Matter-enhanced antineutrino flavor transformation and supernova nucleosynthesis

Matter-enhanced antineutrino flavor transformation between $\bar\nu_e$ and $\bar\nu_{\mu(\tau)}$ can occur in supernovae if the vacuum masses for these species satisfy $m_{\bar\nu_e}>m_{\bar\nu_{\mu(\tau)}}$. For $\delta m^2> 1$ eV$^2$, such flavor transformation can affect the electron fraction $Y_e$ in the neutrino-heated supernova ejecta. We point out that such flavor transformation will not drive $Y_e>0.5$ at the $r$-process nucleosynthesis epoch in the best available supernova model for such nucleosynthesis. Consequently, there is no obvious conflict between matter-enhanced antineutrino flavor transformation $\bar\nu_e\rightleftharpoons\bar\nu_{\mu(\tau)}$ and $r$-process nucleosynthesis in the neutrino-heated supernova ejecta.