中微子味转换对中微子主导吸积流产生的弥散中微子背景的影响
Impact of Neutrino Flavour Conversion on the Diffuse Neutrino Background from Neutrino-dominated Accretion Flows
中文总结 AI 辅助
该研究基于核心坍缩超新星回落吸积模拟，探究中微子主导吸积流的中微子辐射特性，评估中微子味转换对弥散中微子背景的影响，发现其信号强度依赖中微子质量顺序，正质量顺序下或可被下一代探测器探测到。
中文摘要 AI 辅助
中微子主导吸积流（NDAFs）被认为形成于某些核心坍缩超新星（CCSNe）的回落吸积阶段，这类系统会产生大量中微子辐射，其在宇宙历史中的累积贡献形成了弥散NDAF中微子背景（DNNB）。当中微子从源传播到地球时，味转换会显著改变观测到的中微子能谱，进而影响DNNB的可探测性。本研究基于回落式CCSNe模拟，探究前身星质量、金属丰度和初始爆炸能量对NDAFs中微子辐射的影响；计算NDAFs产生的重轻子中微子（$\nu_x$）能谱并将其纳入DNNB预测，发现未发生振荡的$\nu_x$能谱比电子反中微子（$\bar{\nu}_e$）低一个数量级以上。利用江门中微子实验（JUNO）报告的最新中微子振荡参数，评估味转换对DNNB的影响，推导正质量顺序和 inverted质量顺序对应的能谱；进一步估算JUNO和Hyper-Kamiokande的预期事例数，发现预测的DNNB信号强烈依赖中微子质量顺序：正质量顺序下下一代中微子探测器可能探测到DNNB， inverted质量顺序下信号被显著抑制，探测难度大幅提升。
英文摘要
Neutrino-dominated accretion flows (NDAFs) are believed to form during the fallback accretion phase of some core-collapse supernovae (CCSNe). Such systems produce copious neutrino emission, whose cumulative contribution over cosmic history forms the diffuse NDAF neutrino background (DNNB). As neutrinos propagate from the source to Earth, flavour conversion can significantly modify the observed neutrino spectra and consequently the detectability of the DNNB. In this work, based on fallback CCSN simulations, we investigate the effects of progenitor mass, metallicity, and initial explosion energy on neutrino emission from NDAFs. We calculate the heavy-lepton neutrino ($ν_x$) spectra from NDAFs and incorporate them into DNNB predictions. We find that the unoscillated $ν_x$ spectra are more than an order of magnitude lower than those of electron antineutrinos $\barν_e$. Using the latest neutrino oscillation parameters reported by the Jiangmen Underground Neutrino Observatory (JUNO), we evaluate the impact of flavour conversion on the DNNB and derive the corresponding spectra for both the normal and inverted mass orderings. We further estimate the expected event numbers in JUNO and Hyper-Kamiokande. We find that the predicted DNNB signal is strongly dependent on the neutrino mass ordering. While the DNNB may be detectable in the normal ordering with next-generation neutrino detectors, the signal is significantly suppressed in the inverted ordering, making detection considerably more challenging.
