arXiv 1702.083382017-02hep-phastro-ph.SRhep-ex

集体中微子振荡与中微子波包

Collective neutrino oscillations and neutrino wave packets

Evgeny Akhmedov, Joachim Kopp, Manfred Lindner

备注：: LaTeX, 38 pages. V2: typo in eq. (9) corrected; small changes in the text. Matches the published version

摘要：

研究了波包分离引起的退相干对稠密中微子气体中集体中微子振荡的影响。我们估计了核塌缩超新星中中微子的波包长度和中微子相干长度，然后在中微子味跃迁的密度矩阵形式下考虑了退相干效应.首先，我们证明了真空中中微子振荡的退相干效应是由一个阻尼项描述的密度矩阵的运动方程的中微子作为一个整体（相对于中微子密度矩阵的固定动量分量）。接下来，我们考虑中微子振荡在普通物质和稠密中微子背景下，在绝热和非绝热制度。在后一种情况下，我们研究了两个具体的模型绝热违反-一个短期和另一个扩展的非绝热。结果表明，在绝热情况下，中微子密度矩阵的运动方程中存在阻尼项（与真空振荡情况相同），而在非绝热情况下，一般不存在阻尼项.

英文摘要：

Effects of decoherence by wave packet separation on collective neutrino oscillations in dense neutrino gases are considered. We estimate the length of the wave packets of neutrinos produced in core collapse supernovae and the expected neutrino coherence length, and then proceed to consider the decoherence effects within the density matrix formalism of neutrino flavour transitions. First, we demonstrate that for neutrino oscillations in vacuum the decoherence effects are described by a damping term in the equation of motion of the density matrix of a neutrino as a whole (as contrasted to that of the fixed-momentum components of the neutrino density matrix). Next, we consider neutrino oscillations in ordinary matter and dense neutrino backgrounds, both in the adiabatic and non-adiabatic regimes. In the latter case we study two specific models of adiabaticity violation -- one with short-term and another with extended non-adiabaticity. It is demonstrated that, while in the adiabatic case a damping term is present in the equation of motion of the neutrino density matrix (just like in the vacuum oscillation case), no such term in general appears in the non-adiabatic regime.

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