Lepton Number Violation: Seesaw Models and Their Collider Tests

Abstract

The Majorana nature of neutrinos is strongly motivated from the theoretical and phenomenological point of view. A plethora of neutrino mass models, known collectively as Seesaw models, exist that could generate both a viable neutrino mass spectrum and mixing pattern. They can also lead to rich, new phenomenology, including lepton number non-conservation as well as new particles, that may be observable at collider experiments. It is therefore vital to search for such new phenomena and the mass scale associated with neutrino mass generation at high energy colliders. In this review, we consider a number of representative Seesaw scenarios as phenomenological benchmarks, including the characteristic Type I, II, and III Seesaw mechanisms, their extensions and hybridizations, as well as radiative constructions. We present new and updated predictions for analyses featuring lepton number violation and expected coverage in the theory parameter space at current and future colliders. We emphasize new production and decay channels, their phenomenological relevance and treatment across different facilities in e + e − , e − p, and pp collisions, as well as the available Monte Carlo tools available for studying Seesaw partners in collider environments.

Electric dipole moments in the minimal scotogenic model

“…For instance, at colliders, there are several possible signatures of lepton number violation [14][15][16][17][18][19][20]. As pointed out in several analyses, neutrino Majorana phases can also give rise to non-vanishing contributions to charged lepton electric dipole moments (EDMs) [21]; in particular, the computation of EDMs in the presence of right-handed neutrinos (like in the Type-I seesaw model) has been addressed in refs.…”

Probing doubly and singly charged Higgs bosons at the pp collider HE-LHC

“…Note that, other than the pair-production by DY, the photon fusion can also contribute to the pair-production of doubly charged Higgs. It has been pointed out in [52], that for 13 TeV, the channel contributes at most 10% to the pair-production of doubly charged Higgs states. However, there are different issues, regarding large uncertainties in PDFs.…”

Doubly charged Higgs boson production at hadron colliders

“…For comprehensive reviews, we refer to Refs. [14,36]. Current experimental searches by both the ATLAS and CMS collaborations report 95% confidence level (CL) exclusion limits on triplet scalar masses up to about 400 GeV in multileptonic channels [37,38] and about 200 GeV in bosonic channels [39], assuming a degenerate mass spectrum.…”