Probing light dark matter and core-collapse supernova phenomena with neutrinos at SNO+

休伊特将研究SNO+对银河晕中宇宙射线电子和质子向上散射的光（次gev）暗物质的敏感性，这一想法是由Cappiello和Beacom最近的一篇论文（PRD 100(2019) 10,103011）提出的。这些粒子由于其低动量而倾向于逃避暗物质直接探测实验，但它们可能在SNO+中留下高达O(10) MeV的可见能量。SNO+异常低的背景可能会提高这一相对未被探索的暗物质候选者范围的限制（由卡皮罗和比科姆根据其他实验数据计算）。该项目的这一部分包括银河晕、宇宙射线的不同模型，以及奇异粒子在地壳2公里处传播的简化模拟，随后是基于geant4的探测器对单个事件的完整模拟。休伊特项目第二部分的主要焦点将转移到一颗（有希望但罕见的）星系核心坍缩超新星的中微子上。他将通过改进探测器对同步事件（表明反β衰变）和爆发模式（结合不同的带电和中性电流过程）的近乎实时的分析，寻求提高SNO+对前超新星中微子和超新星爆发的灵敏度。他还将研究在主闪烁体体积之外增加SNO+对中微子事件的接受度的策略，这项任务将涉及复杂光学探测器区域的详细模拟和新重建技术的开发。作为这项研究的一部分，他将研究是否有可能从这些主要基于水的事件中提取方向信息，因为这些事件可能有助于确定超新星的方向-通过全球超新星中微子预警系统（SNEWS）网络尽快向天文观测者群体传递重要信息。休伊特还将研究一系列暗物质模型对观测到的超新星中微子的时间和能谱以及探测器中其他相关能量沉积的影响。了解这些效应将进一步为SNO+和其他中微子实验提供在银河系超新星事件中可能观测到的不同现象的范围，并提高SNEWS为后续实时观测提供及时、可靠、相关信息的能力，以及与电磁和引力“信使”的相关性。

Mr Hewitt will investigate the sensitivity of SNO+ to light (sub-GeV) dark matter up-scattered by cosmic ray electrons and protons in the galactic halo, an idea prompted by a recent paper by Cappiello and Beacom (PRD 100 (2019) 10, 103011). These particles tend to evade dark matter direct detection experiments because of their low momentum, but they may leave up to O(10) MeV visible energy in SNO+. SNO+'s exceptionally low backgrounds could improve limits (calculated by Cappiello and Beacom based on other experimental data) for this relatively unexplored range of dark matter candidates. This part of the project involves different models of the galactic halo, cosmic rays, and simplified simulation of the propagation of exotic particles through 2km of the Earth's crust, followed by full Geant4-based detector simulation of individual events.The main focus of the second part of Mr Hewitt's project will shift to neutrinos from a (prospective but rare) galactic core-collapse supernova. He will seek to improve SNO+ sensitivity to pre-supernova neutrinos and the supernova burst by improving the detector's nearly real-time analysis of coincident events (indicative of inverse beta decay) and burst patterns (incorporating different charged and neutral-current processes). He will also investigate strategies for increasing SNO+ acceptance of neutrino events outside the main scintillator volume, a task which will involve detailed simulation and the development of novel reconstruction techniques in areas of the detector with complicated optics. As part of this investigation, he will examine whether it is possible to extract directional information from at least some of these largely water-based events, since such events may help localize the direction of the supernova - important information to relay as quickly as possible to the astronomical observer community via the global Supernova Neutrino Early Warning System (SNEWS) network. Mr Hewitt will also investigate the impact of a range of dark matter models on the observed time and energy spectra of the supernova neutrinos and other associated energy depositions in the detector. Understanding these effects will further inform SNO+ and other neutrino experiments as to the range of different phenomena which may be observed in the event of a galactic supernova, and improve the ability of SNEWS to produce timely, reliable, relevant information for subsequent real-time observations, as well as correlation with both electromagnetic and gravitational "messengers".