Statistics of Daily Modulation in Dark Matter Direct Detection Experiments
The Pennsylvania State University（宾夕法尼亚州立大学）；Princeton University（普林斯顿大学）；University of Wisconsin-Madison（威斯康星大学麦迪逊分校）；University of Toronto（多伦多大学）；University of Oregon（俄勒冈大学）
Carlos Blanco, Joshua W. Foster, Yonatan Kahn, Benjamin Lillard
The time-dependent modulation of the event rate in dark matter direct detection experiments, arising from the motion of the Earth with respect to the Galactic rest frame, is a distinctive signature whose observation is crucial for claiming a discovery of dark matter. While annual modulation has been well studied for decades, daily modulation due to the Earth's rotation has attracted increased attention recently due to the identification of anisotropic solid-state detector materials that yield a direction-dependent scattering rate without sacrificing the overall rate. We perform a statistical analysis of daily modulation in dark matter scattering experiments, with the goal of maximizing the statistical significance of a modulating signal in the presence of an unknown background rate, which may be either flat (non-modulating), or modulating over a 24-hour period with a known or unknown phase. In the background-dominated regime, we find that the discovery significance scales as $f_\text{RMS} \sqrt{T}$, where $T$ is the total exposure time and $f_\text{RMS}$ is the root-mean-square modulation amplitude; in particular, the significance continues to improve with exposure rather than saturating due to systematic uncertainties in the background rate. Using anisotropic trans-stilbene detectors for sub-GeV dark matter as a benchmark example, we provide prescriptions for optimizing the significance for a given total detector mass and location. In an example analysis using three detectors, optimizing the detector orientations can reduce the required exposure by a factor of $\sim 5$ for a desired discovery or exclusion significance, even after profiling over an unknown modulating background phase.
SENSEI: A Search for Diurnal Modulation in sub-GeV Dark Matter Scattering
University of California, Berkeley（加州大学伯克利分校）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）；Fermi National Accelerator Laboratory（费米国家加速器实验室）；Kavli Institute for Cosmological Physics, University of Chicago（芝加哥大学卡弗里宇宙物理学研究所）；Institut für Hochenergiephysik der Österreichischen Akademie der Wissenschaften（奥地利科学院高能物理研究所）；Technische Universität Wien（维也纳工业大学）；Universidad Nacional Autónoma de México（墨西哥国立自治大学）；Tel-Aviv University（特拉维夫大学）；University of Oregon（俄勒冈大学）；Stony Brook University（石溪大学）
Dark Matter Weather: Probing Sub-GeV Interactions with Earth-Shielding Modulation
University of Liverpool（利物浦大学）；SLAC National Accelerator Laboratory, Stanford University（斯坦福大学 SLAC 国家加速器实验室）；Kavli Institute for Particle Astrophysics and Cosmology, Stanford University（斯坦福大学卡弗里粒子天体物理与宇宙学研究所）
