PandaX is a large liquid-xenon detector experiment usable for direct dark-matter detection and 136Xe double-beta decay search.The central vessel was designed to accommodate a staged target volume increase from initial...PandaX is a large liquid-xenon detector experiment usable for direct dark-matter detection and 136Xe double-beta decay search.The central vessel was designed to accommodate a staged target volume increase from initially 120 kg(stage I)to 0.5 t(stage II)and eventually to a multi-ton scale.The experiment is located in the Jinping Deep-Underground Laboratory in Sichuan,China.The detector operates in dual-phase mode,allowing detection of both prompt scintillation,and ionization charge through proportional scintillation.In this paper a detailed description of the stage I detector design and performance as well as results established during the commissioning phase are presented.展开更多
We present a systematic determination of the responses of PandaX-Ⅱ,a dual phase xenon time projection chamber detector,to low energy recoils.The electron recoil(ER) and nuclear recoil(NR) responses are calibrated,res...We present a systematic determination of the responses of PandaX-Ⅱ,a dual phase xenon time projection chamber detector,to low energy recoils.The electron recoil(ER) and nuclear recoil(NR) responses are calibrated,respectively,with injected tritiated methane or 220Rn source,and with 241Am-Be neutron source,in an energy range from 1-25 keV(ER) and 4-80 keV(NR),under the two drift fields,400 and 317 V/cm.An empirical model is used to fit the light yield and charge yield for both types of recoils.The best fit models can describe the calibration data significantly.The systematic uncertainties of the fitted models are obtained via statistical comparison to the data.展开更多
We report the Neutrino-less Double Beta Decay（NLDBD） search results from PandaX-Ⅱ dual-phase liquid xenon time projection chamber.The total live time used in this analysis is 403.1 days from June 2016 to August2018...We report the Neutrino-less Double Beta Decay（NLDBD） search results from PandaX-Ⅱ dual-phase liquid xenon time projection chamber.The total live time used in this analysis is 403.1 days from June 2016 to August2018.With NLDBD-optimized event selection criteria,we obtain a fiducial mass of 219 kg of natural xenon.The accumulated xenon exposure is 242 kg yr,or equivalently 22.2 kg yr of 136Xe exposure.At the region around 136Xe decay Q-value of 2458 keV,the energy resolution of PandaX-Ⅱ is 4.2%.We find no evidence of NLDBD in PandaX-Ⅱand establish a lower limit for decay half-life of 2.1×1023yr at the 90% confidence level,which corresponds to an effective Majorana neutrino mass mββ <（1.4-3.7） eV.This is the first NLDBD result reported from a dual-phase xenon experiment.展开更多
The two-phase xenon detector is at the frontier of dark matter direct search. This kind of detector uses liquid xenon as the sensitive target and is operated in two-phase （liquid/gas） mode, where the liquid level ne...The two-phase xenon detector is at the frontier of dark matter direct search. This kind of detector uses liquid xenon as the sensitive target and is operated in two-phase （liquid/gas） mode, where the liquid level needs to be monitored and controlled in sub-millimeter precision. In this paper, we present a detailed design and study of two kinds of level meters for the PandaX dark matter detector. The long level meter is used to monitor the overall liquid level while short level meters are used to monitor the inclination of the detector. These level meters are cylindrical capacitors that are custom-made from two concentric metal tubes. Their capacitance values are read out by a universal transducer interface chip and are recorded by the PandaX slow control system. We present the developments that lead to level meters with long-term stability and sub-millimeter precision. Fluctuations （standard deviations） of less than 0.02 mm for the short level meters and less than 0.2 mm for the long level meter were achieved during a few days of test operation.展开更多
Neutrinos from core-collapse supernovae are essential for understanding neutrino physics and stellar evolution.Dual-phase xenon dark matter detectors can be used to track explosions of galactic supernovae by detecting...Neutrinos from core-collapse supernovae are essential for understanding neutrino physics and stellar evolution.Dual-phase xenon dark matter detectors can be used to track explosions of galactic supernovae by detecting neutrinos through coherent elastic neutrino-nucleus scatterings.In this study,a variation of progenitor masses and explosion models are assumed to predict neutrino fluxes and spectra,which result in the number of expected neutrino events ranging from 6.6 to 13.7 at a distance of 10 kpc over a 10-s duration with negligible backgrounds at PandaX-4T.Two specialized triggering alarms for monitoring supernova burst neutrinos are built.The efficiency of detecting supernova explosions at various distances in the Milky Way is estimated.These alarms will be implemented in the real-time supernova monitoring system at PandaX-4T in the near future,which will provide supernova early warnings for the astronomical community.展开更多
Panda X是一个利用惰性元素"氙"作为探测介质进行粒子及天体物理稀有事件探测的大型实验装置.Panda X的一期和二期实验主要利用"二相型氙"时间投影室技术来进行弱相互作用暗物质粒子的直接探测.其中一期实验使用了1...Panda X是一个利用惰性元素"氙"作为探测介质进行粒子及天体物理稀有事件探测的大型实验装置.Panda X的一期和二期实验主要利用"二相型氙"时间投影室技术来进行弱相互作用暗物质粒子的直接探测.其中一期实验使用了120 kg氙,目标是在低质量暗物质区域检验以往其他实验所发现的疑似信号.一期实验的结果不支持这些疑似信号,并对10 Ge V/c2以下质量的暗物质性质给出了严格的限制.二期实验升级后的探测器使用了500 kg的氙.二期实验目前正在进行调试和试运行,它将在2015年末正式开始数据采集.Panda X第三期实验将采用高压的富氙-136(90%富集度)气体探测器进行无中微子双贝塔衰变探测,以研究中微子的本质.三期实验正在进行概念设计和原型测试.展开更多
We report the dark matter search results obtained using the full 132 ton·day exposure of the PandaX-II experiment,including all data from March 2016 to August 2018.No significant excess of events is identified ab...We report the dark matter search results obtained using the full 132 ton·day exposure of the PandaX-II experiment,including all data from March 2016 to August 2018.No significant excess of events is identified above the expected background.Upper limits are set on the spin-independent dark matter-nucleon interactions.The lowest 90%confidence level exclusion on the spin-independent cross section is 2.2×10−46 cm2 at a WIMP mass of 30 GeV/c2.展开更多
基金supported by a 985 grant from Shanghai Jiao Tong Universitythe National Basic Research Program of China (Grant No. 2010CB833005)+4 种基金the National Natural Science Foundation of China (Grant No. 11055003)the Office of Science and Technology in Shanghai Municipal Government (Grant No. 11DZ2260700)sponsored by Shandong University, Peking Universitythe University of Marylandthe University of Michigan
文摘PandaX is a large liquid-xenon detector experiment usable for direct dark-matter detection and 136Xe double-beta decay search.The central vessel was designed to accommodate a staged target volume increase from initially 120 kg(stage I)to 0.5 t(stage II)and eventually to a multi-ton scale.The experiment is located in the Jinping Deep-Underground Laboratory in Sichuan,China.The detector operates in dual-phase mode,allowing detection of both prompt scintillation,and ionization charge through proportional scintillation.In this paper a detailed description of the stage I detector design and performance as well as results established during the commissioning phase are presented.
基金Supported by a grant from the Ministry of Science and Technology of China(2016YFA0400301)National Science Foundation of China(12090060,11525522,11775141,11755001)Office of Science and Technology,Shanghai Municipal Government(18JC1410200)。
文摘We present a systematic determination of the responses of PandaX-Ⅱ,a dual phase xenon time projection chamber detector,to low energy recoils.The electron recoil(ER) and nuclear recoil(NR) responses are calibrated,respectively,with injected tritiated methane or 220Rn source,and with 241Am-Be neutron source,in an energy range from 1-25 keV(ER) and 4-80 keV(NR),under the two drift fields,400 and 317 V/cm.An empirical model is used to fit the light yield and charge yield for both types of recoils.The best fit models can describe the calibration data significantly.The systematic uncertainties of the fitted models are obtained via statistical comparison to the data.
基金Supported by grants from the Ministry of Science and Technology of China(2016YFA0400301,2016YFA0400302)a Double Top-class grant from Shanghai Jiao Tong University,grants from National Science Foundation of China(11435008,11505112,11525522,11775142,11755001)+3 种基金grants from the Office of Science and Technology,Shanghai Municipal Government(11DZ2260700,16DZ2260200,18JC1410200)the support from the Key Laboratory for Particle Physics,Astrophysics and Cosmology,Ministry of Educationsupported in part by the Chinese Academy of Sciences Center for Excellence in Particle Physics(CCEPP)Hongwen Foundation in Hong Kong
文摘We report the Neutrino-less Double Beta Decay（NLDBD） search results from PandaX-Ⅱ dual-phase liquid xenon time projection chamber.The total live time used in this analysis is 403.1 days from June 2016 to August2018.With NLDBD-optimized event selection criteria,we obtain a fiducial mass of 219 kg of natural xenon.The accumulated xenon exposure is 242 kg yr,or equivalently 22.2 kg yr of 136Xe exposure.At the region around 136Xe decay Q-value of 2458 keV,the energy resolution of PandaX-Ⅱ is 4.2%.We find no evidence of NLDBD in PandaX-Ⅱand establish a lower limit for decay half-life of 2.1×1023yr at the 90% confidence level,which corresponds to an effective Majorana neutrino mass mββ <（1.4-3.7） eV.This is the first NLDBD result reported from a dual-phase xenon experiment.
基金Supported by National Science Foundation of China(11055003,11175117)Science and Technology Commission of Shanghai Municipality(11PJ1405300)Ministry of Science and Technology of China(2010CB833005)
文摘The two-phase xenon detector is at the frontier of dark matter direct search. This kind of detector uses liquid xenon as the sensitive target and is operated in two-phase （liquid/gas） mode, where the liquid level needs to be monitored and controlled in sub-millimeter precision. In this paper, we present a detailed design and study of two kinds of level meters for the PandaX dark matter detector. The long level meter is used to monitor the overall liquid level while short level meters are used to monitor the inclination of the detector. These level meters are cylindrical capacitors that are custom-made from two concentric metal tubes. Their capacitance values are read out by a universal transducer interface chip and are recorded by the PandaX slow control system. We present the developments that lead to level meters with long-term stability and sub-millimeter precision. Fluctuations （standard deviations） of less than 0.02 mm for the short level meters and less than 0.2 mm for the long level meter were achieved during a few days of test operation.
基金the National Natural Science Foundation of China(12090060,12090063,12105052,12005131,11905128,11925502)the Office of Science and Technology,Shanghai Municipal Government,China(22JC1410100)。
文摘Neutrinos from core-collapse supernovae are essential for understanding neutrino physics and stellar evolution.Dual-phase xenon dark matter detectors can be used to track explosions of galactic supernovae by detecting neutrinos through coherent elastic neutrino-nucleus scatterings.In this study,a variation of progenitor masses and explosion models are assumed to predict neutrino fluxes and spectra,which result in the number of expected neutrino events ranging from 6.6 to 13.7 at a distance of 10 kpc over a 10-s duration with negligible backgrounds at PandaX-4T.Two specialized triggering alarms for monitoring supernova burst neutrinos are built.The efficiency of detecting supernova explosions at various distances in the Milky Way is estimated.These alarms will be implemented in the real-time supernova monitoring system at PandaX-4T in the near future,which will provide supernova early warnings for the astronomical community.
基金Supported by a Double Top-class grant from Shanghai Jiao Tong University,grants from National Science Foundation of China(11435008,11525522,11775141,11755001)a grant from the Ministry of Science and Technology of China(2016YFA0400301)the Office of Science and Technology,Shanghai Municipal Government(11DZ2260700,16DZ2260200,18JC1410200)。
文摘We report the dark matter search results obtained using the full 132 ton·day exposure of the PandaX-II experiment,including all data from March 2016 to August 2018.No significant excess of events is identified above the expected background.Upper limits are set on the spin-independent dark matter-nucleon interactions.The lowest 90%confidence level exclusion on the spin-independent cross section is 2.2×10−46 cm2 at a WIMP mass of 30 GeV/c2.
