COUPP-250 kg. A Large-Mass Bubble Chamber Search for Weakly Interacting Massive Particles

在COUPP项目(芝加哥地下粒子物理观测站)中，已经证明了在大体积(即气泡室)中使用室温中等过热液体进行罕见事件搜索的可能性。开发的原型室表现出稳定的行为，通过仔细选择工作温度和压力，目标液体可以使其对低能核反冲敏感，就像弱相互作用大质量粒子(WIMP)所预期的那样，同时对最小的电离粒子保持不敏感：COUPP室具有无与伦比的伽马抑制系数。在这项提议中，国际和平研究所要求提供资金，以支持在本提议所涉期间在地下实验室之一部署5个50公斤重的小暗室，总重量为250公斤。所使用的目标液体CF3I是一种安全的工业制冷剂，通常用作灭火器，同时对自旋相关和独立的最轻超对称伙伴联轴节同时最敏感。所提出的探测器系综具有相当于约550公斤Ge的与自旋无关的势能灵敏度，并且可以同时提高目前对与自旋相关的耦合的灵敏度，以至于将沿着两个前沿探测超对称模型。COUPP的目的不仅仅是改善当今WIMP的敏感性，而且还旨在实施各种目标和方法，这些目标和方法能够提供令人信服的证据，表明最终的信号来自WIMP，而不是一些不可还原的背景。这项研究将继续为本科生提供多种参与机会。还在开发使用稳定的、结构简单的微型气泡室作为背景不敏感、高效的快中子监测仪，用于货物集装箱的门户监测。

The possibility of using room-temperature moderately superheated liquids in the bulk (i.e., bubble chambers) for rare event searches has been demonstrated within the COUPP project (Chicagoland Observatory for Underground Particle Physics). The prototype chambers developed display a stable behavior and by careful selection of operating temperature and pressure, the target liquid can be made sensitive to low-energy nuclear recoils like those expected from Weakly Interacting Massive Particles (WIMPs), while remaining insensitive to minimum ionizing particles: an unparalleled gamma rejection factor has been demonstrated for COUPP chambers. In this proposal, the PI requests funds for support towards a 250 kg total mass in the form of five small 50 kg chambers, to be deployed in one of the underground laboratories during the period covered by this proposal. The target liquid employed, CF3I, a safe industrial refrigerant commonly used as a fire extinguisher, is simultaneously maximally sensitive to both spin-dependent and -independent Lightest Supersymmetric Partner couplings. The proposed detector ensemble features a spin-independent potential sensitivity equivalent to ~550 kg of Germanium, and can simultaneously improve the present sensitivity to spin-dependent couplings to the point that supersymmetric models will be probed along both fronts. COUPP aims not at a mere improvement of present-day WIMP sensitivity, but also at implementing a variety of targets and methods able to provide convincing evidence that an eventual signal arises from WIMPs and not some irreducible background. This research will continue to provide multiple opportunities for undergraduate involvement. The use of stable, structurally simple mini-bubble chambers as background-insensitive, high-efficiency fast neutron monitors for portal monitoring of cargo containers is also being developed.