Heavy Neutrino Oscillations Research Articles

Exploring CP-violation, via heavy neutrino oscillations, in rare B meson decays at Belle II

In this article we study the rare B-meson decay via two on-shell almost-degenerate Majorana Heavy Neutrinos, into two charged leptons and two pseudoscalar mesons (B^{pm } rightarrow D^0 ell ^{pm }_1 ell ^{pm }_2 pi ^{mp }). We consider the scenario where the heavy neutrino masses are sim 2 GeV and the heavy-light mixing coefficients are |B_{ell N}|^2 sim 10^{-5}, and evaluate the possibility to measure the CP-asymmetry at Belle II. We present some realistic conditions under which the asymmetry could be detected.

Exploring CP-violating heavy neutrino oscillations in rare tau decays at Belle II

In this work, we study the lepton number violating tau decays via two intermediate on-shell Majorana neutrinos Nj into two charged pions and a charged lepton τ±→π±Nj→π±π±ℓ∓. We consider the scenario where the heavy neutrino masses are within 0.5 GeV≤MN≤1.5 GeV. We evaluated the possibility to measure the modulation of the decay width along the detector length for these processes at tau factories, such as Belle II. We study some realistic conditions which could lead to the observation of this phenomenon at futures τ factories.

Measuring the heavy neutrino oscillations in rare W boson decays at the Large Hadron Collider

Majorana neutrinos in the seesaw model can have sizable mixings through which they can be produced at the Large Hadron Collider (LHC) and show a remarkable lepton number violating (LNV) signature. In this article we study the LNV decay of the W boson via two almost degenerate heavy on-shell Majorana neutrinos Nj, into three charged leptons and a light neutrino. We consider the scenario where the heavy neutrino masses are within 1 GeV . We evaluated the possibility to measure a LNV oscillation process in such a scenario, namely, the modulation of the quantity for the process at the LHC where . L is the distance within the detector between the two vertices of the process. We found out some realistic conditions under which such a modulation could be probed at the LHC.

CP violating effects in heavy neutrino oscillations: implications for colliders and leptogenesis

Two of the important implications of the seesaw mechanism are: (i) a simple way to understand the small neutrino masses, and (ii) the origin of matter-anti-matter asymmetry in the universe via the leptogenesis mechanism. For TeV-scale seesaw models, successful leptogenesis requires that the right-handed neutrinos (RHNs) must be quasi-degenerate and if they have CP violating phases, they also contribute to the CP asymmetry. We investigate this in the TeV-scale left-right models for seesaw and point out a way to probe the quasi-degeneracy possibility with CP violating mixings for RHNs in hadron colliders using simple observables constructed out of same-sign dilepton charge asymmetry (SSCA). In particular, we isolate the parameter regions of the model, where the viability of leptogenesis can be tested using the SSCA at the Large Hadron Collider, as well as future 27 TeV and 100 TeV hadron colliders. We also independently confirm an earlier result that there is a generic lower bound on the WR mass of about 10 TeV for leptogenesis to work.

Probing leptogenesis at future colliders

We investigate the question whether leptogenesis, as a mechanism for explaining the baryon asymmetry of the universe, can be tested at future colliders. Focusing on the minimal scenario of two right-handed neutrinos, we identify the allowed parameter space for successful leptogenesis in the heavy neutrino mass range between 5 and 50 GeV. Our calculation includes the lepton flavour violating contribution from heavy neutrino oscillations as well as the lepton number violating contribution from Higgs decays to the baryon asymmetry of the universe. We confront this parameter space region with the discovery potential for heavy neutrinos at future lepton colliders, which can be very sensitive in this mass range via displaced vertex searches. Beyond the discovery of heavy neutrinos, we study the precision at which the flavour-dependent active-sterile mixing angles can be measured. The measurement of these mixing angles at future colliders can test whether a minimal type I seesaw mechanism is the origin of the light neutrino masses, and it can be a first step towards probing leptogenesis as the mechanism of baryogenesis. We discuss how a stronger test could be achieved with an additional measurement of the heavy neutrino mass difference.

Majorana Neutrino Oscillations in Vacuum

In the context of a type I seesaw scenario which leads to get light left-handed and heavy right-handed Majorana neutrinos, we obtain expressions for the transition probability densities between two flavor neutrinos in the cases of left-handed and right-handed neutrinos. We obtain these expressions in the context of an approach developed in the canonical formalism of Quantum Field Theory for neutrinos which are considered as superpositions of mass-eigenstate plane waves with specific momenta. The expressions obtained for the left-handed neutrino case after the ultra-relativistic limit is taking lead to the standard probability densities which describe light neutrino oscillations. For the right-handed neutrino case, the expressions describing heavy neutrino oscillations in the non-relativistic limit are different respect to the ones of the standard neutrino oscillations. However, the right-handed neutrino oscillations are phenomenologically restricted as is shown when the propagation of heavy neutrinos is considered as superpositions of mass-eigenstate wave packets.