Supernova Bounds on Majoron-emitting decays of light neutrinos

TL;DR

This work analyzes how Majoron-emitting decays of light neutrinos operate in the dense supernova environment and how they alter the observed neutrino signal. By incorporating medium-induced modifications to decay and scattering rates, as well as neutrino oscillations, the authors derive robust bounds from SN1987A and forecast the sensitivity of future detectors like Super-Kamiokande and SNO for a galactic supernova. They find that a broad Majoron-neutrino coupling window $3\times10^{-7} \lesssim g \lesssim 2\times10^{-5}$ is excluded when neutrino masses are much smaller than the in-medium effective scale, with bounds depending on the solar neutrino solution (SMA-LMA-vacuum). The results demonstrate the importance of SN-medium effects for Majoron models and indicate that upcoming SN neutrino data could further constrain or uncover Majoron interactions at the $\mathcal{O}(10^{-5})$ level.

Abstract

Neutrino masses arising from the spontaneous violation of ungauged lepton-number are accompanied by a physical Goldstone boson, generically called Majoron. In the high-density supernova medium the effects of Majoron-emitting neutrino decays are important even if they are suppressed in vacuo by small neutrino masses and/or small off-diagonal couplings. We reconsider the influence of these decays on the neutrino signal of supernovae in the light of recent Super-Kamiokande data on solar and atmospheric neutrinos. We find that majoron-neutrino coupling constants in the range $3\times 10^{-7}\lsim g\lsim 2\times 10^{-5}$ or $g \gsim 3 \times 10^{-4}$ are excluded by the observation of SN1987A. Then we discuss the potential of Superkamiokande and the Sudbury Neutrino Observatory to detect majoron neutrino interactions in the case of a future galactic supernova. We find that these experiments could probe majoron neutrino interactions with improved sensitivity.

Figures (5)

• Figure 1: SN 1987A constraint on the majoron-neutrino effective coupling constants in the $g_{ee}-g_{eh}$ plane. Parameters corresponding to the SMA-MSW solution to the solar neutrino problem are assumed.
• Figure 2: SN 1987A constraint plotted in the $m_1-g_{11}$ plane. Parameters corresponding to the LMA-MSW solution to the solar neutrino problem are assumed, $\sin^22\theta=0.6$ and $\Delta_0=10^{-5}$ eV$^2$.
• Figure 3: Regions of total transition probability plotted in the $m_1-g_{11}$ plane. Here we assume the just--so solution to the solar neutrino problem, $\sin^22\theta=0.9$ and $\Delta_0=10^{-10}$ eV$^2$ and include both the effects of neutrino decays and oscillation.
• Figure 4: Signal expected in Super-Kamiokande due to the reaction $\bar{\nu}_e + p \to n+e^+$ for a galactic supernova. Here $N_\nu$ denotes the number of events for $g_{11}=0$ (solid line) and $g_{11}=10^{-4}$ (dashed line) with $g_{11}=g_{22}=g_{33}$.
• Figure 5: Signal expected at SNO due to the reaction $\nu_h + D \to \nu_h+p+n$ for a galactic supernova. Here $N_\nu$ denotes the number of events for the indicated values of $g_{11}$ with $g_{11}=g_{22}=g_{33}$.