We propose a major upgrade to the existing PandaX-4T experiment in the China Jinping Underground Laboratory. The new experiment, PandaX-xT, will be a multi-ten-tonne liquid xenon, ultra-low background, and general-purpose observatory. The full-scaled PandaX-xT contains a 43-tonne liquid xenon active target. Such an experiment will significantly advance our fundamental understanding of particle physics and astrophysics. The sensitivity of dark matter direct detection will be improved by nearly two orders of magnitude compared to the current best limits, approaching the so-called "neutrino floor" for a dark matter mass above 10 GeV/$c^2$, providing a decisive test to the Weakly Interacting Massive Particle paradigm. By searching for the neutrinoless double beta decay of $^{136}$Xe isotope in the detector, the effective Majorana neutrino mass can be measured to a [10 -- 41] meV/$c^2$ sensitivity, providing a key test to the Dirac/Majorana nature of neutrino s. Astrophysical neutrinos and other ultra-rare interactions can also be measured and searched for with an unprecedented background level, opening up new windows of discovery. Depending on the findings, PandaX-xT will seek the next stage upgrade utilizing isotopic separation on natural xenon.
Search for Diffuse Supernova Neutrino Background of All Flavors with PandaX-4T
Research Center for Particle Science and Technology, Institute of Frontier and Interdisciplinary Science, Shandong University（山东大学前沿交叉科学研究院粒子科学与技术研究中心）；Key Laboratory of Particle Physics and Particle Irradiation of the Ministry of Education, Shandong University（山东大学教育部粒子物理与粒子辐照重点实验室）；State Key Laboratory of Dark Matter Physics, Key Laboratory for Particle Astrophysics and Cosmology (MoE), Shanghai Key Laboratory for Particle Physics and Cosmology, School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院暗物质物理全国重点实验室粒子天体物理与宇宙学教育部重点实验室上海市粒子物理与宇宙学重点实验室）；New Cornerstone Science Laboratory, Tsung-Dao Lee Institute, Shanghai Jiao Tong University（上海交通大学新Cornerstone科学实验室汤川秀树研究所）；Shanghai Jiao Tong University Sichuan Research Institute（上海交通大学四川研究院）
GPS-Synchronized Monitoring of Core-collapse Supernova Bursts with PandaX-4T via Coherent Elastic Neutrino Nuclear Scattering
Research Center for Particle Science and Technology, Institute of Frontier and Interdisciplinary Science, Shandong University（山东大学前沿交叉科学研究院粒子科学与技术研究中心）；Key Laboratory of Particle Physics and Particle Irradiation of Ministry of Education, Shandong University（山东大学教育部粒子物理与粒子辐照重点实验室）；State Key Laboratory of Dark Matter Physics, Key Laboratory for Particle Astrophysics and Cosmology (MoE), Shanghai Key Laboratory for Particle Physics and Cosmology, School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院暗物质物理国家重点实验室粒子天体物理学与宇宙学教育部重点实验室上海粒子物理与宇宙学重点实验室）；Shanghai Jiao Tong University Sichuan Research Institute（上海交通大学四川研究院）；Jinping Deep Underground Frontier Science and Dark Matter Key Laboratory of Sichuan Province（四川省深地前沿科学与暗物质重点实验室）；Yalong River Hydropower Development Company, Ltd.（雅砻江流域水电开发有限公司）
Measurement of solar $pp$ neutrino flux with the new PandaX-4T data
Shanghai Jiao Tong University（上海交通大学）；Jinping Deep Underground Frontier Science and Dark Matter Key Laboratory of Sichuan Province（四川省锦屏深地前沿科学与暗物质重点实验室）；Yalong River Hydropower Development Company, Ltd.（雅砻江流域水电开发有限公司）
