The proton-proton(pp)fusion chain dominates the neutrino production in the Sun.The uncertainty of the predicted pp neutrino flux is at the sub-percent level,whereas that of the best measurement is O(10%).In this study...The proton-proton(pp)fusion chain dominates the neutrino production in the Sun.The uncertainty of the predicted pp neutrino flux is at the sub-percent level,whereas that of the best measurement is O(10%).In this study,for the first time,we measure solar pp neutrinos in the electron recoil energy range from 24 to 144 keV using the PandaX-4T commissioning data with 0.63 tonne×year exposure.The pp neutrino flux is determined as(8.0±3.9(stat)±10.0(syst))×1010 s^(-1)cm^(-2),which is consistent with the Standard Solar Model and existing measurements,corresponding to an upper flux limit of 23.3×10^(10)s^(-1)cm^(-2)at 90%C.L..展开更多
In our published letter,[1]we have identified a minor error in Figs.2 and 3.Instead,we have 2111 events in these two plots with 646,249,382,and 834 events in Run 9(20.0 ton·day),Run 10(19.4 ton·day),Run 11–...In our published letter,[1]we have identified a minor error in Figs.2 and 3.Instead,we have 2111 events in these two plots with 646,249,382,and 834 events in Run 9(20.0 ton·day),Run 10(19.4 ton·day),Run 11–1(24.2 ton·day),and Run 11–2(37.1 ton·day).The mistake is due to an incorrect application of a small energy non-linearity(known as the BLS non-linearity)in making plots,but has no impact to the final results.Figures 2 and 3 are now updated in this note.展开更多
We report a search for new physics signals using the low energy electron recoil events in the complete data set from PandaX-Ⅱ,in light of the recent event excess reported by XENON1 T.The data correspond to a total ex...We report a search for new physics signals using the low energy electron recoil events in the complete data set from PandaX-Ⅱ,in light of the recent event excess reported by XENON1 T.The data correspond to a total exposure of 100.7 ton·day with liquid xenon.With robust estimates of the dominant background spectra,we perform sensitive searches on solar axions and neutrinos with enhanced magnetic moment.It is found that the axionelectron coupling gAe<4.6×10^(-12) for an axion mass less than 0.1 keV/c^(2) and the neutrino magnetic moment μv<4.9×10^(-11)μB at 90%confidence level.The observed excess from XENON1 T is within our experimental constraints.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
Signal reconstruction through software processing is a crucial component of the background and signal models in the PandaX-4T experiment,which is a multi-tonne dark matter direct search experiment.The accuracy of sign...Signal reconstruction through software processing is a crucial component of the background and signal models in the PandaX-4T experiment,which is a multi-tonne dark matter direct search experiment.The accuracy of signal reconstruction is influenced by various detector artifacts,including noise,dark count of photomultiplier,photoionization of impurities in the detector,and other relevant considerations.In this study,we presented a detailed description of a semi-data-driven approach designed to simulate a signal waveform.This work provides a reliable model for the efficiency and bias of the signal reconstruction in the data analysis of PandaX-4T.By comparing critical variables that relate to the temporal shape and hit pattern of the signals,we found good agreement between the simulation and data.展开更多
Self-interacting dark matter(SIDM)is a leading candidate proposed to solve discrepancies between predictions of the prevailing cold dark matter theory and observations of galaxies.Many SIDM models predict the existenc...Self-interacting dark matter(SIDM)is a leading candidate proposed to solve discrepancies between predictions of the prevailing cold dark matter theory and observations of galaxies.Many SIDM models predict the existence of a light force carrier that mediates strong dark matter self-interactions.If the mediator couples to the standard model particles,it could produce characteristic signals in dark matter direct detection experiments.We report searches for signals of SIDM models with a light mediator using the full dataset of the PandaX-II experiment,basing on a total exposure of 132 tonne-days.No significant excess over background is found,and our likelihood analysis leads to a strong upper limit on the dark matter-nucleon coupling strength.We further combine the PandaX-II constraints and those from observations of the light element abundances in the early universe,and show that direct detection and cosmological probes can provide complementary constraints on dark matter models with a light mediator.展开更多
Precise measurement of two-neutrino double beta decay(DBD)half-life is an important step for the searches of Majorana neutrinos with neutrinoless double beta decay.We report the measurement of DBD half-life of 136xe u...Precise measurement of two-neutrino double beta decay(DBD)half-life is an important step for the searches of Majorana neutrinos with neutrinoless double beta decay.We report the measurement of DBD half-life of 136xe using the Pandax-4T dual-phase Time Projection Chamber(TPC)with 3.7-tonne natural xenon and the first 94.9-day physics data release.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
In dark matter direct detection experiments,neutron is a serious source of background,which can mimic the dark matter-nucleus scattering signals.In this paper,we present an improved evaluation of the neutron backgroun...In dark matter direct detection experiments,neutron is a serious source of background,which can mimic the dark matter-nucleus scattering signals.In this paper,we present an improved evaluation of the neutron background in the PandaX-II dark matter experiment by a novel approach.Instead of fully relying on the Monte Carlo simulation,the overall neutron background is determined from the neutron-induced high energy signals in the data.In addition,the probability of producing a dark-matter-like background per neutron is evaluated with a complete Monte Carlo generator,where the correlated emission of neutron(s)andγ(s)in the(α,n)reactions and spontaneous fissions is taken into consideration.With this method,the neutron backgrounds in the Run 9(26-ton-day)and Run 10(28-ton-day)data sets of PandaX-II are estimated to be(0.66±0.24)and(0.47±0.25)events,respectively.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
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
Ⅰ.INTRODUCTION The direct detection of dark matter particles,especially the weakly interacting massive particles(WIMPs),is being actively carried out by a couple of experiments worldwide[1].In recent years,the PandaX...Ⅰ.INTRODUCTION The direct detection of dark matter particles,especially the weakly interacting massive particles(WIMPs),is being actively carried out by a couple of experiments worldwide[1].In recent years,the PandaX-Ⅱ experiment located in the China Jinping Underground Laboratory(CJPL)[1-3],which uses the technology of dual phase liquid xenon time projection chambers(TPCs),has pushed the limits of the cross section between WIMPs and nucleons to a new level for most of the possible WIMP masses;other experiments of the same type are also being performed[4–10].展开更多
Neutron-induced nuclear recoil background is critical to dark matter searches in the PandaX-4T liquid xenon experiment.In this study,we investigate the features of neutron background in liquid xenon and evaluate its c...Neutron-induced nuclear recoil background is critical to dark matter searches in the PandaX-4T liquid xenon experiment.In this study,we investigate the features of neutron background in liquid xenon and evaluate its contribution in single scattering nuclear recoil events using three methods.The first method is fully based on Monte Carlo simulations.The last two are data-driven methods that also use multiple scattering signals and high energy signals in the data.In the PandaX-4T commissioning data with an exposure of 0.63 tonne-year,all these methods give a consistent result,i.e.,there are 1.15±0.57 neutron-induced backgrounds in the dark matter signal region within an approximated nuclear recoil energy window between 5 and 100 keV.展开更多
基金supported in part by the grants from the National Science Foundation of China(12090060,12090063,12105052,12005131,11905128,11925502)the Office of Science and Technology,Shanghai Municipal Government(22JC1410100)+6 种基金the National Science Foundation of Sichuan ProvinceChina(2024NSFSC1371)the support from the Double First Class Plan of Shanghai Jiao Tong Universitythe sponsorship from the Chinese Academy of Sciences Center for Excellence in Particle Physics(CCEPP)Hongwen Foundation in Hong KongTencentNew Cornerstone Science Foundation in China。
文摘The proton-proton(pp)fusion chain dominates the neutrino production in the Sun.The uncertainty of the predicted pp neutrino flux is at the sub-percent level,whereas that of the best measurement is O(10%).In this study,for the first time,we measure solar pp neutrinos in the electron recoil energy range from 24 to 144 keV using the PandaX-4T commissioning data with 0.63 tonne×year exposure.The pp neutrino flux is determined as(8.0±3.9(stat)±10.0(syst))×1010 s^(-1)cm^(-2),which is consistent with the Standard Solar Model and existing measurements,corresponding to an upper flux limit of 23.3×10^(10)s^(-1)cm^(-2)at 90%C.L..
文摘In our published letter,[1]we have identified a minor error in Figs.2 and 3.Instead,we have 2111 events in these two plots with 646,249,382,and 834 events in Run 9(20.0 ton·day),Run 10(19.4 ton·day),Run 11–1(24.2 ton·day),and Run 11–2(37.1 ton·day).The mistake is due to an incorrect application of a small energy non-linearity(known as the BLS non-linearity)in making plots,but has no impact to the final results.Figures 2 and 3 are now updated in this note.
基金Supported in part by the National Key R&D Program of China(Grant No.2016YFA0400301)the National Natural Science Foundation of China(Grant Nos.11525522,11775141,and 11755001)+5 种基金the Double First Class Plan of the Shanghai Jiao Tong University,the China Postdoctoral Science Foundation(Grant No.2018M640036)the Office of Science and Technology,Shanghai Municipal Government(Grant Nos.11DZ2260700,16DZ2260200,and 18JC1410200)the Key Laboratory for Particle Physics,Astrophysics and Cosmology,Ministry of Education,for important supportsponsorship from the Chinese Academy of Sciences Center for Excellence in Particle Physics(CCEPP)the Hongwen Foundation in Hong Kongthe Tencent Foundation in China。
文摘We report a search for new physics signals using the low energy electron recoil events in the complete data set from PandaX-Ⅱ,in light of the recent event excess reported by XENON1 T.The data correspond to a total exposure of 100.7 ton·day with liquid xenon.With robust estimates of the dominant background spectra,we perform sensitive searches on solar axions and neutrinos with enhanced magnetic moment.It is found that the axionelectron coupling gAe<4.6×10^(-12) for an axion mass less than 0.1 keV/c^(2) and the neutrino magnetic moment μv<4.9×10^(-11)μB at 90%confidence level.The observed excess from XENON1 T is within our experimental constraints.
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 in part by the National Science Foundation of China(12090060,12090061)Ministry of Science and Technology of China(2023YFA1606200)+1 种基金Office of Science and Technology,Shanghai Municipal Government(22JC1410100)the Double First Class Plan of the Shanghai Jiao Tong University and Guangzhou Municipal Science and Technology Project(202201010991)。
文摘Signal reconstruction through software processing is a crucial component of the background and signal models in the PandaX-4T experiment,which is a multi-tonne dark matter direct search experiment.The accuracy of signal reconstruction is influenced by various detector artifacts,including noise,dark count of photomultiplier,photoionization of impurities in the detector,and other relevant considerations.In this study,we presented a detailed description of a semi-data-driven approach designed to simulate a signal waveform.This work provides a reliable model for the efficiency and bias of the signal reconstruction in the data analysis of PandaX-4T.By comparing critical variables that relate to the temporal shape and hit pattern of the signals,we found good agreement between the simulation and data.
基金This work was supported by a Double Top-class grant from Shanghai Jiao Tong University,and the National Natural Science Foundation of China(Grant No.11875190)Department of Energy(Grant No.de-sc0008541)the John Templeton Foundation(Grant No.#61884).
文摘Self-interacting dark matter(SIDM)is a leading candidate proposed to solve discrepancies between predictions of the prevailing cold dark matter theory and observations of galaxies.Many SIDM models predict the existence of a light force carrier that mediates strong dark matter self-interactions.If the mediator couples to the standard model particles,it could produce characteristic signals in dark matter direct detection experiments.We report searches for signals of SIDM models with a light mediator using the full dataset of the PandaX-II experiment,basing on a total exposure of 132 tonne-days.No significant excess over background is found,and our likelihood analysis leads to a strong upper limit on the dark matter-nucleon coupling strength.We further combine the PandaX-II constraints and those from observations of the light element abundances in the early universe,and show that direct detection and cosmological probes can provide complementary constraints on dark matter models with a light mediator.
基金This project is supported in part by grants from the Ministry of Science and Technology of China(No.2016YFA0400301 and 2016YFA0400302)grants from National Science Foundation of China(Nos.12090061,12090062,12005131,11905128,and 11925502)by Office of Science and Technology,Shanghai Municipal Government(grant No.18JC1410200).
文摘Precise measurement of two-neutrino double beta decay(DBD)half-life is an important step for the searches of Majorana neutrinos with neutrinoless double beta decay.We report the measurement of DBD half-life of 136xe using the Pandax-4T dual-phase Time Projection Chamber(TPC)with 3.7-tonne natural xenon and the first 94.9-day physics data release.
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 the Double Top-class of Shanghai Jiao Tong University,the National Natural Science Foundation of China(Grant Nos.11435008,11505112,11525522,11775141,and 11755001)the Ministry of Science and Technology of China(Grant No.2016YFA0400301)+4 种基金the Office of Science and Technology,Shanghai Municipal Government(Grant Nos.11DZ2260700,16DZ2260200,and 18JC1410200)the Key Laboratory for Particle Physics,Astrophysics and Cosmology,Ministry of Education,for important supportthe Chinese Academy of Sciences Center for Excellence in Particle Physics(CCEPP)Hongwen Foundation in Hong Kongwe thank the CJPL administration and the Yalong River Hydropower Development Company Ltd.for indispensable logistical support and other help.
文摘In dark matter direct detection experiments,neutron is a serious source of background,which can mimic the dark matter-nucleus scattering signals.In this paper,we present an improved evaluation of the neutron background in the PandaX-II dark matter experiment by a novel approach.Instead of fully relying on the Monte Carlo simulation,the overall neutron background is determined from the neutron-induced high energy signals in the data.In addition,the probability of producing a dark-matter-like background per neutron is evaluated with a complete Monte Carlo generator,where the correlated emission of neutron(s)andγ(s)in the(α,n)reactions and spontaneous fissions is taken into consideration.With this method,the neutron backgrounds in the Run 9(26-ton-day)and Run 10(28-ton-day)data sets of PandaX-II are estimated to be(0.66±0.24)and(0.47±0.25)events,respectively.
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.
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 in part by a grant from the Ministry of Science and Technology of China(2016YFA0400301)National Science Foundation of China(12090060,12005131,11905128,11925502,11775141)Office of Science and Technology,Shanghai Municipal Government(18JC1410200)。
文摘Ⅰ.INTRODUCTION The direct detection of dark matter particles,especially the weakly interacting massive particles(WIMPs),is being actively carried out by a couple of experiments worldwide[1].In recent years,the PandaX-Ⅱ experiment located in the China Jinping Underground Laboratory(CJPL)[1-3],which uses the technology of dual phase liquid xenon time projection chambers(TPCs),has pushed the limits of the cross section between WIMPs and nucleons to a new level for most of the possible WIMP masses;other experiments of the same type are also being performed[4–10].
基金Supported in part by grants from National Science Foundation of China(12090061,12005131,11905128,11925502)the Ministry of Science and Technology of China(2016YFA0400301)the Office of Science and Technology,Shanghai Municipal Government(18JC1410200)。
文摘Neutron-induced nuclear recoil background is critical to dark matter searches in the PandaX-4T liquid xenon experiment.In this study,we investigate the features of neutron background in liquid xenon and evaluate its contribution in single scattering nuclear recoil events using three methods.The first method is fully based on Monte Carlo simulations.The last two are data-driven methods that also use multiple scattering signals and high energy signals in the data.In the PandaX-4T commissioning data with an exposure of 0.63 tonne-year,all these methods give a consistent result,i.e.,there are 1.15±0.57 neutron-induced backgrounds in the dark matter signal region within an approximated nuclear recoil energy window between 5 and 100 keV.
