Can heavy neutrinos dominate neutrinoless double beta decay?

Abstract

We study whether a dominant contribution to neutrinoless double beta decay coming from extra heavy degrees of freedom, introduced to generate the light neutrino masses, can dominate over the light neutrino contribution. It has been shown that this may occur at tree-level if the light neutrino contribution partially cancels out. Here we focus on this case, specifically in the context of type-I seesaw models paying special attention to the one-loop corrections to light neutrino masses, their contribution to the process and correlation with the heavy sector. We perform a general analysis without restricting the study to any particular region of the parameter space, although interesting limits associated with inverse and extended seesawlike models are discussed in more detail. It turns out that the heavy neutrinos can dominate the process only in those limits. For the inverse seesaw limit, we find a very constrained allowed region of the parameter space, with heavy neutrino masses around 5 GeV. The extended seesaw case allows for a larger region, but in general, a hierarchical spectrum of heavy neutrinos with masses above and below ∼ 100 MeV is required.

Muon conversion to electron in nuclei in type-I seesaw models

“…(4.6), (4.7), (5.6) and (5.7). However, the price to obtain measurable flavour-changing rates with hierarchical spectra is to induce unacceptably large neutrino masses, disregarding eventual large fine-tuning between the various parameters 4 (which anyway would be destabilized by unacceptably large radiative contributions to neutrino masses [46]). Moreover, the heavy right-handed neutrino contribution to neutrinoless double beta decay can be in contradiction with the current bound [47][48][49], especially for low righthanded neutrino masses below a few tens of GeV.…”

Improving electro-weak fits with TeV-scale sterile neutrinos

“…In particular, the new states can contribute to the amplitude of the neutrinoless double-beta decay [35][36][37][38][39] and induce rare charged lepton decays [40,41]. Furthermore, they can affect the electro-weak precision observables (EWPOs) via tree-level as well as loop contributions and thus provide an explanation for anomalies in the experimental data.…”

Radiative neutrino mass generation linked to neutrino mixing and0νββ-decay predictions

“…This is in contrast with more conventional scenarios of neutrino mass generation, such as seesaw models [72]. We note that if LNV physics couples directly to quarks, or if the SM gauge group is extended, it is also generically possible for the short-range contributions to 0νββ decay to dominate (see Ref.…”