The Jiangmen Underground Neutrino Observatory(JUNO)started physics data taking on 26 August 2025.JUNO consists of a 20-kton liquid scintillator central detector,surrounded by a 35 kton water pool serving as a Cherenko...The Jiangmen Underground Neutrino Observatory(JUNO)started physics data taking on 26 August 2025.JUNO consists of a 20-kton liquid scintillator central detector,surrounded by a 35 kton water pool serving as a Cherenkov veto,and almost 1000 m2 of plastic scintillator veto on top.The detector is located in a shallow underground laboratory with an overburden of 1800 m.w.e.This paper presents the performance results of the detector,extensively studied during the commissioning of the water phase,the subsequent liquid scintillator filling phase,and the first physics runs.The liquid scintillator achieved an attenuation length of 20.6 m at 430 nm,while the high coverage PMT system and scintillator together yielded about 1785 photoelectrons per MeV of energy deposit at the detector centre,measured using the 2.223 MeVγfrom neutron captures on hydrogen with an Am-C calibration source.The reconstructed energy resolution is 3.4%for two 0.511 MeVγat the detector centre and 2.9%for the 0.93 MeV quenched 214Po alpha decays from natural radioactive sources.The energy non-linearity is calibrated to better than 1%.Intrinsic contaminations of 238U and 232Th in the liquid scintillator are below 10-16 g/g,assuming secular equilibrium.The water Cherenkov detector achieves a muon detection efficiency better than 99.9%for muons traversing the liquid scintillator volume.During the initial science runs,the data acquisition duty cycle exceeded 97.8%,demonstrating the excellent stability and readiness of JUNO for high-precision neutrino physics.展开更多
This paper presents an energy resolution study of the JUNO experiment,incorporating the latest knowledge acquired during the detector construction phase.The determination of neutrino mass ordering in JUNO requires an ...This paper presents an energy resolution study of the JUNO experiment,incorporating the latest knowledge acquired during the detector construction phase.The determination of neutrino mass ordering in JUNO requires an exceptional energy resolution better than 3% at 1 MeV.To achieve this ambitious goal,significant efforts have been undertaken in the design and production of the key components of the JUNO detector.Various factors affecting the detection of inverse beta decay signals have an impact on the energy resolution,extending beyond the statistical fluctuations of the detected number of photons,such as the properties of the liquid scintillator,performance of photomultiplier tubes,and the energy reconstruction algorithm.To account for these effects,a full JUNO simulation and reconstruction approach is employed.This enables the modeling of all relevant effects and the evaluation of associated inputs to accurately estimate the energy resolution.The results of this study reveal an energy resolution of 2.95% at 1 Mev.Furthermore,this study assesses the contribution of major effects to the overall energy resolution budget.This analysis serves as a reference for interpreting future measurements of energy resolution during JUNO data collection.Moreover,it provides a guideline for comprehending the energy resolution characteristics of liquid scintillator-based detectors.展开更多
摘要The Jiangmen Underground Neutrino Observatory(JUNO)started physics data taking on 26 August 2025.JUNO consists of a 20-kton liquid scintillator central detector,surrounded by a 35 kton water pool serving as a Cherenkov veto,and almost 1000 m2 of plastic scintillator veto on top.The detector is located in a shallow underground laboratory with an overburden of 1800 m.w.e.This paper presents the performance results of the detector,extensively studied during the commissioning of the water phase,the subsequent liquid scintillator filling phase,and the first physics runs.The liquid scintillator achieved an attenuation length of 20.6 m at 430 nm,while the high coverage PMT system and scintillator together yielded about 1785 photoelectrons per MeV of energy deposit at the detector centre,measured using the 2.223 MeVγfrom neutron captures on hydrogen with an Am-C calibration source.The reconstructed energy resolution is 3.4%for two 0.511 MeVγat the detector centre and 2.9%for the 0.93 MeV quenched 214Po alpha decays from natural radioactive sources.The energy non-linearity is calibrated to better than 1%.Intrinsic contaminations of 238U and 232Th in the liquid scintillator are below 10-16 g/g,assuming secular equilibrium.The water Cherenkov detector achieves a muon detection efficiency better than 99.9%for muons traversing the liquid scintillator volume.During the initial science runs,the data acquisition duty cycle exceeded 97.8%,demonstrating the excellent stability and readiness of JUNO for high-precision neutrino physics.
基金Supported by the Chinese Academy of Sciencesthe National Key R&D Program of China+20 种基金the CAS Center for Excellence in Particle Physics,Wuyi Universitythe Tsung-Dao Lee Institute of Shanghai Jiao Tong University in Chinathe Institut National de Physique Nucléaire et de Physique de Particules(IN2P3)in Francethe Istituto Nazionale di Fisica Nucleare(INFN)in Italythe Italian-Chinese collaborative research program MAECI-NSFCthe Fond de la Recherche Scientifique(F.R.S-FNRS)FWO under the"Excellence of Science-EOS"in Belgiumthe Conselho Nacional de Desenvolvimento Científico e Tecnològico in Brazilthe Agencia Nacional de Investigacion y Desarrollo and ANID Millennium Science Initiative Program—ICN2019_044 in Chilethe Charles University Research Centre and the Ministry of Education,Youth,and Sports in Czech Republicthe Deutsche Forschungsgemeinschaft(DFG)the Helmholtz Associationthe Cluster of Excellence PRISMA+in Germanythe Joint Institute of Nuclear Research(JINR)Lomonosov Moscow State University in Russiathe joint Russian Science Foundation(RSF)National Natural Science Foundation of China(NSFC)research programthe MOST and MOE in Taiwan,Chinathe Chulalongkorn University and Suranaree University of Technology in Thailandthe University of California at Irvinethe National Science Foundation in USA。
摘要This paper presents an energy resolution study of the JUNO experiment,incorporating the latest knowledge acquired during the detector construction phase.The determination of neutrino mass ordering in JUNO requires an exceptional energy resolution better than 3% at 1 MeV.To achieve this ambitious goal,significant efforts have been undertaken in the design and production of the key components of the JUNO detector.Various factors affecting the detection of inverse beta decay signals have an impact on the energy resolution,extending beyond the statistical fluctuations of the detected number of photons,such as the properties of the liquid scintillator,performance of photomultiplier tubes,and the energy reconstruction algorithm.To account for these effects,a full JUNO simulation and reconstruction approach is employed.This enables the modeling of all relevant effects and the evaluation of associated inputs to accurately estimate the energy resolution.The results of this study reveal an energy resolution of 2.95% at 1 Mev.Furthermore,this study assesses the contribution of major effects to the overall energy resolution budget.This analysis serves as a reference for interpreting future measurements of energy resolution during JUNO data collection.Moreover,it provides a guideline for comprehending the energy resolution characteristics of liquid scintillator-based detectors.