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
Stainless steels have received wide attention as a substitute material for bipolar plates in high temperature proton exchange membrane fuel cell(HT-PEMFC).In the present work,the CrN,CrAlN and multilayer CrN/CrAlN coa...Stainless steels have received wide attention as a substitute material for bipolar plates in high temperature proton exchange membrane fuel cell(HT-PEMFC).In the present work,the CrN,CrAlN and multilayer CrN/CrAlN coatings were deposited on 316 L SS to increase the corrosion resistance and decrease the interfacial contact resistance.The deposited coatings exhibited face centered cubic phase structure and it was verified from the X-ray diffraction pattern.X-ray photo electron spectroscopy results showed the formation of both CrN and CrAlN layers on 316 L SS.CrN/CrAlN coating is more helpful in water management due to low surface roughness and high contact angle in the HT-PEMFC environment.The corrosion resistance behavior of all the samples were studied in 85%H_(3)PO_(4)solution at 140℃purged with H_(2)(HT-PEMFC anode)and O_(2)(HT-PEMFC cathode)gases.The results showed that all the coatings considerably improved the performance of 316 L SS and superior corrosion resistance was observed for CrN/CrAlN multilayer coating,whose protective efficiency was 98.12%and 96.14%in the two simulated HT-PEMFC environments.The results of electrochemical impedance spectroscopic studies demonstrated higher impedance for CrN/CrAlN coating.Surface morphological studies performed after corrosion studies revealed that protection ability of CrN/CrAlN coating still remained acceptable.A very low interfacial contact resistance value of 6 mΩ cm^(2) at 140 N/cm;was observed for CrN/CrAlN coating.Moreover,after corrosion studies,the interfacial contact resistance value of CrN/CrAlN coated 316 L was much lower than that of CrN and CrAlN coatings due to the increased oxidation resistance.The maximum power density of about 0.93 W/cm^(2) at 2 A/cm^(2) and output voltage of 0.96 V was observed for CrN/CrAlN coating.展开更多
The establishment of a possible connection between neutrino emission and gravitational-wave(GW)bursts is important to our understanding of the physical processes that occur when black holes or neutron stars merge.In t...The establishment of a possible connection between neutrino emission and gravitational-wave(GW)bursts is important to our understanding of the physical processes that occur when black holes or neutron stars merge.In the Daya Bay experiment,using the data collected from December 2011 to August 2017,a search was per-formed for electron-antineutrino signals that coincided with detected GW events,including GW150914,GW151012,GW151226,GW170104,GW170608,GW 170814,and GW 170817.We used three time windows of±10,±500,and±1000 s relative to the occurrence of the GW events and a neutrino energy range of 1.8 to 100 MeV to search for correlated neutrino candidates.The detected electron-antineutrino candidates were consistent with the expected background rates for all the three time windows.Assuming monochromatic spectra,we found upper limits(90%confidence level)of the electron-antineutrino fluence of(1.13-2.44)×10^(11)cm^(-2)at 5 MeV to 8.0×10^(7)cm^(-2)at 100 MeV for the three time w indows.Under the assumption of a Fermi-Dirac spectrum,the upper limits were found to be(5.4-7.0)×10^(9)cm^(2)for the three time windows.展开更多
The prediction of reactor antineutrino spectra will play a crucial role as reactor experiments enter the precision era.The positron energy spectrum of 3.5 million antineutrino inverse beta decay reactions observed by ...The prediction of reactor antineutrino spectra will play a crucial role as reactor experiments enter the precision era.The positron energy spectrum of 3.5 million antineutrino inverse beta decay reactions observed by the Daya Bay experiment,in combination with the fission rates of fissile isotopes in the reactor,is used to extract the positron energy spectra resulting from the fission of specific isotopes.This information can be used to produce a precise,data-based prediction of the antineutrino energy spectrum in other reactor antineutrino experiments with different fission fractions than Daya Bay.The positron energy spectra are unfolded to obtain the antineutrino energy spectra by removing the contribution from detector response with the Wiener-SVD unfolding method.Consistent results are obtained with other unfolding methods.A technique to construct a data-based prediction of the reactor antineutrino energy spectrum is proposed and investigated.Given the reactor fission fractions,the technique can predict the energy spectrum to a 2%precision.In addition,we illustrate how to perform a rigorous comparison between the unfolded antineutrino spectrum and a theoretical model prediction that avoids the input model bias of the unfolding method.展开更多
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the financial assistance received from Science and Engineering Research Board(SERB PDF/2017/002594),New Delhi,India。
文摘Stainless steels have received wide attention as a substitute material for bipolar plates in high temperature proton exchange membrane fuel cell(HT-PEMFC).In the present work,the CrN,CrAlN and multilayer CrN/CrAlN coatings were deposited on 316 L SS to increase the corrosion resistance and decrease the interfacial contact resistance.The deposited coatings exhibited face centered cubic phase structure and it was verified from the X-ray diffraction pattern.X-ray photo electron spectroscopy results showed the formation of both CrN and CrAlN layers on 316 L SS.CrN/CrAlN coating is more helpful in water management due to low surface roughness and high contact angle in the HT-PEMFC environment.The corrosion resistance behavior of all the samples were studied in 85%H_(3)PO_(4)solution at 140℃purged with H_(2)(HT-PEMFC anode)and O_(2)(HT-PEMFC cathode)gases.The results showed that all the coatings considerably improved the performance of 316 L SS and superior corrosion resistance was observed for CrN/CrAlN multilayer coating,whose protective efficiency was 98.12%and 96.14%in the two simulated HT-PEMFC environments.The results of electrochemical impedance spectroscopic studies demonstrated higher impedance for CrN/CrAlN coating.Surface morphological studies performed after corrosion studies revealed that protection ability of CrN/CrAlN coating still remained acceptable.A very low interfacial contact resistance value of 6 mΩ cm^(2) at 140 N/cm;was observed for CrN/CrAlN coating.Moreover,after corrosion studies,the interfacial contact resistance value of CrN/CrAlN coated 316 L was much lower than that of CrN and CrAlN coatings due to the increased oxidation resistance.The maximum power density of about 0.93 W/cm^(2) at 2 A/cm^(2) and output voltage of 0.96 V was observed for CrN/CrAlN coating.
基金Daya Bay is supported in part by the Ministry of Science and Technology o f China, the U.S. Department o f Energy, the Chinese Academy of Sciences, the CASCenter for Excellence in Particle Physics, the National Natural Science Foundation of China, the Guangdong provincial government, the Shenzhen municipal government,the China General Nuclear Power Group, Key Laboratory of Particle and Radiation Imaging (Tsinghua University), the Ministry of Education, Key Laboratory ofParticle Physics and Particle Irradiation (Shandong University), the Ministry o f Education, Shanghai Laboratory for Particle Physics and Cosmology, the ResearchGrants Council o f the Hong Kong Special Administrative Region of China, the University Development Fund of the University of Hong Kong, the MOE program forResearch of Excellence at National Taiwan University, National Chiao-Tung University, NSC fund support from Taiwan, the U.S. National Science Foundation, the AlfredP. Sloan Foundation, the Ministry o f Education, Youth, and Sports of the Czech Republic, the Charles University GAUK (284317), the Joint Institute o f NuclearResearch in Dubna, Russia, the National Commission of Scientific and Technological Research of Chile, and the Tsinghua University Initiative Scientific Research Program.
文摘The establishment of a possible connection between neutrino emission and gravitational-wave(GW)bursts is important to our understanding of the physical processes that occur when black holes or neutron stars merge.In the Daya Bay experiment,using the data collected from December 2011 to August 2017,a search was per-formed for electron-antineutrino signals that coincided with detected GW events,including GW150914,GW151012,GW151226,GW170104,GW170608,GW 170814,and GW 170817.We used three time windows of±10,±500,and±1000 s relative to the occurrence of the GW events and a neutrino energy range of 1.8 to 100 MeV to search for correlated neutrino candidates.The detected electron-antineutrino candidates were consistent with the expected background rates for all the three time windows.Assuming monochromatic spectra,we found upper limits(90%confidence level)of the electron-antineutrino fluence of(1.13-2.44)×10^(11)cm^(-2)at 5 MeV to 8.0×10^(7)cm^(-2)at 100 MeV for the three time w indows.Under the assumption of a Fermi-Dirac spectrum,the upper limits were found to be(5.4-7.0)×10^(9)cm^(2)for the three time windows.
基金Supported in part by the Ministry of Science and Technology of Chinathe U.S.Department of Energy,the Chinese Academy of Sciences,the CAS Center for Excellence in Particle Physics,the National Natural Science Foundation of China+3 种基金the Guangdong provincial governmentthe Shenzhen municipal government,the China General Nuclear Power Group,the Research Grants Council of the Hong Kong Special Administrative Region of China,the Ministry of Education in TWthe U.S.National Science Foundation,the Ministry of Education,Youth,and Sports of the Czech Republic,the Charles University Research Centre UNCE,the Joint Institute of Nuclear Research in Dubna,Russiathe National Commission of Scientific and Technological Research of Chile。
文摘The prediction of reactor antineutrino spectra will play a crucial role as reactor experiments enter the precision era.The positron energy spectrum of 3.5 million antineutrino inverse beta decay reactions observed by the Daya Bay experiment,in combination with the fission rates of fissile isotopes in the reactor,is used to extract the positron energy spectra resulting from the fission of specific isotopes.This information can be used to produce a precise,data-based prediction of the antineutrino energy spectrum in other reactor antineutrino experiments with different fission fractions than Daya Bay.The positron energy spectra are unfolded to obtain the antineutrino energy spectra by removing the contribution from detector response with the Wiener-SVD unfolding method.Consistent results are obtained with other unfolding methods.A technique to construct a data-based prediction of the reactor antineutrino energy spectrum is proposed and investigated.Given the reactor fission fractions,the technique can predict the energy spectrum to a 2%precision.In addition,we illustrate how to perform a rigorous comparison between the unfolded antineutrino spectrum and a theoretical model prediction that avoids the input model bias of the unfolding method.