Considering a new type of environment influences, we use a two-energy-level quantum system to investigate neutrino oscillations in medium. Besides the matter effects derived by Wolfenstein, there may exist extra term...Considering a new type of environment influences, we use a two-energy-level quantum system to investigate neutrino oscillations in medium. Besides the matter effects derived by Wolfenstein, there may exist extra terms due to a unitary evolution of the system between pure and mixed states, so the evolution equation is modified obviously. We show that the extra terms may play some role and induce observable effects in solar neutrino problem, especially, in the long baseline neutrino oscillation experiments which are under serious consideration recently, if the parameters fall into a suitable region.展开更多
We report an improved measurement of the neutrino mixing angle θ13 from the Daya Bay Reactor Neutrino Experiment. We exclude a zero value for sin22θ13 with a significance of 7.7 standard deviations. Electron antineu...We report an improved measurement of the neutrino mixing angle θ13 from the Daya Bay Reactor Neutrino Experiment. We exclude a zero value for sin22θ13 with a significance of 7.7 standard deviations. Electron antineutrinos from six reactors of 2.9 GWm th were detected in six antineutrino detectors deployed in two near （flux-weighted baselines of 470 m and 576 m） and one far （1648 m） underground experimental halls. Using 139 days of data, 28909 （205308） electron antineutrino candidates were detected at the far hall （near halls）. The ratio of the observed to the expected number of antineutrinos assuming no oscillations at the far hall is 0.944± 0.007（stat.） ± 0.003（syst.）. An analysis of the relative rates in six detectors finds sin22θ13=0.089± 0.010（stat.）±0.005（syst.） in a three-neutrino framework.展开更多
Neutrinos are elementary particles in the Standard Model. Neutrino oscillation is a quantum mechanical phenomenon beyond the Standard Model. Neutrino oscillation can be described by two independent mass-squared differ...Neutrinos are elementary particles in the Standard Model. Neutrino oscillation is a quantum mechanical phenomenon beyond the Standard Model. Neutrino oscillation can be described by two independent mass-squared differences △m21^2, △m31^2 （or △m32^2） and a 3× 3 unitary matrix, containing three mixing angles θ12, θ23, θ13, and one charge-parity （CP） phase. θ12 is about 34° and determined by solar neutrino experiments and the reactor neutrino experiment KamLAND. θ23 is about 45° and determined by atmospheric neutrino experiments and accelerator neutrino experiments. 013 can be measured by either accelerator or reactor neutrino experiments. On Mar. 8, 2012, the Daya Bay Reactor Neutrino Experiment reported the first observation of non-zero 013 with 5.2 standard deviations. In June, with 2.5× previous data, Daya Bay improved the measurement of sin2 2013 = 0.089 ± 0.010（stat）± 0.005（syst）.展开更多
The antineutrino detectors for the Daya Bay reactor neutrino experiment are liquid scintillator detectors designed to detect electron anti-neutrino via inverse beta interactions with high efficiency and low background...The antineutrino detectors for the Daya Bay reactor neutrino experiment are liquid scintillator detectors designed to detect electron anti-neutrino via inverse beta interactions with high efficiency and low backgrounds.Since the antineutrino detector will be installed and immerged in water Cherenkov detector and will run for 3 to 5 years,water tightness is critical to the successful operation of the antineutrino detectors.A special seal technique was used for this purpose.Three leak checking methods have been employed to ensure the seal quality.This paper describes the sealing method and leakage testing results.展开更多
Subject to neutrino experiments, the mixing matrix of ordinary neutrinos can still have small vi-olation from unitarity. We introduce a quasi-unitary matrix to interpret this violation and propose a natural scheme to ...Subject to neutrino experiments, the mixing matrix of ordinary neutrinos can still have small vi-olation from unitarity. We introduce a quasi-unitary matrix to interpret this violation and propose a natural scheme to parameterize it. A quasi-unitary factor △QF is defined to be measured in neutrino oscillation exper-iments and the numerical results show that the improvement in experimental precision may help us figure out the secret of neutrino mixing.展开更多
Resistive Plate Chamber （RPC） modules will be used as one part of the cosmic muon veto system in the Daya Bay reactor neutrino experiment. A total of 189 RPC modules will cover the three water pools in the experimen...Resistive Plate Chamber （RPC） modules will be used as one part of the cosmic muon veto system in the Daya Bay reactor neutrino experiment. A total of 189 RPC modules will cover the three water pools in the experiment. To achieve track reconstruction and high efficiency, each module consists of 4 layers, each of which contains two sizes of bare chambers. The placement of bare chambers is reversed in different layers to reduce the overlapping dead areas. The module efficiency and patch emciency were studied both in simulation and test of the data analysis. 143 modules have been constructed and tested. The preliminary study shows that the module and patch 3 out of 4 layers efficiency reaches about 98%.展开更多
Updated May 2014 by K. Nakamura （Kavli IPMU （WPI）, U. Tokyo, KEK）, and S.T. Petcov （SISSA/INFN Trieste, Kavli IPMU （WPI）, U. Tokyo, Bulgarian Academy of Sciences）.
We investigate prospects of building a future accelerator-based neutrino oscillation experiment in China,including site selection,beam optimization and tau neutrino physics aspects.CP violation,non-unitary mixing and ...We investigate prospects of building a future accelerator-based neutrino oscillation experiment in China,including site selection,beam optimization and tau neutrino physics aspects.CP violation,non-unitary mixing and non-standard neutrino interactions are discussed.We simulate neutrino beam setups based on muon and beta decay techniques and compare Chinese laboratory sites by their expected sensitivities.A case study on the Super Proton-Proton Collider and the China JinPing Laboratory is also presented.It is shown that the muon-decay-based beam setup can measure the Dirac CP phase by about 14.2°precision at 1σCL,whereas non-unitarity can be probed down to |α_(ij)|≲0.37(i≠j=1,2,3)and non-standard interactions to|ϵ_(ℓℓ′)^(m)|≲0.11(ℓ≠ℓ′=e,μ,τ)at 90% CL,respectively.展开更多
A summary of the current status of neutrino oscillations is given. We also include a brief description of the earlier development of neutrino physics and illustrate the roles that neutrinos play in several areas other...A summary of the current status of neutrino oscillations is given. We also include a brief description of the earlier development of neutrino physics and illustrate the roles that neutrinos play in several areas other than particle physics.展开更多
In this paper, we first discuss the detection of supernova neutrinos on earth. Then we propose a possible method to acquire information about θ13 smaller than 1.5° by detecting the ratio of the event numbers of ...In this paper, we first discuss the detection of supernova neutrinos on earth. Then we propose a possible method to acquire information about θ13 smaller than 1.5° by detecting the ratio of the event numbers of different flavor supernova neutrinos. Such an sensitivity cannot yet be achieved by the Daya Bay reactor neutrino experiment.展开更多
Supernova （SN） neutrinos detected on the Earth are subject to the shock wave effects, the Mikheyev- Smirnov-Wolfenstein （MSW） effects, the neutrino collective effects and the Earth matter effects. Considering the ...Supernova （SN） neutrinos detected on the Earth are subject to the shock wave effects, the Mikheyev- Smirnov-Wolfenstein （MSW） effects, the neutrino collective effects and the Earth matter effects. Considering the recent experimental result about the large mixing angle 013 （-8.8°） provided by the Daya Bay Collaboration and applying the available knowledge for the neutrino conversion probability in the high resonance region of SN, PH , which is in the form of hypergeometric function in the case of large 813, we deduce the expression of PH taking into account the shock wave effects. It is found that PH is not zero in a certain range of time due to the shock wave effects. After considering all the four physical effects and scanning relevant parameters, we calculate the event numbers of SN neutrinos for the ＂Garehing＂ distribution of neutrino energy spectrum. From the numerical results, it is found that the behaviors of neutrino event numbers detected on the Earth depend on the neutrino mass hierarchy and neutrino spectrum parameters including the dimensionless pinching parameter βa （where a refers to neutrino flavor）, the average energy 〈Ea〉, and the SN neutrino luminosities La. Finally, we give the ranges of SN neutrino event numbers that will be detected at the Daya Bay experiment.展开更多
We give an alternative description of the data produced in the KamLAND experiment, assuming the existence of a natural nuclear reactor on the boundary of the liquid and solid phases of the Earth core. Analyzing the un...We give an alternative description of the data produced in the KamLAND experiment, assuming the existence of a natural nuclear reactor on the boundary of the liquid and solid phases of the Earth core. Analyzing the uncertainty of antineutrino spectrum of georeactor origin, we show that the theoretical (which takes into account the soliton-like nuclear georeactor) total reactor antineutrino spectra describe with good accuracy the experimental KamLAND-data over the years of 2002-2007 and 2002-2009, respectively. At the same time, the parameters of mixing (△m221=2.5×10-5 eV2, tan2θ12=0.437) calculated within the framework of georeactor hypothesis substantially differ from the parameters of mixing ((△m221=7.49×10-5 eV2, tan2θ12=0.436) obtained in KamLAND-experiment for total exposure over the period of 2002-2009. By triangulation of KamLAND and Borexino data we have constructed the coordinate location of soliton-like nuclear georeactors on the boundary of the liquid and solid phases of the Earth core.展开更多
文摘Considering a new type of environment influences, we use a two-energy-level quantum system to investigate neutrino oscillations in medium. Besides the matter effects derived by Wolfenstein, there may exist extra terms due to a unitary evolution of the system between pure and mixed states, so the evolution equation is modified obviously. We show that the extra terms may play some role and induce observable effects in solar neutrino problem, especially, in the long baseline neutrino oscillation experiments which are under serious consideration recently, if the parameters fall into a suitable region.
基金Supported by the Ministry of Science and Technology of Chinathe United States Department of Energy+15 种基金the Chinese Academy of Sciencesthe National Natural Science Foundation of Chinathe Guangdong provincial governmentthe Shenzhen municipal governmentthe China Guangdong Nuclear Power GroupShanghai Laboratory for Particle Physics and Cosmologythe Research Grants Council of the Hong Kong Special Administrative Region of ChinaUniversity Development Fund of The University of Hong Kongthe MOE program for Research of Excellence at NTU, NCTUNSC fund support from Taipeithe U.S. National Science Foundationthe Alfred P. Sloan Foundationthe Ministry of EducationYouth and Sports of the Czech Republicthe Czech Science Foundationthe Joint Institute of Nuclear Research in Dubna,Russia
文摘We report an improved measurement of the neutrino mixing angle θ13 from the Daya Bay Reactor Neutrino Experiment. We exclude a zero value for sin22θ13 with a significance of 7.7 standard deviations. Electron antineutrinos from six reactors of 2.9 GWm th were detected in six antineutrino detectors deployed in two near （flux-weighted baselines of 470 m and 576 m） and one far （1648 m） underground experimental halls. Using 139 days of data, 28909 （205308） electron antineutrino candidates were detected at the far hall （near halls）. The ratio of the observed to the expected number of antineutrinos assuming no oscillations at the far hall is 0.944± 0.007（stat.） ± 0.003（syst.）. An analysis of the relative rates in six detectors finds sin22θ13=0.089± 0.010（stat.）±0.005（syst.） in a three-neutrino framework.
基金Acknowledgements The work was supported by the National Natural Science Foundation of China （Grant No. Y2118M005C）. I would like to acknowledge the Daya Bay collaborators for useful comments, especially Prof. Jun Cao and Dr. Yufeng Li who helped me a lot to improve this article.
文摘Neutrinos are elementary particles in the Standard Model. Neutrino oscillation is a quantum mechanical phenomenon beyond the Standard Model. Neutrino oscillation can be described by two independent mass-squared differences △m21^2, △m31^2 （or △m32^2） and a 3× 3 unitary matrix, containing three mixing angles θ12, θ23, θ13, and one charge-parity （CP） phase. θ12 is about 34° and determined by solar neutrino experiments and the reactor neutrino experiment KamLAND. θ23 is about 45° and determined by atmospheric neutrino experiments and accelerator neutrino experiments. 013 can be measured by either accelerator or reactor neutrino experiments. On Mar. 8, 2012, the Daya Bay Reactor Neutrino Experiment reported the first observation of non-zero 013 with 5.2 standard deviations. In June, with 2.5× previous data, Daya Bay improved the measurement of sin2 2013 = 0.089 ± 0.010（stat）± 0.005（syst）.
基金supported by the Ministry of Science and Technology of the People's Republic of China (Grant No. 2006CB808102)
文摘The antineutrino detectors for the Daya Bay reactor neutrino experiment are liquid scintillator detectors designed to detect electron anti-neutrino via inverse beta interactions with high efficiency and low backgrounds.Since the antineutrino detector will be installed and immerged in water Cherenkov detector and will run for 3 to 5 years,water tightness is critical to the successful operation of the antineutrino detectors.A special seal technique was used for this purpose.Three leak checking methods have been employed to ensure the seal quality.This paper describes the sealing method and leakage testing results.
基金Supported by National Natural Science Foundation of China (10875009)Natural Science Foundation of Beijing (1072001)China Postdoctoral Science Foundation
文摘Subject to neutrino experiments, the mixing matrix of ordinary neutrinos can still have small vi-olation from unitarity. We introduce a quasi-unitary matrix to interpret this violation and propose a natural scheme to parameterize it. A quasi-unitary factor △QF is defined to be measured in neutrino oscillation exper-iments and the numerical results show that the improvement in experimental precision may help us figure out the secret of neutrino mixing.
基金Supported by Ministry of Science and Technology of People’s Republic of China (2006CB808102)United States Department of Energy,Projects MSM0021620859 and ME08076 of Ministry of EducationYouth and Sports of Czech Republic and 202/08/0760 of Czech Science Foundation
文摘Resistive Plate Chamber （RPC） modules will be used as one part of the cosmic muon veto system in the Daya Bay reactor neutrino experiment. A total of 189 RPC modules will cover the three water pools in the experiment. To achieve track reconstruction and high efficiency, each module consists of 4 layers, each of which contains two sizes of bare chambers. The placement of bare chambers is reversed in different layers to reduce the overlapping dead areas. The module efficiency and patch emciency were studied both in simulation and test of the data analysis. 143 modules have been constructed and tested. The preliminary study shows that the module and patch 3 out of 4 layers efficiency reaches about 98%.
文摘Updated May 2014 by K. Nakamura （Kavli IPMU （WPI）, U. Tokyo, KEK）, and S.T. Petcov （SISSA/INFN Trieste, Kavli IPMU （WPI）, U. Tokyo, Bulgarian Academy of Sciences）.
基金supported in part by National Natural Science Foundation of China under Grant No.12075326 and No.11881240247by Guangdong Basic and Applied Basic Research Foundation under Grant No.2019A1515012216+1 种基金supported by China Postdoctoral Science Foundation under Grant No.2020M672930the support from the CAS Center for Excellence in Particle Physics(CCEPP)。
文摘We investigate prospects of building a future accelerator-based neutrino oscillation experiment in China,including site selection,beam optimization and tau neutrino physics aspects.CP violation,non-unitary mixing and non-standard neutrino interactions are discussed.We simulate neutrino beam setups based on muon and beta decay techniques and compare Chinese laboratory sites by their expected sensitivities.A case study on the Super Proton-Proton Collider and the China JinPing Laboratory is also presented.It is shown that the muon-decay-based beam setup can measure the Dirac CP phase by about 14.2°precision at 1σCL,whereas non-unitarity can be probed down to |α_(ij)|≲0.37(i≠j=1,2,3)and non-standard interactions to|ϵ_(ℓℓ′)^(m)|≲0.11(ℓ≠ℓ′=e,μ,τ)at 90% CL,respectively.
文摘A summary of the current status of neutrino oscillations is given. We also include a brief description of the earlier development of neutrino physics and illustrate the roles that neutrinos play in several areas other than particle physics.
基金Supported by National Natural Science Foundation of China (10535050,10675022)Key Project of Chinese Ministry of Education (106024)Special Grants from Beijing Normal University
文摘In this paper, we first discuss the detection of supernova neutrinos on earth. Then we propose a possible method to acquire information about θ13 smaller than 1.5° by detecting the ratio of the event numbers of different flavor supernova neutrinos. Such an sensitivity cannot yet be achieved by the Daya Bay reactor neutrino experiment.
基金Supported by the National Natural Science Foundation of China under Grant Nos.10975018,11175020,11275025,and 11205185the Fundamental Research Funds for the Central Universities in China
文摘Supernova （SN） neutrinos detected on the Earth are subject to the shock wave effects, the Mikheyev- Smirnov-Wolfenstein （MSW） effects, the neutrino collective effects and the Earth matter effects. Considering the recent experimental result about the large mixing angle 013 （-8.8°） provided by the Daya Bay Collaboration and applying the available knowledge for the neutrino conversion probability in the high resonance region of SN, PH , which is in the form of hypergeometric function in the case of large 813, we deduce the expression of PH taking into account the shock wave effects. It is found that PH is not zero in a certain range of time due to the shock wave effects. After considering all the four physical effects and scanning relevant parameters, we calculate the event numbers of SN neutrinos for the ＂Garehing＂ distribution of neutrino energy spectrum. From the numerical results, it is found that the behaviors of neutrino event numbers detected on the Earth depend on the neutrino mass hierarchy and neutrino spectrum parameters including the dimensionless pinching parameter βa （where a refers to neutrino flavor）, the average energy 〈Ea〉, and the SN neutrino luminosities La. Finally, we give the ranges of SN neutrino event numbers that will be detected at the Daya Bay experiment.
文摘We give an alternative description of the data produced in the KamLAND experiment, assuming the existence of a natural nuclear reactor on the boundary of the liquid and solid phases of the Earth core. Analyzing the uncertainty of antineutrino spectrum of georeactor origin, we show that the theoretical (which takes into account the soliton-like nuclear georeactor) total reactor antineutrino spectra describe with good accuracy the experimental KamLAND-data over the years of 2002-2007 and 2002-2009, respectively. At the same time, the parameters of mixing (△m221=2.5×10-5 eV2, tan2θ12=0.437) calculated within the framework of georeactor hypothesis substantially differ from the parameters of mixing ((△m221=7.49×10-5 eV2, tan2θ12=0.436) obtained in KamLAND-experiment for total exposure over the period of 2002-2009. By triangulation of KamLAND and Borexino data we have constructed the coordinate location of soliton-like nuclear georeactors on the boundary of the liquid and solid phases of the Earth core.
