Seesaw models with leptonic symmetries allow right-handed (RH) neutrino masses at the electroweak scale, or even lower, at the same time having large Yukawa couplings with the Standard Model leptons, thus yielding observable effects at current or near-future lepton-flavour-violation (LFV) experiments. These models have been previously considered also in connection to low-scale leptogenesis, but the combination of observable LFV and successful leptogenesis has appeared to be difficult to achieve unless the leptonic symmetry is embedded into a larger one. In this paper, instead, we follow a different route and consider a possible connection between large LFV rates and Dark Matter (DM). We present a model in which the same leptonic symmetry responsible for the large Yukawa couplings guarantees the stability of the DM candidate, identified as the lightest of the RH neutrinos. The spontaneous breaking of this symmetry, caused by a Majoron-like field, also provides a mechanism to produce the observed relic density via the decays of the latter. The phenomenological implications of the model are discussed, finding that large LFV rates, observable in the near-future $μ\to e$ conversion experiments, require the DM mass to be in the keV range. Moreover, the active-neutrino coupling to the Majoron-like scalar field could be probed in future detections of supernova neutrino bursts.
Motivated by the recent Xenon1T result, we study a leptophilic flavour-dependent anomaly-free axion-like particle (ALP) and its effects on charged-lepton flavour violation (CLFV). We present two representative models. The first one considers that the ALP origins from the flavon that generates the charged-lepton masses. The second model assumes a larger flavour symmetry such that more general mixings in the charged-lepton are possible, while maintaining flavour-dependent ALP couplings. We find that a keV ALP explaining the Xenon1T result is still viable for lepton flavour violation and stellar …
We study the influence of lepton flavour asymmetries on the formation and the mass spectrum of primordial black holes. We estimate the detectability of their mergers with LIGO/Virgo and show that the currently published gravitational wave events may actually be described by a primordial black hole spectrum from non-zero asymmetries. We suggest to use gravitational-wave astronomy as a novel tool to probe how lepton flavour asymmetric the Universe has been before the onset of neutrino oscillations.
Lepton Flavour Eigenstates do not Exist if Neutrinos are Massive: `Neutrino Oscillations' Reconsidered
如果中微子是有质量的，那么所有标准模型过程的振幅中都不存在“轻子味本征态”。测量的$Γ(π\to e ν)/Γ(π\to μν)$和MNS矩阵示出排除这种状态的存在。不同味中微子的非相干产生改变了通常假设轻子味本征态产生的振荡相位。新的预测可以通过比较π介子和K介子衰变中中微子的“$ν_μ$消失”，在长线基实验中得到检验。
We study the impact of large lepton flavour asymmetries on the cosmic QCD transition. Scenarios of unequal lepton flavour asymmetries are observationally almost unconstrained and therefore open up a whole new parameter space for the cosmic QCD transition. We find that for large asymmetries the formation of a Bose-Einstein condensate of pions can occur and identify the corresponding parameter space. In the vicinity of the QCD transition scale, we express the pressure in terms of a Taylor expansion with respect to the complete set of chemical potentials. The Taylor coefficients rely on input fro…
Two-Higgs-doublet models with Minimal Flavour Violation
在两个希格斯偶极子模型中的树级味道变化中性电流可以通过保护味道或味道盲对称性的破坏来抑制，但只有第一个选择，通过应用最小味道违反假设来实现，在量子校正下是稳定的。此外，一个富含味盲相的具有最小味破坏的双Higgs二重态模型可以解释最近在Delta F = 2跃迁中发现的异常现象，即B_s混合中的CP破坏相以及S_s_K和S_s_K之间的张力。
