Collaborative Research: Direct Search for Dark Matter with Underground Argon at LNGS

暗物质的存在是由引力效应推断出来的，但它的性质仍然是一个深层次的谜。一种可能性是，在基本粒子物理学的考虑下，暗物质由假设的弱相互作用大质量粒子(WIMP)组成。直接探测WIMP应该是可能的，因为组成遍布银河系的暗物质晕的WIMP的轨道运动应该会导致足够能量的WIMP-核碰撞，以便在实验室中观察到。这项合作利用资金委托和运营Darkside-50，这是一项使用液体Ar-TPC(液体Ar-TPC)的WIMP搜索，有效质量为50公斤。Darkside-50将使用从地下来源(地下Argon，UAR)提取的Ar-39，该小组已经证明，Ar-39的含量比大气中的Ar-39低至少150倍。AR-39是该实验的主要背景来源之一。该小组研究的一个重要副产品是开发技术，这些技术可能会在从国家安全到医学成像的领域得到应用。这源于从地下来源提取稀有稀有气体(Ar和He)，可能的应用包括地下核试验的探测和在环境科学中使用Ar作为探测介质，用于水文传输的环境无线电示踪剂的超低水平正比计数器测量。液态Ar是一种有吸引力的WIMP探测介质，因为它能有效地将WIMP引起的核反冲能量转换为电离和闪烁。Ar闪烁时间分布(“脉冲形状”)取决于电离粒子的类型，从而提供可用于抑制背景的粒子辨别。Ar中的脉冲形状识别提供了所有暗物质技术中最强大的背景拒绝之一；当与电离测量相结合时，背景拒绝进一步增强。拟议的活动将通过以下方式推动天体粒子物理学的发展及其科学和教育使命：(1)为学生提供持续良好的培训机会，他们将为尖端项目的成功做出贡献；(2)开发能够在几个有益于社会的领域得到应用的技术；以及(3)支持一项新的教育和推广计划，该计划旨在接替非常成功的实验室-南达科他州-普林斯顿纳齐奥利-德尔格兰萨索暑期学校。

The existence of dark matter is inferred from gravitational effects, but its nature remains a deep mystery. One possibility, motivated by considerations in elementary particle physics, is that dark matter consists of the hypothesized Weakly Interacting Massive Particles (WIMPs). It should be possible to detect WIMPs directly, as the orbital motion of the WIMPs composing the dark matter halo pervading the galaxy should result in WIMP-nucleus collisions of sufficient energy to be observable in the laboratory. This collaboration utilizes funds to commission and operate DarkSide-50, a WIMP search using a Liquid Argon Time Projection Chamber (LAr-TPC) with an active mass of 50 kg. DarkSide-50 will use argon extracted from underground sources (Underground Argon, UAr), which this group has shown to have an Ar-39 content lower, by at least a factor of 150, than atmospheric argon. Ar-39 is one of the main sources of background in the experiment.A significant by-product of this group's research has been developing techniques that could find application in areas ranging from national security to medical imaging. This arises from the extraction of rare noble gases (Argon and Helium) from underground sources, and possible applications include the detection of underground nuclear tests and in Environmental Science where Argon is used as a detection media in ultra-low level proportional counter measurements for an environmental radio tracer for hydrologic transport.Liquid argon is an attractive medium for WIMP detection due to its efficient conversion of energy from WIMP-induced nuclear recoils into both ionization and scintillation. The argon scintillation time profile ("pulse shape") depends on the type of ionizing particle, providing particle discrimination that can be used to suppress background. Pulse shape discrimination in argon provides one of the most powerful background rejections among all dark matter technologies; when combined with the measurement of ionization, the background rejection is further enhanced. The proposed activity will advance the development of astroparticle physics and its scientific and educational mission by: (1) offering a continuing excellent opportunity for the training of students, who will contribute to the success of a cutting-edge project; (2) developing techniques that could find application in several areas of benefit to society; and (3) supporting a new education and outreach program, designed to succeed the highly successful Laboratori Nazionali del Gran Sasso-South Dakota-Princeton summer school.