A 4-neutrino model with a Higgs triplet

Abstract

We take as a starting point the Gelmini -Roncadelli model enlarged by a term with explicit lepton number violation in the Higgs potential and add a neutrino singlet field coupled via a scalar doublet to the usual leptons. This scenario allows us to take into account all three present indications in favour of neutrino oscillations provided by the solar, atmospheric and LSND neutrino oscillation experiments. Furthermore, it suggests a model which reproduces naturally one of the two 4-neutrino mass spectra favoured by the data. In this model the solar neutrino problem is solved by large mixing MSW ν e → ν τ transitions and the atmospheric neutrino problem by transitions of ν µ into a sterile neutrino.

The 2+2 and 3+1 four-family neutrino mixing at the neutrino factory

“…• The 3+1 scheme This scheme is only marginally allowed (a recent study [24] shows that it is compatible with the experimental data at the 99 % CL only). However, it is a natural extension of the three-family model.…”

Neutrino mass hierarchy and Majorana CP phases within the Higgs triplet model at the LHC

“…Assuming that all other mass parameters in the potential are of the electroweak scale v, the minimisation of the potential leads to the relation for the triplet VEV v T ∼ µ, see e.g. [11]. The hierarchy µ ≪ v may find an explanation for example through extra dimensions [12].…”

Physical reach of a neutrino factory in the 2+2 and 3+1 four-family scenario

“…There are two very different classes of spectra with four massive neutrinos: two pairs of almost degenerate neutrinos divided by the large LSND mass gap (the 2+2 scheme); or three almost degenerate neutrinos and an isolated fourth one (the 3+1 scheme). The former gave a better fit, as was shown in [2], but the recent SNO results [3] will certainly restrict the allowed parameter region. The latter is at present only marginally compatible with the data [4].…”