Probing leptogenesis with GeV-scale sterile neutrinos at LHCb and Belle II

Abstract

We show that existing laboratory experiments have the potential to unveil the origin of matter by probing leptogenesis in the type-I seesaw model with three right-handed neutrinos and Majorana masses in the GeV range. The baryon asymmetry is generated by CP-violating flavour oscillations during the production of the right-handed neutrinos. In contrast to the case with only two right-handed neutrinos, no degeneracy in the Majorana masses is required. The right-handed neutrinos can be found in meson decays at BELLE II and LHCb.

Multilepton and lepton jet probes of sub-weak-scale right-handed neutrinos

“…Conversely, for M N m b − m c , the branching fraction of B → N is larger, but the lifetime is longer so that one must pay a severe penalty in rate to require the decay length to be 10 m. Combining this with the requirement of having sufficiently hard final states to reconstruct the lepton from B decay and the displaced vertex inside the muon spectrometer, we estimate the projected sensitivity to be worse than the current constraints. Thus, the lepton-jet final state from W decay is still the best way to search for RH neutrinos for M N m b with ATLAS/CMS, although direct searches of N production from B decays at B-factories and LHCb will have sensitivity in this mass range [36,91,92]. jets containing heavy-flavor hadrons.…”

Electron electric dipole moment in Inverse Seesaw models

“…Some of the latter scenarios may also provide a possible explanation to the dark matter relic density considering, putting forward a keV-scale sterile neutrino as a viable candidate [11,17], and/or to the BAU through leptogenesis (via neutrino oscillations) [18][19][20][21][22][23].…”

Impact of sterile neutrinos on nuclear-assisted cLFV processes

“…In addition to the three light (mostly active) neutrinos -whose masses are given by a type I seesaw relation -the neutral lepton spectrum further contains three heavy states (with masses m ν 4−6 ); should the latter three play a rôle regarding DM, or the BAU, their spectrum and couplings to the active states are subject to several (strong) conditions [43][44][45]. As previously done in [41], we parametrise the physical νMSM degrees of freedom in terms of its six mass eigenvalues, encoding all physical mixing angles and CP violating phases (Dirac and Majorana) in an effective 6 × 6 unitary mixing matrix U (which allows to readily implement the already well-established bounds on the νMSM parameter space).…”

“…As previously done in [41], we parametrise the physical νMSM degrees of freedom in terms of its six mass eigenvalues, encoding all physical mixing angles and CP violating phases (Dirac and Majorana) in an effective 6 × 6 unitary mixing matrix U (which allows to readily implement the already well-established bounds on the νMSM parameter space). 4 The angles θ lj , l = 1, 2, 3, j = 4, 5, 6 encode the active-sterile mixings, while the mixings between the sterile states are given by three additional angles θ 45,46,56 . The matrix U is further parametrised by 3 additional Majorana and 9 Dirac phases.…”