Abstract
The Standard Model (SM) is inadequate to explain the origin of tiny neutrino masses, the dark matter (DM) relic abundance and the baryon asymmetry of the Universe. In this work, to address all three puzzles, we extend the SM by a local U(1)_{B-L} gauge symmetry, three right-handed (RH) neutrinos for the cancellation of gauge anomalies and two complex scalars having non-zero U(1)_{B-L} charges. All the newly added particles become massive after the breaking of the U(1)_{B-L} symmetry by the vacuum expectation value (VEV) of one of the scalar fields phi _H. The other scalar field, phi _mathrm{DM}, which does not have any VEV, becomes automatically stable and can be a viable DM candidate. Neutrino masses are generated using the Type-I seesaw mechanism, while the required lepton asymmetry to reproduce the observed baryon asymmetry can be attained from the CP violating out of equilibrium decays of the RH neutrinos in TeV scale. More importantly within this framework, we study in detail the production of DM via the freeze-in mechanism considering all possible annihilation and decay processes. Finally, we find a situation when DM is dominantly produced from the annihilation of the RH neutrinos, which are at the same time also responsible for neutrino mass generation and leptogenesis.
Highlights
M232)1 with an unprecedented accuracy [3,4,5,6,7,8,9,10]
The Dirac mass terms involving both left chiral and right chiral neutrinos originate when the electroweak symmetry is spontaneously broken by the vacuum expectation value (VEV) of the Standard Model (SM) Higgs doublet φh, giving rise to a 3×3 complex matrix MD
As we have three RH neutrinos in the present model, we study the lepton asymmetry generated from the CP violating out of equilibrium decays of these heavy neutrinos at the early stage of the Universe
Summary
2 21 and m232) with an unprecedented accuracy [3,4,5,6,7,8,9,10]. Neutrinos are massless in the Standard Model (SM) of particle physics because in the SM there is no right-handed (RH) counterpart of the lefthanded (LH) neutrinos. Observation of neutrino-less double β decay [12,13,14,15,16,17] will confirm the Majorana nature of neutrinos and might provide important information as regards the Majorana phases, which could be the other source of CP violation in the leptonic sector, if the SM neutrinos are Majorana fermions Besides these unsolved problems in the neutrino sector, another well-known puzzle in recent times is the presence of dark matter (DM) in the Universe. The number density of the FIMP is negligible in the early Universe and increases when the FIMP is subsequently produced by the decays and annihilations of other particles to which it is coupled (very feebly) This process is generally known as freeze-in [34]. When the sphaleron processes are in thermal equilibrium (1012 GeV
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