Phenomenology of the Neutrino-Mass-Giving Higgs Triplet and the Low-Energy Seesaw Violation of Lepton Number

Ernest Ma; Martti Raidal; Utpal Sarkar

doi:10.1016/S0550-3213(01)00416-3

paper

Phenomenology of the Neutrino-Mass-Giving Higgs Triplet and the Low-Energy Seesaw Violation of Lepton Number

arXiv:hep-ph/0012101 · doi:10.1016/S0550-3213(01)00416-3

Abstract

Small realistic Majorana neutrino masses can be generated via a Higgs triplet $(ξ^{++}, ξ^{+}, ξ^{0})$ without having energy scales larger than $M_{*} = O (1)$ TeV in the theory. The large effective mass scale $Λ$ in the well-known seesaw neutrino-mass operator $Λ^{- 1} (LL ΦΦ)$ is naturally obtained with $Λ \sim M_{*}^{2} / μ,$ where $μ$ is a {\it small} scale of lepton-number violation. In theories with large extra dimensions, the smallness of $μ$ is naturally obtained by the mechanism of ``shining'' if the number of extra dimensions $n \geq 3.$ We study here the Higgs phenomenology of this model, where the spontaneous violation of lepton number is treated as an external source from extra dimensions. The observable decays $ξ^{++} \to l_{i}^{+} l_{j}^{+}$ will determine directly the magnitudes of the ${ij}$ elements of the neutrino mass matrix. The decays $ξ^{+} \to W^{+} J^{0}$ and $ξ^{0} \to Z J^{0}$ , where $J^{0}$ is the massless Goldstone boson (Majoron), are also possible, but of special importance is the decay $ξ^{0} \to J^{0} J^{0}$ which provides stringent constraints on the allowed parameter space of this model. Based on the current neutrino data, we also predict observable rates of $μ - e$ conversion in nuclei.

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Phenomenology of the Neutrino-Mass-Giving Higgs Triplet and the Low-Energy Seesaw Violation of Lepton Number

Abstract

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