Directional statistics for realistic weakly interacting massive particle direct detection experiments. II. 2D readout
Directional statistics for realistic weakly interacting massive particle direct detection experiments. II. 2D readout
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现实弱相互作用大粒子直接探测实验的方向统计。
DOI：
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发表时间：
2005
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通讯作者：
A. Green
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作者：
Ben Morgan;A. Green
Department of Physics and Astronomy，University of She Schweeld，Hicks Building，Houns field Road，She Schweeld，S3 7 RH，United Kingdom（Dated：February 5，2008）WIMP直接检测率的方向依赖性为区分WIMP信号和可能的背景提供了一个强大的工具。本文利用非参数循环统计方法研究了二维读出探测器从各向同性背景中分辨出WIMP信号所需的事件数。我们还检查了事件的数量需要i）检测偏离旋转对称，由于银河系晕的非对称性和ii）检测偏差的平均方向，由于潮汐流。如果测量反冲的感觉，那么20 -70个事件（取决于2-d读出的平面和探测器位置）将足以在90%的置信度下拒绝原始反冲角的各向同性。如果感官不能被测量，这些数字大约会增加两个数量级（相比之下，全三维读出的情况下会增加一个数量级）。减去太阳运动方向（随时间变化）后的角度分布更加各向异性，然而，如果对这些角度进行各向同性测试，那么所需的事件数量与3-d读出的情况相似。只有当银河系的晕被显著地减弱时，才能检测到旋转对称性的偏离。然而，由于潮汐流而引起的平均方向的偏差是可以检测到的，这取决于潮汐流的密度和方向。子午面（其中包含地球的自旋轴）是，对于所有的探测器位置，最佳的读出平面为拒绝各向同性。然而，在这个平面上的读出不能用于探测银河晕或方向垂直于银道面的流的衰减。在这些情况下，最佳读出平面取决于探测器的位置。
Department of Physics and Astronomy, University of Sheffield,Hicks Building, Hounsfield Road, Sheffield, S3 7RH, United Kingdom(Dated: February 5, 2008)The direction dependence of the WIMP direct detection rate provides a powerful tool for distin-guishing a WIMP signal from possible backgrounds. We study the the number of events requiredto discriminate a WIMP signal from an isotropic background for a detector with 2-d read-out usingnon-parametric circular statistics. We also examine the number of events needed to i) detect a devi-ation from rotational symmetry, due to flattening of the Milky Way halo and ii) detect a deviationin the mean direction due to a tidal stream. If the senses of the recoils are measured then of order20-70 events (depending on the plane of the 2-d read out and the detector location) will be sufficientto reject isotropy of the raw recoil angles at 90% confidence. If the senses can not be measuredthese number increase by roughly two orders of magnitude (compared with an increase of one orderof magnitude for the case of full 3-d read-out). The distributions of the reduced angles, with the(time dependent) direction of solar motion subtracted, are far more anisotropic, however, and if theisotropy tests are applied to these angles then the numbers of events required are similar to the caseof 3-d read-out. A deviation from rotational symmetry will only be detectable if the Milky Way halois significantly flattened. The deviation in the mean direction due to a tidal stream is potentiallydetectable, however, depending on the density and direction of the stream. The meridian plane(which contains the Earth’s spin axis) is, for all detector locations, the optimum read-out plane forrejecting isotropy. However read-out in this plane can not be used for detecting flattening of theMilky Way halo or a stream with direction perpendicular to the galactic plane. In these cases theoptimum read-out plane depends on the detector location.