May 10, 2010
We propose a resonant leptogenesis scenario in a U(1)_{B-L} gauge extension of the standard model to generate large lepton asymmetries for cosmological baryon asymmetry and dark matter. After B-L number is spontaneously broken, inflaton can pick up a small vacuum expectation value for the mass splits of three pairs of quasi-degenerately heavy Majorana neutrinos and the masses of three sterile neutrinos. With thermal mass effects of sphalerons, the observed small baryon asymmetry can be converted from large lepton asymmetries of individual flavors although total lepton asymmetry is assumed zero. The mixing between sterile and active neutrinos is elegantly suppressed by the heavy Majorana neutrinos. Before the active neutrinos start their strong flavor conversions, the sterile neutrinos as warm dark matter can be produced by resonant active-sterile neutrino oscillations to reconcile X-ray and Lyman-\alpha bounds. Small neutrino masses are naturally realized by seesaw contributions from the heavy Majorana neutrinos and the sterile neutrinos.
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May 21, 2018
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After a brief discussion of baryon and lepton number nonconservation, we review the status of thermal leptogenesis with GUT scale neutrino masses, as well as low scale alternatives with keV neutrinos as dark matter and heavy neutrino masses within the reach of the LHC. Recent progress towards a full quantum mechnical description of leptogenesis is described with resonant leptogenesis as an application. Finally, cosmological B-L breaking after inflation is considered as origin...
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We investigate the resonant leptogenesis scenario in the minimally $U(1)_{B-L}$ extended standard model with minimal flavor violation. In our model, the $U(1)_{B-L}$ gauge symmetry is broken at the TeV scale and standard model singlet neutrinos gain Majorana masses of order TeV. In addition, we introduce a flavor symmetry on the singlet neutrinos at a scale higher than TeV. The flavor symmetry is explicitly broken by the neutrino Dirac Yukawa coupling, which induces splitting...
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We propose a model with an $U(1)_{B-L}$ gauge symmetry, in which small neutrino masses, dark matter and the matter-antimatter asymmetry in the Universe can be simultaneously explained. In particular, the neutrino masses are generated radiatively, while the matter-antimatter asymmetry is led by the leptogenesis mechanism, at TeV scale. We also explore allowed regions of the model parameters and discuss some phenomenological effects including lepton flavor violating processes.
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The cosmological baryon asymmetry is closely related to neutrino properties due to the non-perturbative sphaleron processes in the high-temperature symmetric phase of the standard model. We review some aspects of this connection with emphasis on cosmological bounds on neutrino masses, leptogenesis and possible implications for dark matter.
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We investigate the resonant leptogenesis scenario in the minimal B-L extended standard model(SM) with the B-L symmetry breaking at the TeV scale. Through detailed analysis of the Boltzmann equations, we show how much the resultant baryon asymmetry via leptogenesis is enhanced or suppressed, depending on the model parameters, in particular, the neutrino Dirac Yukawa couplings and the TeV-scale Majorana masses of heavy degenerate neutrinos. In order to consider a realistic case...
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In order to address the baryon asymmetry in the Universe one needs to understand the origin of baryon (B) and lepton (L) number violation. In this article, we discuss the mechanism of baryogenesis via leptogenesis to explain the matter-antimatter asymmetry in theories with spontaneous breaking of baryon and lepton number. In this context, a lepton asymmetry is generated through the out-of-equilibrium decays of right-handed neutrinos at the high-scale, while local baryon numbe...
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In this work we study a classically scale invariant extension of the Standard Model that can explain simultaneously dark matter and the baryon asymmetry in the universe. In our set-up we introduce a dark sector, namely a non-Abelian SU(2) hidden sector coupled to the SM via the Higgs portal, and a singlet sector responsible for generating Majorana masses for three right-handed sterile neutrinos. The gauge bosons of the dark sector are mass-degenerate and stable, and this make...