Equipment and Infrastructure support for the PICO/PICASSO Dark Matter Search Project

寻找宇宙中神秘失踪的质量已经成为当今粒子物理学和宇宙学面临的巨大挑战之一。天文观测表明，宇宙中只有1%的物质是发光的，现在有令人信服的证据表明，宇宙中85%的引力可追溯物质是一种新的外来物质，不同于我们周围含有质子、中子和电子的“普通”物质。这种所谓的冷暗物质（CDM）被认为是由所谓的wimp（弱相互作用大质量粒子）组成的，这是一种中性粒子，大约比质子重10到1000倍，它们彼此之间以及与普通物质之间的相互作用极其微弱。毕加索*暗物质实验转向了寻找弱相互作用大质量粒子。它基于液体到蒸汽的相变，这种相变可以由WIMP与亚稳态过热液滴中的原子核相互作用引起。毕加索发现的过热液体技术强大的背景辨别特性保证了“背景盲”操作长达吨年的曝光。因此，在2012年12月，两个在暗物质搜索领域领先的小组，毕加索和COUPP在新的PICO合作中联合起来，共同致力于在SNOLAB进行500公斤的暗物质实验。在250L的气泡室中，以过热的C4F10或C3F8作为活动目标，该实验符合下一代暗物质实验（G2）的定义，在自旋依赖相互作用和轻WIMP质量领域，没有其他G2实验具有类似的灵敏度。加拿大毕卡索/ PICO特遣队由五个机构的研究小组组成：阿尔伯塔大学、劳伦森大学、蒙特里萨大学、皇后大学和多伦多大学。在这项拨款申请中，我们要求为完成一系列研发项目提供基础设施和设备支持，这些项目是500公斤探测器筹备阶段的一部分。加拿大的超对称天体研究项目

The quest for the mysterious missing mass of the Universe has become one of the big challenges for today's particle physics and cosmology. Astronomical observations show that only 1% of the matter of the Universe is luminous and there is now convincing evidence that 85% of all gravitationally traceable matter in the Universe is of a new exotic kind, different from the "ordinary" matter surrounding us with its protons, neutrons and electrons. This so-called Cold Dark Matter (CDM) is thought to consist of so-called WIMPs (Weakly Interacting Massive Particles), neutral particles, about ten to thousand times heavier than a proton and which interact extremely weakly with each other and ordinary matter. The PICASSO* dark matter experiment is tuned to the search for WIMPs. It is based on liquid-to-vapour phase transitions which can be induced by WIMP interactions with nuclei in metastable superheated droplets. The powerful background discrimination features of the superheated liquid technique discovered by PICASSO promise “background blind” operation for up to tonne - year exposures. Therefore in December 2012 the two leading groups in the field of dark matter searches with superheated liquids, PICASSO and COUPP joint forces within the new PICO collaboration to work together towards a 500 kg dark matter experiment at SNOLAB. With superheated C4F10 or C3F8 as the active target in a 250L bubble chamber this experiment meets the definition of a next generation dark matter experiment (G2) and no other G2 experiment would have comparable sensitivities in the sectors of spin-dependent interactions and light WIMP masses. The Canadian PICASSO / PICO contingent consists of research groups of five institutions: University of Alberta, Laurentian University, Université de Montréal, Queen’s University and University of Toronto. In this grant request we ask for infrastructure and equipment support for the completion of a serious of R&D projects which are part of the preparatory phase of the 500 kg detector. *Project In Canada to Search for Supersymmetric Objects Projet d'Identification de CAnditats Supersymetriques Sombres