LZD Development: the LUX-ZEPLIN Multi Tonne Dark Matter Experiment Technical Development Plan for DUSEL

暗物质的发现对宇宙学、天体物理学和基本粒子物理学具有根本性的重要性。广泛的观察表明，宇宙中80%到90%的物质是以某种新形式存在的。由此得出的标准宇宙学认为，宇宙能量密度的四分之一是一种尚未在实验室中遇到的新的基本形式的物质，其余的大部分是暗能量。这个谜题的答案可能在于存在某种新的通用类弱相互作用大质量粒子（wimp），它们的存在也受到粒子相互作用标准模型之外的物理学的推动。WIMP探测实验需要在地下深处进行，以防止宇宙射线相互作用产生假阳性信号。LUX和ZEPLIN合作，基于他们在液态氙（LXe）暗物质探测器方面的开创性努力，以及他们在低背景技术和罕见事件搜索方面的广泛专业知识，在这里提出了一个20吨LXe探测器（LZ20）的设计计划。LZ20探测器将采用已建立的两相LXe技术，通过读取初级和次级闪烁信号进行粒子识别，并进行三维位置重建，利用LXe的自屏蔽、去除表面伪影和校准位置相关响应函数。该探测器安装在4850级，基准质量为13.5吨，初始工作周期为1000天，将电磁和中子相互作用的内部和外部背景抑制到单个事件以下，对wimp相互作用的灵敏度降低到10的负48平方厘米的横截面。在这种曝光下，灵敏度将开始遇到来自太阳和大气中微子相互作用的不可还原背景。因此，这个实验代表了可以用液态Xe进行的决定性的WIMP搜索。关于更广泛的影响暗物质科学对公众有着广泛的吸引力，建立在公众的自然好奇心以及与重力的联系和熟悉之上。这次合作提议开展一系列活动，从参观和展示到与当地学校和个人的合作，以培养人们对科学和科学事业的兴趣。暗物质实验需要开发对辐射超敏感的新技术，以及实现超低放射性背景的新方法。这些技术和方法与广泛的核安全环境中使用的技术和方法有重叠之处。通过直接的技术开发或通过人员的培训，在他们的职业生涯后期转移到工业或国防实验室，合作预计LZ20将产生重大影响，特别是因为LLNL的参与。本提案包括博士后指导计划的描述。

The discovery of dark matter is of fundamental importance to cosmology, astrophysics, and elementary particle physics. A broad range of observations indicate that 80 to 90% of the matter in the universe is in some new form of matter. The resulting Standard Cosmology holds that a quarter of the energy density of the universe is a new fundamental form of matter not yet encountered in the laboratory, and most of the remainder is dark energy. The solution to this mystery may lie in the existence of some new generic class of Weakly Interacting Massive Particles, or WIMPs, whose existence is also motivated by physics beyond the standard model of particle interactions. WIMP detection experiments require operation deep underground to prevent cosmic ray interactions from causing false positive signals. The LUX and ZEPLIN collaborations, building on their pioneering efforts in liquid xenon (LXe) dark matter detectors and their broad expertise in low background techniques and rare event searches, propose here a plan for the design of a 20-ton LXe detector (LZ20). The LZ20 detector will use established two-phase LXe technology with readout of primary and secondary scintillation signals for particle identification together with 3d position reconstruction to exploit the self-shielding of the LXe, removal of surface artifacts and calibration of position dependent response functions. This detector, installed at the 4850 level, with a fiducial mass of 13.5 tons and an initial operating period of 1000 days, will suppress internal and external backgrounds from electromagnetic and neutron interactions to below a single event and achieve a sensitivity to WIMP-interactions down to cross section of 10 to the power negative 48 cm2. At this exposure, the sensitivity will begin to encounter irreducible backgrounds from solar and atmospheric neutrino interactions this experiment therefore represents the definitive WIMP search that can be performed with liquid Xe.Regarding Broader Impacts Dark Matter science is broadly appealing to the public, building on the natural curiosity of the public as well as the connection and familiarity with gravity. The collaboration proposes to develop a range of activities, from tours and displays to partnerships with local schools and individuals, to foster an interest in science and science careers. Dark matter experiments demand the development of new technologies that are ultra-sensitive to radiation, and new methods for achieving ultra-low radioactive backgrounds. There is an overlap of these technologies and methods with those used in a wide range of nuclear security contexts. Through direct technology development or through the training of personnel that transfer to industry or defense labs later in their careers, the collaboration expects significant impact from LZ20 particularly because of the involvement of LLNL. This proposal includes a description of postdoctoral mentoring plans.