Division of Science, NAOJ

2025.4.30 highlights

Exploring Sterile Neutrinos with Core-collapse Supernova Simulations

In the Standard Model of particle physics, which is the most fundamental framework for describing our Universe, there are three flavors of neutrinos: electron-type, muon-type, and tauon-type. Then, what would happen if a fourth type of neutrinos, which is called sterile neutrinos, that we have never seen before existed? On the other hand, it has been reported that the number of antineutrinos emitted from nuclear reactors is slightly smaller than theoretically predicted. Since sterile neutrinos can explain this anomaly if they exist, they are attracting attention in recent years. If sterile neutrinos exist, they could also appear in collapsing stars through the neutrino oscillations. Thus, it could be possible to detect their signature through astronomical

supernova observations.

Following this context, Kanji Mori (JSPS Research Fellow), Prof. Tomoya Takiwaki, Prof. Kazunori Kohri, and Prof. Hiroki Nagakura (NAOJ Fellow) at National Astronomical Observatory of Japan investigated the effect of sterile neutrinos on supernova explosions by performing two-dimensional simulations for supernovae that take into account the oscillation between electron neutrinos and sterile neutrinos. As a result, they found that when the mixing angle between sterile neutrinos and electron neutrinos is sufficiently large, the flux of electron neutrinos decreases, and supernova explosions fail. However, supernovae have exploded in reality and thus these models contradict observations. Therefore, it is possible to constrain the properties of sterile neutrinos based on the supernova explodability, although systematic uncertainties remain. In the future, they would like to obtain more accurate constraints by systematically investigating the dependence on the simulation setup.

The results of this research were published in Physical Review D.

Figure 1. The parameter space for sterile neutrinos (Fig. 1 in Mori et al. 2025). The points A-E show the parameters adopted in the simulations. The green region is the parameters preferred by the reactor antineutrino anomaly, and the red region is the parameters preferred by particle experiments. The orange line is the boundary of the explodability suggested by this study, and a supernova will explode only below the line.

【Publication Information】
Journal: Physical Review D Title: “Core-collapse supernova explosions hindered by eV-mass sterile neutrinos” Authors: Kanji Mori, Tomoya Takiwaki, Kazunori Kohri, Hiroki Nagakura URL: https://journals.aps.org/prd/abstract/10.1103/PhysRevD.111.083046