Search for Dark Matter with PICO

PICO是一个由来自加拿大、美国、墨西哥、西班牙、印度和捷克共和国的科学家和工程师组成的国际合作组织。加拿大在这个项目上处于领先地位，该项目旨在利用位于加拿大SNOLAB天体粒子物理设施深处的复杂气泡室来搜索暗物质。几十年来，科学家们已经知道，宇宙中近85%的物质是地球上从未直接观察到的形式。这种物质被认为在整个银河系中无处不在，但它与正常物质的相互作用非常罕见，以至于迄今为止从未被观测到。气泡室中含有一种处于亚稳态的过热状态的流体，当最微小的能量储存在气泡室中时，这种流体可能会开始沸腾。如果暗物质粒子在敏感体积内散射，反冲核将触发容易观察到的相变。Pico用一组快速相机观察到初始气泡的形成，由于成核过程伴随着一小串声音，探测器周围环绕着灵敏的压电式传感器。所有暗物质探测器的祸害是存在由自然放射性产生的信号，这种信号可以模仿暗物质信号。Pico在世界上是独一无二的，它对光子、电子、阿尔法粒子和中子具有出色的背景抑制能力，该实验位于地下深处，以躲避地球表面普遍存在的宇宙射线。 皮科拥有发现暗物质的能力，或者说排除了许多描述其性质的理论。Pico已经对可能的相互作用强度设定了世界领先的限制，通过这笔赠款提供的资金，将能够充分探索许多理论预测的暗物质参数空间区域。随着新探测器的覆盖范围扩大，这些探测器将使用本申请所需的资金进行操作，人们非常乐观地认为，暗物质可能即将发现。 暗物质本质的发现是当今物理学最优先考虑的问题之一。众所周知，暗物质影响宇宙结构的形成，是宇宙学模型中的一个重要因素。对暗物质及其与正常物质相互作用方式的理解将塑造我们的基本粒子物理、天体物理和宇宙学理论。

PICO is an international collaboration consisting of scientists and engineers from Canada, the USA, Mexico, Spain, India, and the Czech Republic. Canada is a leader on this project which aims to search for Dark Matter using sophisticated Bubble Chambers located deep underground in the Canadian SNOLAB facility for astroparticle physics. Scientists have known for decades that nearly 85% of the matter in the Universe is in a form never directly observed on Earth. This matter is believed to be ubiquitous throughout the galaxy, but has interactions with normal matter so rarely that it has never been observed to date.Bubble Chambers contain a fluid in a metastable superheated state that may begin to boil when the tiniest amount of energy is deposited within the chamber. If a dark matter particle scatters within the sensitive volume, the recoiling nucleus will trigger a phase transition that is readily observable. PICO observes the initial bubble formation with an array of fast cameras, and as the nucleation is accompanied by a small burst of sound, sensitive piezo electric sensors surround the detector. The bane of all dark matter detectors is the presence of signals produced by natural radioactivity that can mimic the dark matter signal. PICO is unique in the world with its excellent background rejection capability for photons, electrons, alpha particles and neutrons, and the experiment is located deep underground to evade the cosmic rays that are prevalent at the surface of the Earth. PICO has the capability of discovering dark matter, or ruling out many of the theories describing its nature. PICO has already set world leading limits on the possible interaction strength, and with the funds provided through this grant, will be able to fully explore the region of parameter space many theories predict for dark matter. With the extended reach of the new detectors that will be operated with funds requested in this application, there is great optimism that a dark matter discovery may be near. The discovery of the nature of dark matter is one of the highest priorities in physics today. The dark matter is known to influence the formation of structures in the Universe and is an important factor in cosmological models. An understanding of dark matter and the way it interacts with normal matter will shape our theories of fundamental particle physics, astrophysics, and cosmology.