Daya Bay Neutrino Experiment Huang Xingtao Shandong University, Jinan, China On Behalf of the Daya Bay Collaboration

2 Neutrino Oscillation Parameterize the PMNS matrix as: Solar, reactorreactor and accelerator 0  Atmospheric, accelerator  23 ~ 45°  12 ~ 32°  13 = ?  13 is the gateway of CP violation in lepton sector! Weak eigenstate( )  mass eigenstate ( )  Pontecorvo-Maki-Nakagawa-Sakata (PMNS) Matrix

3 experimental knowledge on  13 Direct search (PRD 62, ) Global fit (arXiv: v2)

4 Big competition Angra, Brazil R&D phase Diablo Canyon, USA Braidwood, USA Double Chooz, France sin 2 2  13 ~0.03 Krasnoyarsk, Russia KASKA, Japan Daya Bay, China sin 2 2  13 ~0.01 RENO, Korea sin 2 2  13 ~ proposals 4 cancelled 4 in progress Advantages of Daya Bay: 1)very high antineutrino flux; 2) mountains to suppress cosmic-ray-induced backgrounds

5 Ling Ao II NPP: 2  2.9 GWth Ready by Ling Ao NPP: 2  2.9 GW th Daya Bay NPP: 2  2.9 GW th 1 GW th generates 2 ×  e per sec 55 km 45 km Daya Bay nuclear power plant 12th most powerful in the world (11.6 GW) Top five most powerful by 2011 (17.4 GW) Adjacent to mountain, easy to construct tunnels to reach underground labs with sufficient overburden to suppress cosmic rays

6 Detection of  e Coincidence of prompt positron and delayed neutron signals helps suppress background events Inverse  -decay in Gd-doped liquid scintillator: Delayed Energy Signal Prompt Energy Signal. 1 MeV8 MeV 6 MeV10 MeV E e+ (“prompt”)  [1,8] MeV E n-cap (“delayed”)  [6,10] MeV t delayed -t prompt  [0.3,200]  s n-p n-Gd

7 Place near detector(s) close to reactor(s) to measure raw flux and spectrum of  e, reducing reactor-related systematic Position a far detector near the first oscillation maximum to get the highest sensitivity, and also be less affected by  12 How to measure  13 ? The Survival Probability is described by:

8 How to measure  13 ? Measured ratio of Rates Proton Number Ratio Detector Efficiency Ratio sin 2 2  13 Filling Gd-LS and Mass measurement Calibration Systems

9 Total length: ~3100 m Daya Bay NPP, 2  2.9 GW Ling Ao NPP, 2  2.9 GW Ling Ao-ll NPP (under construction) 2  2.9 GW in m Daya Bay Near site 363 m from Daya Bay Overburden: 98 m Far site 1615 m from Ling Ao 1985 m from Daya Overburden: 350 m 4 x 20 tons target mass at far site Ling Ao Near site ~500 m from Ling Ao Overburden: 112 m 810 m 465 m 900 m entrance Filling hall Construction tunnel Water hall Daya Bay Layout Horizontal Tunnel Total length 3200 m

10 How to measure sin 2 2  13 to 0.01 So Far, CHOOZ: R=1.01  2.8%(stat)  2.7%(syst), sin 2 2  13 <0.17 Goal: sin 2 2  13 < 90% CL in 3 years.  Increase statistics Need intensive antineutrino flux from powerful nuclear reactors Antineutrino source ( Powerful Power Plant) Currently 4 cores 11.6 GW and will be 6 cores 17.4 GW from 2011 Utilize larger target mass, hence larger detectors Multiple detectors (totally 160 ton Gd-LS as targets)

11  Reduce systematic uncertainties: Reactor-related: Optimize baseline for best sensitivity and smaller residual errors Horizontal tunnel to make detectors removable Near and far detectors to minimize reactor-related errors Detector-related: Use “Identical” pairs of detectors to do relative measurement All detectors are filled at the filling hall and use the same batch of Gd-LS. Comprehensive program in calibration/monitoring of detectors Side-by-side calibration Interchange near and far detectors (optional) Background-related Go deeper to reduce cosmic-induced backgrounds Enough active and passive shielding B/S ~0.4% Near B/S ~0.2% Far How to measure sin 2 2  13 to 0.01

12 How to measure sin 2 2  13 to 0.01 The sensitivity of ≤ 0.01 for sin 2 2  13 will be reached after 3 years data taking Number of years of data taking Sensitivity in sin 2 2  13 (90%CL) 0.38% relative detector syst. uncertainty  m 2 31 = 2.5  10  3 eV 2

13 Daya Bay Detectors

14 Gd-Loaded LS LS Mineral Oil 5 m 1.55 m 1.99 m 2.49 m Calibration System PMT 5 m Anti-neutrino Detector( AD) Design  Three zones modular structure: I.Target: 20t, Gd-loaded scintillator II.  -catcher: 20t, normal scintillator III.Buffer shielding: 40t, oil  Reflector at top and bottom  192 8”PMT/module  E /E = 12%/  E  12% / E 1/2 Acrylic Vessels

15 Muon Veto System Multiple muon tagging detectors: –Water pool as Cherenkov counter has inner/outer regions –RPC at the top as muon tracker –Combined efficiency – > (99.5  0.25) %

16 Calibration System The 3 automated systems per detector perform weekly or monthly routine monitoring of detector. – γ(LED) source : Monitoring system for optical properties –Radioactive sources for energy calibration 68 Ge: positron source 252 Cf : neutron source

17 Gd-Liquid Scintillator Daya Bay experiment will use 200 ton normal liquid scintillator and 200 ton 0.1% gadolinium-loaded liquid scintillator (Gd-LS). Gd-TMHA + LAB + 3g/L PPO + 15mg/L bis-MSB The stability of the Gd-LS has been tested for two years with IHEP prototype detector (half ton Gd-LS) and high temperature aging tests in lab. All Gd-LS will be produced as one batch on-site, to ensure IDENTICAL detectors. The mixing equipment has been tested at IHEP and will be re- assembled on-site. 4-ton test batch production in April Excellent long-term LS stability in prototype

18 Offline Software Progress “NuWa( 女娲 )”: Day Bay Offline Software System –Designed with “Object-Oriented” Tech. and implemented with C++ Language. –Platforms to run: SLC, Mac, Fedora and so on. –Based on the Gaudi Framework developed by LHCb and extensively used by ATLAS, GLAST and BESIII. –Physics and detector simulation via Geant4 –Deploy ROOT Storage Technology. –From generation to simple physics analysis Chain has been build. Online and offline software are being integrated together. –Regular releases ( NuWa will be released soon) NuWa Statue

19 Civil Construction Control Room Surface Assembly Building Entrance Inside tunnel

20 Getting To Build The Detectors 4-m vessel in the U.S. Stainless steel tank in China 3-m acrylic vessel in Taiwan SS Tank delivery Delivery of 4m AVStainless steel tank in SAB

21 More on Detector Preparation Stick the ESR® high reflec. film on to the acrylic panel Practice installing bottom reflector Rehearsing installation of AD PMT assembly Checking out liquid- scintillator production plant Production of RPCs 0.1% Gd-LS in 5000-L tank

22 Tentative Schedule  : Proposal, R&D, engin. design etc.  October 2007: Ground Breaking  Spring 2008: CD3 review completed  March 2009: Surface Assembly Building occupancy  Summer 2010: Daya Bay Near Hall ready for data taking  Summer 2011: All near and far halls ready for data taking Three years’ data taking will reach full sensitivity.

23 The Daya Bay Collaboration Europe (3) (9) JINR, Dubna, Russia Kurchatov Institute, Russia Charles University, Czech Republic North America (15)(~83) BNL, Caltech, Cincinnati, George Mason Univ., LBNL, Iowa State Univ., Illinois Inst. Tech., Princeton, RPI, UC-Berkeley, UCLA, Univ. of Houston, Univ. of Wisconsin, Virginia Tech., Univ. of Illinois-Urbana-Champaign Asia (18) (~126) IHEP, Beijing Normal Univ., Chengdu Univ. of Sci. and Tech., CGNPG, CIAE, Dongguan Polytech. Univ., Nanjing Univ., Nankai Univ., Shandong Univ., Shenzhen Univ., Tsinghua Univ., USTC, Zhongshan Univ., Univ. of Hong Kong, Chinese Univ. of Hong Kong, National Taiwan Univ., National Chiao Tung Univ., National United Univ. ~ 218 collaborators Thanks for your attention!