Instituto de Física Corpuscular (IFIC), CSIC-Universitat de València, Apartado de Correos 22085, E-46071 Valencia, Spain.
Phys Rev Lett. 2014 Aug 29;113(9):091103. doi: 10.1103/PhysRevLett.113.091103. Epub 2014 Aug 28.
The IceCube experiment has recently reported the observation of 28 high-energy (>30 TeV) neutrino events, separated into 21 showers and 7 muon tracks, consistent with an extraterrestrial origin. In this Letter, we compute the compatibility of such an observation with possible combinations of neutrino flavors with relative proportion (αe:αμ∶ατ)⊕. Although the 7∶21 track-to-shower ratio is naively favored for the canonical (1∶1∶1)⊕ at Earth, this is not true once the atmospheric muon and neutrino backgrounds are properly accounted for. We find that, for an astrophysical neutrino E(-2) energy spectrum, (1∶1∶1)⊕ at Earth is disfavored at 81% C.L. If this proportion does not change, 6 more years of data would be needed to exclude (1∶1∶1)⊕ at Earth at 3σ C.L. Indeed, with the recently released 3-yr data, that flavor composition is excluded at 92% C.L. The best fit is obtained for (1∶0∶0)⊕ at Earth, which cannot be achieved from any flavor ratio at sources with averaged oscillations during propagation. If confirmed, this result would suggest either a misunderstanding of the expected background events or a misidentification of tracks as showers, or even more compellingly, some exotic physics which deviates from the standard scenario.
冰立方实验最近报告了 28 个高能（>30 TeV）中微子事件的观测结果，这些事件分为 21 个簇射和 7 个μ子迹，与外星起源一致。在这封信中，我们计算了这种观测结果与可能的中微子味组合（αe：αμ∶ατ）⊕的兼容性。尽管在地球表面，7∶21 的μ子迹-簇射比对于规范（1∶1∶1）⊕是有利的，但一旦正确考虑了大气μ子和中微子背景，情况就不是这样了。我们发现，对于天体物理中微子 E(-2)能谱，（1∶1∶1）⊕在地球表面的置信度为 81%。如果这个比例不变，那么还需要 6 年的数据才能在 3σ C.L.排除（1∶1∶1）⊕在地球表面的情况。事实上，最近发布的 3 年数据已经以 92%的置信度排除了这种味道组成。在地球表面，最好的拟合是（1∶0∶0）⊕，这在传播过程中平均振荡的任何源的任何味道比都无法实现。如果得到证实，这一结果要么表明对预期背景事件的理解有误，要么表明对μ子迹的识别有误，或者更有说服力的是，存在一些偏离标准场景的奇特物理现象。
