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
The Jiangmen Underground Neutrino Observatory(JUNO)features a 20 kt multi-purpose underground liquid scintillator sphere as its main detector.Some of JUNO's features make it an excellent location for^8B solar neut...The Jiangmen Underground Neutrino Observatory(JUNO)features a 20 kt multi-purpose underground liquid scintillator sphere as its main detector.Some of JUNO's features make it an excellent location for^8B solar neutrino measurements,such as its low-energy threshold,high energy resolution compared with water Cherenkov detectors,and much larger target mass compared with previous liquid scintillator detectors.In this paper,we present a comprehensive assessment of JUNO's potential for detecting^8B solar neutrinos via the neutrino-electron elastic scattering process.A reduced 2 MeV threshold for the recoil electron energy is found to be achievable,assuming that the intrinsic radioactive background238U and232Th in the liquid scintillator can be controlled to 10-17g/g.With ten years of data acquisition,approximately 60,000 signal and 30,000 background events are expected.This large sample will enable an examination of the distortion of the recoil electron spectrum that is dominated by the neutrino flavor transformation in the dense solar matter,which will shed new light on the inconsistency between the measured electron spectra and the predictions of the standard three-flavor neutrino oscillation framework.IfDelta m221=4.8times10-5;(7.5times10-5)eV2,JUNO can provide evidence of neutrino oscillation in the Earth at approximately the 3sigma(2sigma)level by measuring the non-zero signal rate variation with respect to the solar zenith angle.Moreover,JUNO can simultaneously measureDelta m^221using^8B solar neutrinos to a precision of 20%or better,depending on the central value,and to sub-percent precision using reactor antineutrinos.A comparison of these two measurements from the same detector will help understand the current mild inconsistency between the value of Delta m^221reported by solar neutrino experiments and the KamLAND experiment.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 Sciences,the National Key R&D Program of Chinathe CAS Center for Excellence in Particle Physics+13 种基金the Joint Large Scale Scientific Facility Funds of the NSFC and CASWuyi University,and the Tsung-Dao Lee Instiute of Shanghai Jiao Tong University in Chinathe In stiut National de Physique Nucleaire et de Physique de Particules(IN2P3)in Francethe Istituto Nazionale di Fisica Nucleare(INFN)in Italythe Fond de la Recherche Scintifique(F.R.S-FNRS)and FWO under the"Excellence of Science-EOS"in Belgiumthe Conselho Nacional de Desenvolvimento Cientificoce Tecnologico in Brazilthe Agencia Nacional de Investigacion y Desrrollo in Chilethe Charles University Research Centre and the Ministry of Education,Youth,and Sports in Czech Republicthe Deutsche Forschungsgemeinschaft(DFG),the Helmholtz Association,and the Cluster of Exellence PRISMA+in Germanythe Joint Institute of Nuclear Research(JINR),Lomonosov Moscow State University,and Russian Foundation for Basic Research(RFBR)in Russiathe MOST and MOE in Taiwanthe Chu-lalongkorm University and Suranaree University of Technology in Thailandthe University of aliformia at Irvine in USA.
摘要The Jiangmen Underground Neutrino Observatory(JUNO)features a 20 kt multi-purpose underground liquid scintillator sphere as its main detector.Some of JUNO's features make it an excellent location for^8B solar neutrino measurements,such as its low-energy threshold,high energy resolution compared with water Cherenkov detectors,and much larger target mass compared with previous liquid scintillator detectors.In this paper,we present a comprehensive assessment of JUNO's potential for detecting^8B solar neutrinos via the neutrino-electron elastic scattering process.A reduced 2 MeV threshold for the recoil electron energy is found to be achievable,assuming that the intrinsic radioactive background238U and232Th in the liquid scintillator can be controlled to 10-17g/g.With ten years of data acquisition,approximately 60,000 signal and 30,000 background events are expected.This large sample will enable an examination of the distortion of the recoil electron spectrum that is dominated by the neutrino flavor transformation in the dense solar matter,which will shed new light on the inconsistency between the measured electron spectra and the predictions of the standard three-flavor neutrino oscillation framework.IfDelta m221=4.8times10-5;(7.5times10-5)eV2,JUNO can provide evidence of neutrino oscillation in the Earth at approximately the 3sigma(2sigma)level by measuring the non-zero signal rate variation with respect to the solar zenith angle.Moreover,JUNO can simultaneously measureDelta m^221using^8B solar neutrinos to a precision of 20%or better,depending on the central value,and to sub-percent precision using reactor antineutrinos.A comparison of these two measurements from the same detector will help understand the current mild inconsistency between the value of Delta m^221reported by solar neutrino experiments and the KamLAND experiment.