Revising Limits on Neutrino-Majoron Couplings

Abstract

Any theory that have a global spontaneously broken symmetry will imply the existence of very light neutral bosons or massless bosons (sometimes called Majorons). For most of these models we have neutrino-Majoron couplings, that appear as additional branching ratios in decays of mesons and leptons. Here we present an updated limits on the couplings between the electron, muon and tau neutrinos and Majorons. For such we analyze the possible effects of Majoron emission in both meson and lepton decays. In the latter we also include an analysis of the muon decay spectrum. Our results are $|g_{eα}|^{2}<5.5x10^{-6}$, $|g_{μα}|^{2}<4.5x10^{-5}$ and $|g_{τα}|^{2}<5.5x10^{-2}$ at 90 % C. L., where $α=e,μ,τ$.