Low-scale leptogenesis with three heavy neutrinos

Abstract

Leptogenesis induced by the oscillations of GeV-scale neutrinos provides a minimal and testable explanation of the baryon asymmetry of the Universe. In this work we extend previous studies invoking only two heavy neutrinos to the case of three heavy neutrinos. We find qualitatively new behaviour as a result of lepton number violating oscillations and decays, strong flavour effects in the washout and a resonant enhancement due to matter effects. An approximate global B −L symmetry (representing the difference of baryon and a generalised lepton number) can protect the light neutrino masses from large radiative corrections, while simultaneously providing the ingredients for the resonant enhancement of the lepton asymmetry due to thermal contributions to the heavy neutrino dispersion relations. This mechanism is particularly efficient for large heavy neutrino mixing angles near the current experimental limits, a regime in which leptogenesis is not feasible in the minimal scenario with two heavy neutrinos. In this new parameter regime, low-scale leptogenesis is testable by the LHC and other existing experiments.

Freeze-in leptogenesis with 3 right-handed neutrinos

“…1 the active-sterile mixing in the muon flavour as a function of the heavy neutrino mass, for the viable solutions reproducing both active neutrino parameters and the BAU. Similar results are obtained for the other flavours [1]. It is evident from Fig.…”

“…In this work we show that the SM extended with three right-handed neutrinos with masses below the electroweak scale can provide a simultaneous explanation for both neutrino masses (and lepton mixing) and the BAU, as observed, and that a relevant fraction of the resulting parameter space can be tested by already running experiments, including ATLAS, CMS, LHCb, NA62, T2K and Belle II, cf. [1] for further details.…”

New long-lived particle searches in heavy-ion collisions at the LHC

“…Light neutrino oscillation data and the baryon asymmetry of the universe can be explained in the entire white part of the plots in figures 5 and 9 if there are at least three flavors of heavy neutrinos [146]. 7 Heavy neutrinos in the mass range considered here can indirectly affect the 7 For two heavy neutrinos baryogenesis requires roughly ( U 2 10 −5 )( M /GeV ) < 1 [97,147,148] and is only possible for specific flavor mixing patterns [97,149,150].…”

“…7 Heavy neutrinos in the mass range considered here can indirectly affect the 7 For two heavy neutrinos baryogenesis requires roughly ( U 2 10 −5 )( M /GeV ) < 1 [97,147,148] and is only possible for specific flavor mixing patterns [97,149,150]. These restrictions are lifted for three or more right handed neutrino flavors [146]. production of sterile neutrino DM by generating chemical potentials that trigger a resonant enhancement of the DM production [151], but current studies suggest that the required magnitude of these potentials [152][153][154] can only be generated for mixing angles that are too small to be accessed by the searches we propose [107,108,155].…”

Kinetic equations for sterile neutrinos from thermal fluctuations

“…1 bodeker@physik.uni-bielefeld.de 2 dennis@physik.uni-bielefeld.de Leptogenesis through oscillations has been described by Boltzmann equations, and in the relativistic case with several flavors with generalizations thereof [8]. The momentum spectrum of sterile neutrinos is non-thermal and it can be important to keep the full momentum dependence [9], but for parameter-space scans usually momentum space averages are considered (for recent work see, e.g., [10,11]). There have been various approaches which start from first principles to avoid some ad-hoc assumptions inherent in the Boltzmann equation, and to systematically include medium effects [12][13][14][15].…”