitino-over-production problem is avoided.

[发布机构] University:University of Glasgow;Department:School of Physics and Astronomy

[关键词] Neutrino, Leptogenesis, Baryogenesis, Supersymmetry, Beyond the Standard Model, Boltzmann Equations