Muon-induced collisional flavor instability in core-collapse supernova

Neutrinos are known to undergo flavor conversion among their three flavors. In the theoretical modeling of core-collapse supernova, there has been a great deal of attention to recent discoveries of a new type of neutrino flavor conversions, namely collisional flavor instability (CFI), in which the instability is induced by the flavor-dependent decoherence due to the disparity of neutrino-matter interactions among flavors. In this paper, we study how the appearance of on-shell muons and associated neutrino-matter interactions can impact CFIs based on linear stability analysis of flavor conversions. Some striking results emerge from the present study. First, we analytically show that breaking beta and pair equilibrium is a necessary condition to trigger CFIs. This also indicates that CFIs with on-shell muons could appear in eτ and μτ neutrino mixing sectors in very high-density region (≳1013 g/cm3), exhibiting a possibility of large impacts of CFIs on core-collapse supernova. Second, resonancelike CFIs, having a much higher growth rate than normal CFIs, can be triggered by muons. The resonance point of CFIs is different between eτ and μτ sectors; the former (latter) occurs at μe(μ)=μn-μp, where μi denotes the chemical potential of i constitute (n and p represent neutrons and protons, respectively). Our result suggests that the nonlinear evolution of CFI with on-shell muons would induce flavor conversions with the complex interplay among all three different neutrino-mixing sectors.