[论文解读] Self-induced spectral splits with multi-azimuthal-angle effects for different supernova neutrino fluxes

Alessandro Mirizzi|arXiv (Cornell University)|Aug 23, 2013

Neutrino Physics Research被引用 3

一句话总结

本文研究了超新星中微子味演化中的多方位角角（MAA）不稳定性，表明光谱交叉模式——尤其是单次交叉与多次交叉——决定了MAA效应是否会触发超出双模态或多重天顶角（MZA）不稳定性的新光谱分裂。在正质量顺序且u_e过量较强时，MAA引致的光谱交换类似于反质量顺序下的双模态效应；在中等味层次结构下，MZA延迟会抑制MAA增长，仅留下由双模态/MZA驱动的分裂。

ABSTRACT

It has been recently discovered that removing the axial symmetry in the multi-angle associated with the neutrino-neutrino interactions for supernova (SN) neutrinos, a new multi-azimuthal-angle (MAA) instability would trigger flavor conversions in addition to the ones caused by the bimodal and multi-zenith-angle (MZA) instabilities. We investigate the dependence of the MAA instability on the original SN neutrino fluxes, performing a stability analysis of the linearized neutrino equations of motion. We compare these results with the numerical evolution of the SN neutrino non-linear equations, looking at a local solution along a specific line of sight, under the assumption that the transverse variations of the global solution are small. We also assume that self-induced conversions are not suppressed by large matter effects. We show that the pattern of the spectral crossings (energies where F_{ u_e} = F_{ u_x}, and F_{\bar u_e} = F_{\bar u_x}) is crucial in determining the impact of MAA effects on the flavor evolution. For neutrino spectra with a strong excess of u_e over \bar u_e, presenting only a single-crossing, MAA instabilities would trigger new flavor conversions in normal mass hierarchy. In our simplified flavor evolution scheme, these would lead to spectral swaps and splits analogous to what produced in inverted hierarchy by the bimodal instability. Conversely, in the presence of spectra with a moderate flavor hierarchy, having multiple crossing energies, MZA effects would produce a sizable delay in the onset of the flavor conversions, inhibiting the growth of the MAA instability. In this case the splitting features for the oscillated spectra in both the mass hierarchies are the ones induced by the only bimodal and MZA effects.

研究动机与目标

• 理解多方位角角（MAA）不稳定性如何在已知的双模态和多重天顶角（MZA）效应之外影响超新星中微子味演化。
• 研究MAA不稳定性对初始中微子通量的依赖性，特别是光谱交叉结构（即F_u_e = F_u_x 与 F_u_e_bar = F_u_x_bar 的位置）。
• 将线性稳定性分析与在局部化、横向变化近似条件下的非线性数值演化进行比较。
• 评估在MAA区域内，自致味转换是否因介质效应而被抑制（假设其未被抑制）。

提出的方法

• 对中微子运动方程进行线性化稳定性分析，以识别MAA不稳定性增长速率。
• 将分析结果与沿特定视线的非线性方程数值演化结果进行比较，假设全局解中横向变化较小。
• 通过不同光谱交叉模式建模中微子通量：单次交叉（强u_e过量）与多次交叉（中等味层次结构）。
• 假设自致转换受介质效应的抑制可忽略不计，聚焦于真空类似动力学。
• 在不同质量顺序（正序与反序）下分析味演化结果，特别关注光谱交换与分裂。

实验结果

研究问题

• RQ1 初始中微子通量中光谱交叉的数量与位置如何影响MAA不稳定的启动与增长？
• RQ2 在何种条件下，MAA不稳定性会引致超出双模态与MZA不稳定性驱动的新型味转换？
• RQ3 具有多个交叉能量的中等味层次结构如何影响MAA驱动光谱分裂的时机与振幅？
• RQ4 在实际通量构型中，MZA效应在多大程度上延迟或抑制MAA不稳定性增长？

主要发现

• 对于具有强u_e过量且仅存在一次光谱交叉的中微子谱，在正质量顺序下，MAA不稳定性会触发新的味转换，导致光谱交换与分裂，其特征与反质量顺序下通过双模态不稳定性产生的结果相似。
• 对于具有中等味层次结构及多个交叉能量的谱，MZA效应会显著延迟味转换的启动，从而抑制MAA不稳定的增长。
• 当MAA增长因MZA延迟而被抑制时，两种质量顺序下的光谱特征完全由双模态与MZA效应主导，不再出现额外的MAA诱导分裂。
• 光谱交叉的模式是决定MAA效应是否会产生超出标准不稳定的可观测味演化特征的决定性因素。