摘要
In the past few decades,numerous searches have been made for the neutrinoless double-beta decay（0νββ） process,aiming to establish whether neutrinos are their own antiparticles（Majorana neutrinos）,but no 0νββdecay signal has yet been observed.A number of new experiments are proposed but they ultimately suffer from a common problem： the sensitivity may not increase indefinitely with the target mass.We have performed a detailed analysis of the physics potential by using the Jiangmen Underground Neutrino Observatory（JUNO） to improve the sensitivity to 0νββ up to a few me V,a major step forward with respect to the experiments currently being planned.JUNO is a 20 kton low-background liquid scintillator（LS） detector with 3%/（E（MeV））1/2 energy resolution,now under construction.It is feasible to build a balloon filled with enriched xenon gas（with136Xe up to 80%） dissolved in LS,inserted into the central region of the JUNO LS.The energy resolution is 1.9% at the Q-value of 136Xe 0νββ decay.Ultra-low background is the key for 0νββ decay searches.Detailed studies of background rates from intrinsic 2νββ and 8B solar neutrinos,natural radioactivity,and cosmogenic radionuclides（including light isotopes and 137Xe） were performed and several muon veto schemes were developed.We find that JUNO has the potential to reach a sensitivity（at 90% C.L.） to T1/20νββof 1.8×1028yr（5.6×1027yr） with 50 tons（5 tons） of fiducial136 Xe and 5 years exposure,while in the 50-ton case the corresponding sensitivity to the effective neutrino mass,mββ,could reach（5–12） meV,covering completely the allowed region of inverted neutrino mass ordering.
In the past few decades,numerous searches have been made for the neutrinoless double-beta decay（0νββ） process,aiming to establish whether neutrinos are their own antiparticles（Majorana neutrinos）,but no 0νββdecay signal has yet been observed.A number of new experiments are proposed but they ultimately suffer from a common problem： the sensitivity may not increase indefinitely with the target mass.We have performed a detailed analysis of the physics potential by using the Jiangmen Underground Neutrino Observatory（JUNO） to improve the sensitivity to 0νββ up to a few me V,a major step forward with respect to the experiments currently being planned.JUNO is a 20 kton low-background liquid scintillator（LS） detector with 3%/（E（MeV））1/2 energy resolution,now under construction.It is feasible to build a balloon filled with enriched xenon gas（with136Xe up to 80%） dissolved in LS,inserted into the central region of the JUNO LS.The energy resolution is 1.9% at the Q-value of 136Xe 0νββ decay.Ultra-low background is the key for 0νββ decay searches.Detailed studies of background rates from intrinsic 2νββ and 8B solar neutrinos,natural radioactivity,and cosmogenic radionuclides（including light isotopes and 137Xe） were performed and several muon veto schemes were developed.We find that JUNO has the potential to reach a sensitivity（at 90% C.L.） to T1/20νββof 1.8×1028yr（5.6×1027yr） with 50 tons（5 tons） of fiducial136 Xe and 5 years exposure,while in the 50-ton case the corresponding sensitivity to the effective neutrino mass,mββ,could reach（5–12） meV,covering completely the allowed region of inverted neutrino mass ordering.
基金
Supported by Strategic Priority Research Program of Chinese Academy of Sciences(XDA10010900)
CAS Center for Excellence in Particle Physics(CCEPP)
Postdoctoral Science Foundation of China and Chinese Academy of Sciences(2015IHEPBSH101)
Program of International S&T Cooperation of Mo ST(2015DFG02000)
