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Searches for small-scale anisotropies from neutrino point sources with three years of IceCube data

机译:使用三年的IceCube数据从中微子点源中搜索小范围的各向异性

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Recently, IceCube found evidence for a diffuse signal of astrophysical neutrinos in an energy range of similar to 60 TeV to the PeV-scale [1]. The origin of those events, being a key to understanding the origin of cosmic rays, is still an unsolved question. So far, analyses have not succeeded to resolve the diffuse signal into point-like sources. Searches including a maximum-likelihood-ratio test, based on the reconstructed directions and energies of the detected down- and up-going neutrino candidates, were also performed on IceCube data leading to the exclusion of bright point sources. In this paper, we present two methods to search for faint neutrino point sources in three years of IceCube data, taken between 2008 and 2011. The first method is an autocorrelation test, applied separately to the northern and southern sky. The second method is a multipole analysis, which expands the measured data in the northern hemisphere into spherical harmonics and uses the resulting expansion coefficients to separate signal from background. With both methods, the results are consistent with the background expectation with a slightly more sparse spatial distribution, corresponding to an underfluctuation. Depending on the assumed number of sources, the resulting upper limit on the flux per source in the northern hemisphere for an E-2 energy spectrum ranges from similar to 1.5. 10(-8) GeV/cm(2) s(-1), in the case of one assumed source, to similar to 4. 10(-10) GeV/cm(2) s(-1), in the case of 3500 assumed sources. (C) 2015 Elsevier B.V. All rights reserved.
机译:最近,IceCube发现证据表明,天文学中微子的扩散信号的能量范围与PeV尺度相近60 TeV [1]。这些事件的起源是理解宇宙射线起源的关键,但仍未解决。到目前为止,分析还没有成功地将漫射信号解析为点状源。还基于IceCube数据对搜索到的向下和向上的中微子候选者的重构方向和能量进行了包括最大似然比测试在内的搜索,从而排除了亮点源。在本文中,我们提出了两种方法,用于在2008年至2011年之间的三年IceCube数据中搜索微弱的中微子点源。第一种方法是自相关测试,分别应用于北部和南部的天空。第二种方法是多极分析,该方法将北半球的测量数据扩展为球形谐波,并使用所得扩展系数将信号与背景分离。两种方法的结果都与背景预期一致,空间分布略微稀疏,这对应于波动不足。取决于假设的源数,对于E-2能谱,北半球每个源的通量的最终上限约为1.5。在假设一种来源的情况下,其10(-8)GeV / cm(2)s(-1)类似于4。在这种情况下,其10(-10)GeV / cm(2)s(-1) 3500个假定来源。 (C)2015 Elsevier B.V.保留所有权利。

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