Compoiste Neutrinos and Double Beta Decay

Open Access
Publisher Website
Google Scholar
Abstract
Neutrinoless double beta decay (ββ)0ν occurs through the magnetic coupling of dimension five, λW(ν*)/mν*, among the excited electron neutrino ν*, electron, and W boson if ν* is a massive Majorana neutrino. If the coupling is not small, i.e., λW(ν*) > 1, the mass of the excited neutrino must not be less than the Z boson mass, mZ. Since ν* contributes in the (ββ)0ν decay as a virtual state, this decay will give an opportunity to explore the much heavier mass region of ν*. In this paper, we present the decay formula of (ββ)0ν decay through the ν* exchange and discuss the constraint on the coupling constant and the mass of the excited neutrino. By comparing the recent data for 76Ge, we find λW(ν*) (1 TeV/mν*)(mN/1 TeV)1/2 < 4.1·10−3, where mN is the Majorana mass of the excited electron neutrino. If mN = mν* and λW(ν*) > 1, we find the mass bound for the excited Majorana neutrino to be mν* > 5.9·104 TeV. In order to obtain a constraint on the composite scale Λ, we have to specify the model. For the mirror type and the homodoublet type models, λW(ν*)/mν* = f/(√2Λ), where f is the relative strength of gauge couplings. Then, we obtain Λ> 170 f(mN/1 TeV)1/2 TeV. For the sequential type model, λ/mν* = fυ/(√2Λ2), where υ is the vacuum expectation value of the doublet Higgs boson, i.e., υ=250 GeV. In this model, we find Λ> 6.6 f1/2(mN/1 TeV)1/4 TeV.
All Related Versions

This publication has 1 reference indexed in Scilit: