A potential scenario for Majorana neutrino detection at future lepton colliders

Yang Zhang,Bin Zhang

doi:10.1007/jhep02(2019)175

Abstract

The existence of Majorana neutrinos must lead to lepton-number violating processes, and the Majorana nature of neutrinos can only be experimentally verified via lepton-number violating processes. We study an approach to search for Majorana neutrinos at future electron-positron colliders by exploiting this feature. We investigate ΔL = 2 like-sign dilepton production and find that lepton colliders with different center-of-mass (c.m.) energies have comparative advantages in resonant production of a Majorana neutrino in both light and heavy neutrino mass range. At the future Circular Electron-Positron Collider (CEPC), with 250 GeV c.m. energy and 5 ab−1 integrated luminosity, we find that there could be more significant sensitivity for resonant production of a Majorana neutrino in the mass range of 30-50 GeV than previous results at LEP2 or LHC. At the 1 TeV ILC with 1 ab−1 integrated luminosity, the sensitivity can be improved for neutrino mass in the range of 450-600 GeV.

Highlights

Models and mixing parametersWe begin our discussion by describing two basic models, to show how Majorana neutrinos fit into the big picture of the SM particles
JHEP02(2019)175 and 1600 GeV [42,43,44,45,46,47]
For neutrino masses in the range of 30–50 GeV where the Circular Electron-Positron Collider (CEPC) has the best sensitivity, Sμμ can be probed to about 3 × 10−6 at a 2σ level and 7 × 10−6 at a 5σ level

Summary

Models and mixing parameters

We begin our discussion by describing two basic models, to show how Majorana neutrinos fit into the big picture of the SM particles. For MN MW , MZ, MH , the decay branching ratios are Br( −W +) ≈ Br(ν Z) ≈ Br(ν H) ≈ 25% Another way to incorporate Majorana neutrinos is through SU(2)L lepton triplets which is known as the Type III Seesaw mechanism [68,69,70]. In addition to the mixing between charged triplet leptons Σ±L and SM charged leptons e, μ, τ , which is special to the Type III Seesaw mechanism, Σ0Rc has the same Yukawa coupling and mass term as the right-handed neutrino of the Type I Seesaw above. A comprehensive discussion regarding the upper bounds on the mixing elements from all kinds of experimental and prospective studies can be found in [70, 88,89,90,91]

Collider signatures

Phenomenological Analysis at the CEPC

Phenomenological analysis at the ILC

Summary and conclusions