Explosive nucleosynthesis with fast neutrino-flavor conversion in core-collapse supernovae

Abstract: Fast neutrino-flavor conversion (FFC) is a possible game-changing ingredient in core-collapse supernova (CCSN) theory. In this paper, we examine the impact of FFC on explosive nucleosynthesis by including the effects of FFC in conjunction with asymmetric neutrino emission into nucleosynthetic computations in a parametric way. We find that the ejecta compositions are not appreciably affected by FFC for elements lighter than Co, while the compositions are influenced by FFC for the heavier elements. We also find that the role of FFC varies depending on the asymmetric degree of neutrino emission ($m_{\rm asy}$) and the degree of neutrino-flavor mixing. The impact of FFC is not monotonic to $m_{\rm asy}$; The change in the ejecta composition increases for higher $m_{\rm asy}$ up to $\sim 10\%$ compared with that without FFC, whereas FFC has little effect on the nucleosynthesis in very large asymmetric neutrino emission ($\gtrsim 30 \%$). Our results suggest that FFC facilitates the production of neutron-rich ejecta in most cases, although it makes the ejecta more proton-rich if anti-neutrino conversion is more vigorous than that of neutrino. The key ingredient accounting for this trend is neutrino absorption, whose effects on nucleosynthesis can be quantified by simple diagnostics.