A Search for Weakly-Interacting Particle Dark Matter with DarkSide

多项天文观测已经确定，宇宙中大约85%的物质不是由正常原子组成的，而是不发射或吸收光的未被检测到的基本“暗物质”粒子。破译这种所谓的暗物质的性质对宇宙学、天体物理学和高能粒子物理学具有根本的重要性。一个主要的假设是，它是由弱相互作用大质量粒子（WIMP）组成的，这些粒子是在大爆炸后产生的。如果WIMP是暗物质，那么它们在我们星系中的存在可能是通过位于地下深处的探测器中的原子核散射来检测的，以帮助排除宇宙射线造成的背景。对WIMP暗物质的直接探测将解决粒子物理学和宇宙学中的一个基本谜团，为了解宇宙的主要物质组成和粒子物理学标准模型之外的物理学提供了一个独特的窗口。该奖项将资助该小组继续参与意大利格兰萨索地下国家实验室的黑暗面-50（DS-50）暗物质实验。详细了解DS-50背景和性能是设计未来液氩（LAr）暗物质探测器的关键，该探测器对重WIMP具有更好的灵敏度。麻省大学致力于氡、α衰变和表面背景的研究，以最大限度地提高DS-50的物理输出，并了解这种未来更大探测器的放大意义。PI有各种各样的学生，研究生和本科生，在他的实验室从事硬件和软件项目。他们的工作超越了马萨诸塞大学的墙壁，因为他们在大多数情况下第一次体验粒子物理学的前沿研究。充分参与国际研究合作，他们有机会前往一流的科学实验室和机构，会见国际知名的同学和科学家，并有领先的实验动手经验。PI在促进其研究小组的多样性方面有着良好的记录。DS-50使用双相液氩时间投影室（LAr TPC）搜索WIMP，WIMP可以将存款能量存入闪烁和电离信号。利用核反冲和电子反冲的闪烁光的不同时间剖面（“脉冲形状”），DS-50已经证明β/γ背景抑制为1.5x10^7。DS-50的继续运行将包括在无背景暗物质搜索中电离信号的全部信息，对于100 GeV质量的WIMP，自旋无关的WIMP-核子截面灵敏度为~ 100 x ^-45 cm ^2。

Multiple astronomical observations have established that about 85% of the matter in the universe is not made of normal atoms, but must be otherwise undetected elementary "dark matter" particles that do not emit or absorb light. Deciphering the nature of this so-called Dark Matter is of fundamental importance to cosmology, astrophysics, and high-energy particle physics. A leading hypothesis is that it is comprised of Weakly Interacting Massive Particles, or WIMPs, that were produced moments after the Big Bang. If WIMPs are the dark matter, then their presence in our galaxy may be detectable via scattering from atomic nuclei in detectors located deep underground to help reject backgrounds due to cosmic rays. Direct detection of WIMP dark matter would solve a fundamental mystery in particle physics and cosmology, providing a unique window to learning about the primary matter constituent of the Universe and of physics beyond the Standard Model of particle physics. This award will fund the continued participation of this group in the DarkSide-50 (DS-50) Dark Matter experiment at the Gran Sasso underground national laboratory in Italy. A detailed understanding of the DS-50 backgrounds and performance is key to the design of future liquid argon (LAr) dark matter detectors with substantially better sensitivity for heavy WIMPs. The UMass effort is centered on studies of radon, alpha-decays, and surface backgrounds to maximize the DS-50 physics output and to understand scale-up implications for such future, larger detectors.The PI has a diverse population of students, graduate and undergraduate, working in his lab on hardware and software projects. Their work reaches beyond the UMass walls, as they experience research at the forefront of particle physics in most cases for the first time. Fully involved in international research collaborations, they have the opportunity to travel to prime science laboratories and institutions, meet fellow students and scientists of international renown, and have hands-on experiences on leading experiments. The PI has an established track record for promoting diversity in his research group.DS-50 searches for WIMPs with a dual-phase liquid argon Time Projection Chamber (LAr TPC) in which WIMPs could deposit energy into both scintillation and ionization signals. Exploiting the different time profile ("pulse shape") of the scintillation light of nuclear and electron recoils, DS-50 has demonstrated beta/gamma background suppression of 1.5x10^7. The continued run of DS-50 will include the full information of ionization signals in a background-free dark matter search with spin-independent WIMP-nucleon cross section sensitivity of ~­10x^-45 cm^2 for 100 GeV mass WIMPs.