大亚湾反应堆中微子实验 及其进展张家文中国科学院高能物理研究所报告内容 科学意义与目标 研究内容与方案 目前状况与预研进展 项目队伍、组织与管理 进度计划测量13的物理意义1）是自然界的基本参数 2）对理解轻子与夸克之间的关系，研究比目前 的粒子物理标准模型更基本的大统一理论具有 重要意义 3）对解释宇宙中物质-反物质不对称极为重要 如果sin22130.01，下一代长基线实验可以测定CP相 角。 如果sin221350% antracene) 长的衰减长度(10m) 长期稳定性(5year) 与有机玻璃不发生化学反应 过去的问题： 不稳定 Palo Verde : 55% antracene, 11m, 0.03%/day Chooz: 55% antracene, 10m, 0.4%/day 高能所目前已取得的成绩: 自制了测量液闪发光效率及衰减长度的设备 研究了清洁液闪的化学方法，特别是去除钍元素的办法 寻找与测试了国产原材料，均能满足要求 研制了多种满足前述要求的掺钆液闪液闪及其原料的测量结果SampleAtten. Len. (m)Light yield2: 8 mesitylene: dodecane(LS)15.0-LAB-PPO+ bis-MSB(Flour) in LS11.30.4590.2% Gd-EHA + Flour + LS8.30.528Flour + LAB23.70.5420.2%Gd-TMHA+Flour+LAB19.10.478Gd-loaded scintillator developed at IHEPHigh light yield, very transparent High flash point 147oC, environmentally friendly Low costLABStability of Gd-loaded scintillator developed at BNL研究单位： 高能所，BNL，JINR批量生产 液闪的配制 配方 混合程序 混合设备 原料 液闪的处理 放射性元素的去除 灰尘的去除 有害化学元素的去除 液闪的灌装 清洁度的保证 化学成分（一致性，杂质等） 的保证(H/C, Gd/H,) 体积与总重量的保证（ 5106 线性: 500 P.E. 噪声: 99.5% 效率误差 95% Muon 探测器, Eff. 90% RPC scintillator strips total ineff. = 10%*5% = 0.5% Neutron background vs water shielding thickness2m water水切伦科夫探测器 水池: 为国际上多个中微子实验采用 需 900 PMT 水箱: 为长基线中微子实验提出 已完成模型实验 需1248 PMT阻性板探测器(RPC) 在水箱上部精确标 记宇宙线事例 共三层, 2640 m2 读出道: 21200道 高能所在BESIII建 设中自行研制了具 有国际影 响的新 工艺光电倍增管读出电子学指标: 电荷动态范围: 0 500 p.e. 电荷分辨率: 10% 1 p.e. 噪声: 1KHz数字地形图：研究宇宙线本底及 实验大厅选址本底及其误差 非关联误差: U/Th/K/Rn/neutron 单gamma 记数率 0.9MeV 100 MWE + 2m waterY.F. Wang et al., PRD64(2001)00130128He/9Li: 250 MWE(near)，1000 MWE(far)T. Hagner et al., Astroparticle. Phys. 14(2000) 33 Near far Neutrino signal rate(1/day)56080 Natural backgrounds(Hz)45.345.3 Single neutron(1/day)242 Accidental BK/signal0.04%0.02% Correlated fast neutron Bk/signal 0.14%0.08% 8He+9Li BK/signal0.5%0.2%系统误差 Chooz Palo VerdeKamLAND Daya BayReactor power0.70.72.05 1MeV)502.72.01.40.8232Th(1MeV )501.20.90.70.440K(1MeV)101.8 1.30.90.5Total5.74.23.01.7Oil buffer thicknessWhy three zones ? Three zones: Complicated acrylic tank construction g backgrounds on walls Less fiducial volume Two zones: Neutrino energy spectrum distorted Neutron efficiency error due to energy scale and resolution:two zones: 0.4%, three zones 0.2% Using 4 MeV cut can reduce the error by a factor of two, but backgrounds from b+g do not allow us to do so2 zone3 zonecutcutCapture on GdCapture on HVessel boundary Reactor-related Uncertainties of Daya Bay# Reactor CoresSyst. error due to Power FluctuationsSyst. error due to Core PositionsTotalsyst. error40.035%0.08%0.087%60.097%0.08%0.126%Based on experience of past experiments, due to uncertainty inmeasuring the amount of thermal power produced, the uncorrelatederror per reactor core p 2%.frF and frN are fractions of the events at the far and near site from reactor r respectively. The error due to power fluctuations of the reactors is given by: Energy Cuts3 zoneCut, error 0.2%Cut, error0.05%Dominated by energy scale KamLAND 1%Time CutsNeutron time window uncertainty: t = 10 ns 0.03% uncertainty Use common clockg Baseline = 0.1% g Goal = 0.03%1.5% Loss0.15% LossLivetime Measure relative livetimes using accurate common clock Use LED to simulate neutrino events Should be negligible errorTarget Volume Can be cancelled by swapping KamLAND: 1% CHOOZ: 0.02%? Flowmeters 0.02% repeatabilityg Baseline = 0.2% g Goal = 0.02%H/C and H/Gd ratio Can be cancelled by swapping H/C ratio CHOOZ claims 0.8% absolute based on multiple lab analyses (combustion) Use well defined liquid such as LAB and dodecane R&D: measure via NMR or neutron capture Expected error: 0.1%-0.2% H/Gd ratio Can be measured by neutron activated x-rays and neutron capture time For t = 0.5 ms, error 0.02%Cosmic-muons at the laboratory350 m97 m98 m210 mDYBLAMidFar Elevation (m)9798208347Flux (Hz/m2)1.20.730.170.045Energy (GeV)556097136Apply modified Gaisser parametrization for cosmic-ray flux at surfaceUse MUSIC and mountain profile to estimate muon flux & energyFast neutron spectrum from MCPrecision to determine the 9Li background in situSpectrum of accidental background