NEWS-G Search for Light Dark Matter with Spherical Proportional Counters

NEWS-G 用球形正比计数器搜索光暗物质

• 批准号: SAPPJ-2020-00033
• 负责人: Giroux, Guillaume
• 金额: $ 18.21万
• 依托单位: Queen's University
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Project
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=763247
• 关键词: NEWS; Search; Light; Dark; Matter

Despite the overwhelming amount of astronomical and cosmological evidences for dark matter in the universe, its unknown nature is arguably the most pressing question of modern physics. WIMPs (Weakly Interacting Massive Particles) are a class of candidates emerging from beyond-the-Standard-Model frameworks that have been favoured so far. The 10 GeV to 10 TeV-mass WIMPs predicted by many well-motivated SUSY (supersymmetric) models have so far not been found by dark matter search experiments. This, combined with the lack of evidence for SUSY at the LHC (Large Hadron Collider), warrants for the extension of the search to lower WIMP masses. The motivation for this search is further strengthened by new theories predicting low-mass WIMPs such as asymmetric dark matter and dark sectors. The aim of the NEWS-G (New Experiment With Spheres - Gas) collaboration is the discovery of low-mass dark matter particles (< 1 GeV) using ultra-low background spherical proportional counters (SPC). SPCs are spherical gaseous detectors operated in proportional mode. A small sensor, held at high voltage at the centre of a grounded spherical shell, is drifting the primary ionization created by the interaction of a particle with the gaseous target. As the free charge approaches the sensor, the electric field becomes large enough to create an avalanche process. Sensitivity to single electrons, corresponding to an energy threshold of a few 10's of eV, is made possible by the high amplification gain and low intrinsic capacitance of the sensor. This, combined with the use of light target gases such as hydrogen, helium and neon which allows for the optimization of momentum transfer with low-mass WIMPs, makes the SPC a powerful tool in the search for WIMPs with masses below 1 GeV. The NEWS-G collaboration is comprised of 43 scientists from 11 institutions in Canada (Queen's University, SNOLAB/Laurentian University, TRIUMF, University of Alberta), France (LSM, CEA IRFU, LPSC Grenoble), Greece (Aristotle University of Thessaloniki), United Kingdom (University of Birmingham) and USA (PNNL). WIMP search results were recently reported by the collaboration using SEDINE, a 60-cm diameter prototype SPC installed at the Laboratoire Souterrain de Modane (LSM) in France. These results demonstrate the SPC operation at low energy threshold with a neon-methane mixture and at the time of publication were giving the most stringent limits on the WIMP-nucleus spin-independent cross-section for WIMP masses below 0.6 GeV. The competitive results obtained with SEDINE are promising for the next phase of the NEWS-G experiment: a 140-cm diameter SPC to be installed at SNOLAB in early 2020. Thanks to enhanced background control, sensor development and novel detector monitoring techniques, NEWS-G at SNOLAB is set to improve its sensitivity by a factor 1000 and is poised to obtain the world's best sensitivity to WIMP masses below 1 GeV.

尽管有大量的天文和宇宙学证据证明宇宙中存在暗物质，但其未知的性质可以说是现代物理学最紧迫的问题。WIMPS(弱相互作用的大质量粒子)是一类出现在超越标准模型框架中的候选粒子，到目前为止一直受到青睐。到目前为止，许多动机良好的超对称模型预测的10GeV到10TeV质量的WIMP还没有被暗物质搜索实验发现。这一点，再加上在LHC(大型强子对撞机)上缺乏SUSY的证据，有理由将搜索范围扩大到较低的WIMP质量。预测低质量WIMP的新理论进一步加强了这种探索的动机，例如不对称暗物质和暗扇区。NEWS-G(球体气体新实验)合作的目的是使用超低本底球面正比计数器(SPC)发现低质量暗物质粒子(&lt；1GeV)。SPC是以比例模式工作的球形气体探测器。在接地球壳的中心，一个保持高压的小型传感器正在漂移由粒子与气态目标相互作用产生的初级电离。当自由电荷接近传感器时，电场变得足够大，从而产生雪崩过程。传感器的高放大增益和低本征电容使得对单电子的灵敏度成为可能，对应于几个10‘S的电动汽车的能量阈值。这一点，再加上氢、氦和霓虹灯等轻目标气体的使用，使得SPC成为寻找质量低于1GeV的WIMP的强大工具，从而实现了低质量WIMP的动量传递优化。NEWS-G合作由来自加拿大(女王大学、SNOLAB/Laurentian大学、TRIUMF、阿尔伯塔大学)、法国(LSM、CEA IRFU、LPSC Grioble)、希腊(塞萨洛尼基亚里士多德大学)、英国(伯明翰大学)和美国(PNL)11个机构的43名科学家组成。WIMP搜索结果最近由合作使用SEDINE报告，SEDINE是安装在法国南莫丹实验室(LSM)的直径60厘米的SPC原型。这些结果表明，在低能量阈值下，SPC在Ne-甲烷混合物中运行，并且在本文发表时，对于小于0.6GeV的WIMP质量，给出了最严格的WIMP核自旋独立截面的限制。SEDINE获得的竞争性结果对NEWS-G实验的下一阶段很有希望：一个直径140厘米的SPC将于2020年初安装在SNOLAB。由于增强的背景控制、传感器开发和新颖的探测器监测技术，SNOLAB的NEWS-G将把其灵敏度提高1000倍，并有望获得世界上对1GeV以下WIMP质量的最佳灵敏度。