Collaborative Research: R & D Toward DarkSide-G2, a Second-Generation Direct Search for Dark Matter

暗物质的存在是从引力效应中得知的，但它的本质仍然是一个深谜。在基本粒子物理学中，有一种可能性是由其他考虑所激发的，即暗物质是由未被发现的基本粒子组成的；弱相互作用大质量粒子（wimp）是一种可能性。wimp可能构成暗物质的证据可能来自欧洲核子研究中心（CERN）的大型强子对撞机（Large Hadron Collider）的实验，或者来自探测星系晕中WIMP-WIMP湮灭产生的辐射的敏感天文仪器。构成银河系暗物质晕的大质量弱相互作用粒子的轨道运动应该会导致大质量弱相互作用粒子的核碰撞，其能量足以被灵敏的实验室设备观测到。该奖项将为支持DarkSide-G2的研究和开发步骤提供资金，这是第二代（“G2”）直接搜索WIMP，使用有效质量为3.3吨的液态氩气时间投影室（TPC）。液态氩能有效地将WIMP诱导的核反冲能量转化为电离和闪烁，是一种很有前途的WIMP探测介质。氩闪烁时间分布（“脉冲形状”）取决于电离粒子的类型，提供可用于抑制背景的粒子识别。这是所有暗物质探测器中最强大的背景排斥因素之一，当与电离测量相结合时，背景排斥甚至进一步增强。如果使用常压氩气，则吨级或更大的液态氩TPC的性能将受到39-Ar高衰减率的限制。DarkSide-G2将使用从地下来源收集的氩气，这些氩气的39-Ar含量至少比大气氩气低150倍。这些资金将允许小组进行必要的详细机械设计工作，以确保探测器的功能，开发必要的高压和数据采集元件，并开发和确定极端放射性探测器组件和必要的技术，以最大限度地提高实验的灵敏度。更广泛的影响：这项活动将以多种方式促进天体粒子物理学及其科学和教育使命的发展：(1)它将为学生提供持续的培训机会，他们将有机会为基础科学和高级工程领域的前沿项目做出贡献；(2)通过开发可应用于从国家安全到医学成像等领域的技术，使社会受益；(3)支持继续发展成功的e&o项目，如lngs -南达科他州-普林斯顿高中学生暑期学校。

The existence of dark matter is known from gravitational effects, but its nature remains a deep mystery. One possibility motivated by other considerations in elementary particle physics is that dark matter consists of undiscovered elementary particles; Weakly Interacting Massive Particles (WIMPs) are one possibility. Evidence for WIMPs that could constitute dark matter may come from experiments at the Large Hadron Collider at CERN or from sensitive astronomical instruments that detect radiation produced by WIMP-WIMP annihilations in galaxy halos. The orbital motion of the WIMPs composing the dark matter halo pervading the galaxy should result in WIMP-nuclear collisions of sufficient energy to be observable by sensitive laboratory apparatus. This award will provide funding for research and development steps to support DarkSide-G2, a second-generation ("G2") direct WIMP search using a liquid argon Time Projection Chamber (TPC) with an active mass of 3.3 tons. Liquid argon is a promising 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. This is one of the most powerful background rejection factors among all dark matter detectors, and when combined with the measurement of ionization, background rejection is even further enhanced. The performance of a ton-scale or larger liquid argon TPC would be limited by the high rate of 39-Ar beta decays if atmospheric argon was used. DarkSide-G2 will use argon collected from underground sources which has been shown to have 39-Ar content lower than atmospheric argon by at least a factor of 150. These funds will allow the groups to carry out the detailed mechanical design work necessary to ensure the functionality of the detector, develop necessary high voltage and data acquisition elements, and develop and identify the extremely radiopure detector components and techniques necessary to maximize the sensitivity of the experiment.Broader impacts: This activity will advance the development of astroparticle physics and its scientific and educational mission in a variety of ways: (1) it will offer a continuing opportunity for the training of students, who will have a chance to contribute a cutting-edge project in fundamental science and advanced engineering; (2) it will benefit society by developing techniques that could find application in areas ranging from national security to medical imaging; and (3) it will support continued development of successful E&O programs such as the LNGS-South Dakota-Princeton summer school for high school students.