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arXiv 0707.1998hep-phastro-ph
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超新星集体中微子味跃迁和轨迹平均的作用

Collective neutrino flavor transitions in supernovae and the role of trajectory averaging

G. L. Fogli, E. Lisi, A. Marrone, A. Mirizzi

备注：
v2 (27 pages, including 9 eps figures). Typos removed, references updated. Minor comments added. Corrected numerical errors in Eq.(6). Matches the published version
发表信息：
JCAP 0712:010,2007
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摘要：

超新星中微子振荡的非线性效应，与中微子自相互作用，是已知的，以诱导集体风味转变附近的超新星核心θ_13 \neq 0。在非常浅的电子密度分布的情况下，这些转换已被证明与普通物质的影响，共同产生正常和倒置层次的光谱失真耦合。在这项工作中，我们考虑了一个互补的情况下，其特征在于较高的电子密度，所示的反弹后冲击波模拟。在这种情况下，早期的集体味道转变与后来的普通物质效应脱钩。此外，这样的过渡变得更适合于数值计算和分析的解释，而在正常的层次，他们基本上消失。数值计算了与自相互作用效应有关的区域内的中微子密度矩阵。在中微子轨道之间的平均交叉角的近似下，我们的模拟整齐地显示了最近在文献中讨论的同步，双极振荡和光谱分裂的集体现象。在非平均中微子轨迹的更现实（但计算要求）的情况下，我们的模拟没有显示新的重要特征，除了双极章动等“精细结构”的涂抹。我们的结果似乎表明，至少对于非浅物质密度分布，平均中微子轨迹在最终结果中起着次要作用。在这种情况下，nu_e和nu_{μ,τ}光谱在临界能量以上的交换可能代表了倒置层次的明确标志，特别是对于足够小以使进一步的物质效应无关的theta_{13}。

英文摘要：

Non-linear effects on supernova neutrino oscillations, associated with neutrino self-interactions, are known to induce collective flavor transitions near the supernova core for theta_13 \neq 0. In scenarios with very shallow electron density profiles, these transformations have been shown to couple with ordinary matter effects, jointly producing spectral distortions both in normal and inverted hierarchy. In this work we consider a complementary scenario, characterized by higher electron density, as indicated by post-bounce shock-wave simulations. In this case, early collective flavor transitions are decoupled from later, ordinary matter effects. Moreover, such transitions become more amenable to both numerical computations and analytical interpretations in inverted hierarchy, while they basically vanish in normal hierarchy. We numerically evolve the neutrino density matrix in the region relevant for self-interaction effects. In the approximation of averaged intersection angle between neutrino trajectories, our simulations neatly show the collective phenomena of synchronization, bipolar oscillations, and spectral split, recently discussed in the literature. In the more realistic (but computationally demanding) case of non-averaged neutrino trajectories, our simulations do not show new significant features, apart from the smearing of ``fine structures'' such as bipolar nutations. Our results seem to suggest that, at least for non-shallow matter density profiles, averaging over neutrino trajectories plays a minor role in the final outcome. In this case, the swap of nu_e and nu_{μ,τ} spectra above a critical energy may represent an unmistakable signature of the inverted hierarchy, especially for theta_{13} small enough to render further matter effects irrelevant.

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