IceCube HESE 12-year data release

This data release describes a revisited analysis of the IceCube high-energy starting events (HESE) sample with an additional 4.5 years of data that employs a full-resimulation reconstruction approach, DirectFit, which exactly incorporates recent updates in glacial ice modeling. These updates include a microscopic description of the observed ice anisotropy due to birefringence and a full description of ice layer undulations in three dimensions. Each event is reconstructed with the Approximate Bayesian Computation method, with the posterior sample points then fitted to an asymmetric directional probability density function. For further details, refer to the IceCube publication PoS-ICRC23-1030 / arXiv:2307.13878 Note on interpretation Reconstructed quantities for subsets of these events have been published previously. IceCube utilizes several event reconstructions, each with different strengths and employed in different contexts. DirectFit, the reconstruction in this data release, performs accurate event reconstruction, but is too computationally expensive to run on large scale Monte Carlo (MC). Therefore this data release should not be employed in a forward-folding likelihood fit for MC-based spectral analyses. Instead, as the reconstruction utilizes a complete description of the ice, the dataset is meant to provide accurate directional constraints for HESE events and for use in neutrino source searches. We highlight the differences between the reconstructions listed here, and those available elsewhere for subsets of this sample, below. For overlapping events already present in the previous 7.5 year dataset (arxiv:2011.03545), the reconstructions provided here may be compared to those in Appendix J. The reconstructions in Appendix J were obtained with DirectFit, but using an older ice model. Differences primarily arise from the updates to ice optical modeling and/or changes in the reconstruction routine (shower vs track) applied for select events. As the new ice model leads to a generally improved data-MC agreement in both calibration and physics data, the resulting fits are as a result preferred. The per-event differences between the fits may allow to conservatively gauge the impact of systematic detector uncertainties. For overlapping events already present in the previous 7.5 year dataset (arxiv:2011.03545), the reconstructions provided here utilize a different algorithm from those in Appendix F and listed as part of that data release. Specifically, the energies and directions published here should not be combined with the spectral fitting tools accompanying the 7.5 year dataset. Diffuse spectral analysis rely on likelihood-based reconstructions (arXiv:1311.4767) that leverage tabulated light yield approximations. Such algorithms are substantially more computationally efficient than DirectFit and are fast enough to be applied to large scale Monte Carlo, as required for forward-folding fits, at a cost of reduced accuracy. For overlapping events already present in the IceCat-1 catalog of alert tracks and released in real time via GCN/AMON, the visible energy reported here should not be compared to arxiv:2304.01174 (Tab. 3) and published in the accompanying data release . The IceCat-1 data release reports the most likely neutrino energy assuming a power-law spectral index of -2.19 at a given declination. The energies reported here correspond to the visible energy detected by IceCube. Note on event times The Modified Julian Date (MJD) is provided here for each event. In previously published HESE datasets that include the MJD, events that occurred between 2012-06-30 and 2015-05-17 were one second behind UTC time due to a master clock firmware issue. This offset has been corrected for in this data release; the overlapping events that fall within those dates will have a one second difference when compared to previous data releases. For those cases the MJDs provided here should be preferred. Data release Provided in this release is data.npy, which is a numpy structured array that contains the 164 reconstructed events that pass the HESE selection. The structured array contains the following fields: ('id', '< i4') ('mjd', '< f8') ('ra', '< f4') ('dec', '< f4') ('params', [('f0', '< f8'), ('f1', '< f8'), ('f2', '< f8'), ('f3', '< f8'), ('f4', '< f8'), ('f5', '< f8'), ('f6', '< f8'), ('f7', '< f8')]) ('reconstruction', 'S10') ('energy', '< f4') ('drlogl', '< f4') For each event, id corresponds to the event-ID consistent with prior HESE data releases, mjd is the Modified Julian Date when the event was observed, ra and dec correspond to the most-probable arrival direction, params corresponds to the eight parameters that describe the directional probability density function (PDF) using a generalized Fisher-Bingham distribution, reconstruction corresponds to the algorithm used by DirectFit, and energy the most-probable visible energy. For more details on the directional PDF construction see this paper....本数据集发布针对冰立方（IceCube）高能起始事件（High-Energy Starting Events, HESE）样本的重新分析工作，新增了4.5年的观测数据，并采用了全再模拟重建方法DirectFit，该方法完整纳入了冰川冰模型的最新更新内容。 这些更新包括对由双折射引起的观测冰各向异性的微观描述，以及对三维冰层起伏的完整刻画。 本数据集中的每个事件均通过近似贝叶斯计算（Approximate Bayesian Computation, ABC）方法完成重建，随后将后验样本点拟合为非对称方向概率密度函数。 如需进一步了解细节，请参阅冰立方合作组发表的论文PoS-ICRC23-1030 / arXiv:2307.13878。 关于事件解释的说明：本样本部分事件的重建量此前已发表。冰立方采用了多种事件重建算法，各有其适用场景与优势。本数据集发布采用的DirectFit重建方法可实现高精度的事件重建，但计算成本过高，无法在大规模蒙特卡洛（Monte Carlo, MC）模拟中运行。因此，本数据集不适用于基于MC的谱分析中的前向折叠似然拟合。 鉴于该重建方法完整刻画了冰介质的光学特性，本数据集旨在为HESE事件提供精确的方向约束，并可用于中微子源搜寻工作。 下文将详述本数据集提供的重建方法与该样本其他公开重建方法之间的差异。 对于此前7.5年数据集（arXiv:2011.03545）中已收录的重叠事件，可将本数据集提供的重建结果与该数据集附录J中的结果进行对比。附录J中的重建结果同样采用DirectFit方法，但使用了旧版冰模型。二者的差异主要源于冰光学建模的更新，以及针对特定事件采用的重建流程（簇射 vs 径迹）的调整。 由于新版冰模型在校准数据与物理数据中均显著改善了数据与MC模拟的匹配度，因此本数据集得到的拟合结果更优。事件间的拟合差异可用于保守评估探测器系统不确定度的影响。 对于此前7.5年数据集（arXiv:2011.03545）中已收录的重叠事件，本数据集提供的重建方法与该数据集附录F中收录的重建算法存在差异。具体而言，本文发布的能量与方向信息不应与该7.5年数据集配套的谱拟合工具结合使用。 弥散谱分析通常依赖于基于似然的重建方法（arXiv:1311.4767），该方法利用制表的光产额近似。此类算法的计算效率远高于DirectFit，可快速应用于大规模MC模拟以满足前向折叠拟合的需求，但代价是重建精度有所降低。 对于已收录于IceCat-1预警径迹星表并通过GCN/AMON实时发布的重叠事件，本数据集报告的可见能量不应与arXiv:2304.01174（表3）及其配套数据发布中的结果进行对比。IceCat-1数据集报告的是假设能谱指数为-2.19的幂律谱下，给定赤纬对应的最可几中微子能量；而本数据集报告的能量为冰立方探测到的可见能量。 关于事件时间的说明：本数据集为每个事件提供了修正儒略日（Modified Julian Date, MJD）。在此前已包含MJD的HESE数据集出版版本中，2012年6月30日至2015年5月17日期间发生的事件因主时钟固件问题，其记录时间比协调世界时（Coordinated Universal Time, UTC）慢1秒。本数据集已修正该时间偏移；与此前数据集相比，处于该时间段内的重叠事件的MJD存在1秒的差异，因此应优先采用本数据集提供的MJD值。 数据集内容：本发布包含data.npy文件，该文件为numpy结构化数组，包含164个通过HESE筛选标准的重建事件。该结构化数组包含以下字段：('id', '<i4')、('mjd', '<f8')、('ra', '<f4')、('dec', '<f4')、('params', [('f0', '<f8'), ('f1', '<f8'), ('f2', '<f8'), ('f3', '<f8'), ('f4', '<f8'), ('f5', '<f8'), ('f6', '<f8'), ('f7', '<f8')])、('reconstruction', 'S10')、('energy', '<f4')、('drlogl', '<f4')。 对于每个事件，id为与此前HESE数据集一致的事件编号；mjd为事件观测的修正儒略日；ra与dec为最可几的到达方向；params为描述广义费舍尔-宾厄姆分布（generalized Fisher-Bingham distribution）下方向概率密度函数的8个参数；reconstruction为DirectFit算法的标识；energy为最可几的可见能量。如需了解方向概率密度函数构建的更多细节，请参阅该论文。