The XENON1T Dark Matter Project: A Project Proposal from the US Institutions of the XENON Collaboration

这项研究项目利用两相液态氙气(LXE)时间投影室(LXeTPC)作为氙气阶段计划的一部分，通过寻找弱相互作用质量粒子(WIMP)来解决银河系暗物质的性质问题。XENON100建立在XENON10原型的成功基础上，代表了WIMP搜索检测器的当前最先进水平。凭借现实的发现潜力，XENON100已经达到了世界领先的灵敏度，并继续在意大利国家实验室(LNGS)积累数据，以达到其最终的灵敏度范围。为了充分探索WIMP暗物质的一个特别有利的电弱物理区域，以寻找第一个强大的和具有统计意义的发现，Xe计划的下一阶段将是一个吨级的探测器-XENON1T。LXeTPC的显着进步和进化极大地加速了世界范围内直接探测暗物质的竞赛。他们将目标质量的范围从几公斤转移到几十公斤，同时将电子和核反冲背景降低到极低的水平。氙气的合作已经证明了LXeTPC的有效缩放，其相控探测器的灵敏度至少增加了一个数量级，并准备转移到吨级。该合同将为美国集团建造XENON1T探测器、低温基础设施和校准系统提供资金。本实验基于一台用低放射性光电倍增管观察到的2.2吨LXE的TPC。通过利用LXeTPC出色的自我屏蔽和3D位置分辨率，通过选择现有的低放射性探测器材料，并通过将探测器放置在大型活性水盾和切伦科夫介子否决权中，1.1吨基准目标内的总体事故率估计比XENON100测量的本底低100倍以上。这一速度意味着在WIMP搜索区域每年每吨不到一次事件-对于暗物质实验来说，这是史无前例的低本底水平。广泛影响：探测宇宙中缺失质量的氙气科学目标具备所有成分来吸引学生和普通公众的兴趣和想象力。该项目的技术进步可以在许多方面影响社会：液体氙气成像探测器和相关技术在粒子天体物理以外的几个领域得到应用，包括国土安全和医学成像研究。

This research project addresses the question of the nature of galactic dark matter with a search for Weakly Interacting Massive Particles (WIMPs), using two-phase liquid xenon (LXe) Time Projection Chambers (LXeTPCs) as part of the XENON phased program. XENON100, building upon the success of the XENON10 prototype, represents the current state-of-the-art in WIMP search detectors. With a realistic discovery potential, XENON100 has already reached a world-leading sensitivity, and continues to accrue data at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy towards its ultimate sensitivity reach. To fully probe a particularly favorable region of electroweak physics for WIMP dark matter in search of a first robust and statistically significant discovery, the next phase of the XENON program will be a detector at the ton scale - XENON1T. The worldwide race towards direct dark matter detection has been dramatically accelerated by the remarkable progress and evolution of LXeTPCs. They have shifted the scale of target mass from a few to tens of kilograms whilst simultaneously reducing both electronic and nuclear recoil backgrounds to extremely low levels. The XENON collaboration has demonstrated the effective scaling of LXeTPCs with phased detectors of increasing sensitivity of at least an order of magnitude, and is ready to move to the ton scale. This award will provide funding to the US groups for the construction of the XENON1T detector, cryogenics infrastructure and calibration systems. This experiment is based on a TPC with 2.2 ton of LXe viewed by low radioactivity photomultiplier tubes. By exploiting the excellent self-shielding and 3D position resolution of a LXeTPC, by selecting existing low radioactivity detector materials and by placing the detector in a large active water shield and Cherenkov muon veto, the overall event rate within the fiducial target of 1.1 ton is estimated to be over a factor of 100 lower than the background measured in XENON100. This rate translates to less than one event per ton per year in the WIMP search region - an unprecedented low background level for a dark matter experiment.Broader Impact: The XENON scientific goal to detect the missing mass in the Universe has all the ingredients to captivate the interests and imagination of students and the general public alike. The technological advances of this project can impact society in a number of ways: liquid xenon imaging detectors and related technologies find applications in several fields outside particle astrophysics, including homeland security and medical imaging research.