Predictive leptogenesis from minimal lepton flavour violation

Abstract

A predictive Leptogenesis scenario is presented based on the Minimal Lepton Flavour Violation symmetry. In the realisation with three right-handed neutrinos transforming under the same flavour symmetry of the lepton electroweak doublets, lepton masses and PMNS mixing parameters can be described according to the current data, including a large Dirac CP phase. The observed matter-antimatter asymmetry of the Universe can be achieved through Leptogenesis, with the CP asymmetry parameter ε described in terms of only lepton masses, mixings and phases, plus two real parameters of the low-energy effective description. This is in contrast with the large majority of models present in the literature, where ε depends on several high-energy parameters, preventing a direct connection between low-energy observables and the baryon to photon ratio today. Recovering the correct amount of baryon asymmetry in the Universe constrains the Majorana phases of the PMNS matrix within specific ranges of values: clear predictions for the neutrinoless double beta decay emerge, representing a potential smoking gun for this framework.4 In Ref.[71], considering the SO(3) × CP version of MLFV, the equivalent of the coefficients c 1,2 have been shown to be generated by radiative corrections during the evolution of the Lagrangian parameters. Experiment Isotope |mee| [ eV] CUORE [188] 130 Te 0.073 ± 0.008 GERDA-II [189] 76 Ge 0.11 ± 0.01 LUCIFER [190] 82 Se 0.20 ± 0.02 MAJORANA D. [191] 76 Ge 0.13 ± 0.01 NEXT [192] 136 Xe 0.12 ± 0.01 AMoRE [193] 100 Mo 0.084 ± 0.008 nEXO [194] 136 Xe 0.011 ± 0.001 PandaX-III [195] 136 Xe 0.082 ± 0.009 SNO+ [196] 130 Te 0.076 ± 0.007 SuperNEMO [197] 82 Se 0.084 ± 0.008

Leptogenesis from low energy CP violation

“…There have been other works which have investigated the impact of low energy phases on the BAU. Indeed, CP conservation at the high-scale and CP violation at the low-scale in the context of leptogenesis can be theoretically motivated by minimal flavour violation [34,35], flavour symmetries [36][37][38] or a generalised CP symmetry [39][40][41]. Beyond the type I seesaw mechanism, there have been other studies which connect the Dirac phase, δ, with the BAU using an extended Higgs sector [42].…”

Data driven flavour model

“…Once the latter acquire background values, the strength of the effects induced by such operator gets suppressed by specific combinations of fermion masses and mixing angles and CP phases. As a consequence, the cut-off scale F , which would be constrained to be larger than hundreds or thousands of TeVs in the generic case [56], can be instead as low as few TeVs [43][44][45][46][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75]. Seeking to promote the MFV from a low-energy description to a well-defined theory even at higher energies, the spurions may be identified with dynamical scalar fields [47][48][49][50], dubbed flavons: any flavon insertion should be suppressed by a cut-off scale (larger than F ) that keeps the total mass dimension of any operator equal to d = 4.…”

Neutrino phenomenology from leptogenesis

“…The neutrinoless double beta parameter m ββ = i m i U 2 P M N S ei is found to lie between 0.001 eV and 0.02 eV, which is below the experimental bounds, set, for example, in [40]. 9 In Fig. 2 we show the evolution of the baryonic yield with the mass of the lightest neutrino: it is clear from the picture that only a tiny band of points leads to an efficient leptogenesis.…”