1. S. Kettell WIN09 9/13/09 Daya Bay Experiment Steve Kettell BNL On Behalf of the Daya Bay Collaboration

2. S. Kettell WIN09 9/13/09 2 The Last Mixing Angle:  13 U MNSP Matrix Maki, Nakagawa, Sakata, Pontecorvo What is  e fraction of 3 ? Is there  symmetry in neutrino mixing? Will we be able to observe CP violation? U e3 is the gateway to leptonic CP violation. ? ? atmospheric, K2K reactor and accelerator 0  SNO, solar SK, KamLAND  12 ~ 32°  23 = ~ 45°  13 = ?

3. S. Kettell WIN09 9/13/09 3 Detection of  e Calibrate with 68 Ge, neutron, and 60 Co additional calibration with LED and spallation neutrons Inverse  -decay in Gd-doped liquid scintillator: Prompt Energy Signal. 1 MeV 6 MeV 10 MeV E e+ = [1,8] MeV E n (delayed) = [6,10] MeV t delayed -t prompt = [0.3,200]  s n-p n-Gd  e  p  e + + n (prompt)  + p  D +  (2.2 MeV) (delayed)  + Gd  Gd*  Gd +  ’s (8 MeV) (delayed) 0.3b 50kb Delayed Energy Signal

4. S. Kettell WIN09 9/13/09 4 Measuring  13 at a Reactor ~1.8 km ~ 0.3-0.5 km Distance (km) PeePee nuclear reactor detector 1 detector 2  13 Precise measurement No dependence on  CP or matter effects Gd-LS LS MO near detectors measure e flux and spectrum to reduce reactor- related systematic uncertainties far detector at the oscillation max provides the highest sensitivity Disappearance Probability

5. S. Kettell WIN09 9/13/09 5 Measured Ratio of Rates Detector Efficiency Ratio Detector Mass Ratio, H/C Measure ratio of interaction rates in multiple detectors nearfar νeνe distance L ~ 1.5 km Measurement Concept mass measurement calibration sin 2 2  13 ± 0.3%± 0.2% Gd-LS Storage Tank Far Near

6. S. Kettell WIN09 9/13/09 6 Daya Bay NPP: 2  2.9 GW th Ling Ao II: 2  2.9 GW th 2010-11 Ling Ao: 2  2.9 GW th 1 GW th generates 2 × 10 20  e /s Total tunnel length: ~2700 m 730 m 570 m 910 m Daya Bay Near 360 m from Daya Bay Overburden: 97 m Ling Ao Near 500 m from Ling Ao Overburden: 98 m Far site 1600 m from Ling Ao 2000 m from Daya Overburden: 350 m Water hall Filling hall Total Power Now: 11.6 GW th 2011: 17.4 GW th

7. S. Kettell WIN09 9/13/09 7 Daya Bay Detectors Ancillary Rooms - Gas - DAQ - Water 8 Antineutrino detectors 4 in far hall, 2 in each near hall 20t target mass per AD Muon Veto system

8. S. Kettell WIN09 9/13/09 8 Muon Veto System Multiple muon detectors:  Water pool Cherenkov counter: inner/outer regions, 2.5m shield  RPC muon tracker  Combined efficiency (99.5  0.25)% 1m outer water veto 1.5m inner water veto Water Cerenkov (2 layers) RPC 960 8” PMTs (3 pools) AD

9. S. Kettell WIN09 9/13/09 9 Gd-LS LS MO 5 m 1.55 m 1.99 m 2.49 m Calibration System Reflectors Anti-neutrino Detector (AD) Design  E /E = 12%/  E  12% / E 1/2 Acrylic Vessels PMT Total Weight = 110t  Eight identical 3-zone detectors: I.Target: 20t Gd-LS II.  -catcher: 20t LS III.Buffer shielding: 40t mineral oil  Top/bottom reflectors  192 8”PMT/module

10. S. Kettell WIN09 9/13/09 10 (Gd) Liquid Scintillator 500L fluor-LAB Two 1000L 0.5% Gd- LAB 5000L 0.1% Gd- LS 0.1% Gd-LS in 5000L tank Daya Bay experiment uses 185 ton 0.1% gadolinium-loaded liquid scintillator (Gd- LS). Gd-TMHA + LAB + 3g/L PPO + 15mg/L bis-MSB 4-ton test batch production in March 2009. Gd-LS will be produced in multiple batches but mixed in reservoir on-site to ensure identical detectors. Gd-LS stability in 4T test

11. S. Kettell WIN09 9/13/09 11 Daya Bay Background 9 Li  signal backgrounds from beta-delayed neutron emission isotopes 8 He and 9 Li will have to be measured and subtracted 840 4 near detectors

12. S. Kettell WIN09 9/13/09 12 Systematic Uncertainties Absolute measurement Relative measurement O(0.2-0.3%) precision for relative measurement between detectors at near and far sites Detector-Related Uncertainties Ref: Daya Bay TDR CHOOZ: R=1.01  2.8%(stat)  2.7%(syst), sin 2 2  13 <0.17

13. S. Kettell WIN09 9/13/09 13 Daya Bay Sensitivity Sensitivity : sin 2 2 θ 13 < 0.01 @ 90% CL after 3 years of data taking Steps to Physics: Dry-Run near site operations Full operations 0 1 2 3 4 5 0.05 0.04 0.03 0.02 0.01 0. 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 SourceUncertainty Reactor power0.13% Detector (per module)0.38% (baseline) Signal statistics0.2%

14. S. Kettell WIN09 9/13/09 14 August 2009 Daya Bay Project Status CD-0 (DOE Mission Need): 11/2005 Daya Bay proposed at OHEP Briefing 4/2006 Successful Physics Review 10/16/06 CD-1 site selection approved 9/2007 Groundbreaking for civil construction 10/2007 CD-2 Baseline approved 3/2008 CD-3b Construction start 8/2008 Occupancy of SAB 3/2009 Occupancy of first underground halls, fall 2009 Expected start of first operations, summer 2010 Full operations start, summer 2011 Far hall Daya Bay hall Ling Ao hall LS hall

15. S. Kettell WIN09 9/13/09 15 Civil Construction Control Room Surface Assembly Building Entrance Daya Bay Near Hall - July 09

16. S. Kettell WIN09 9/13/09 16 Detector Assembly 4-m vessel in the U.S. 3-m acrylic vessel in Taiwan SS Vessel delivery to SAB ReflectorPrototype assembly in SAB 0.1% Gd-LS in 5000-L tank

17. S. Kettell WIN09 9/13/09 17 Summary and Conclusions The Daya Bay experiment is the most sensitive reactor θ 13 experiment under construction and is designed to measure sin 2 2θ 13 < 0.01 at 90% CL with 3 years of data taking. Daya Bay will use eight “identical” antineutrino detectors to achieve a relative detector systematic error < 0.38%. The 3-zone detector design allows the observation of the antineutrino signal without fiducial cuts. Civil and detector construction are progressing well. Data taking at the near site is scheduled to begin in summer 2010 with 2 detectors, which will allow extensive studies of systematics. The full experiment will begin in summer 2011. Detectors are movable. Swapping can be considered after some running to further reduce systematic uncertainties but is not required to reach the baseline sensitivity.

18. S. Kettell WIN09 9/13/09 18 Daya Bay Collaboration Europe (3) (9) JINR, Dubna, Russia Kurchatov Institute, Russia Charles University, Czech Republic Asia (19) (~135) IHEP, Beijing Normal U., Chengdu U. of Sci. and Tech., CGNPG, CIAE, Dongguan Polytech. U., Nanjing U., Nankai U., Shandong U., Shanghai Jiaotong U., Shenzhen U., Tsinghua U., USTC, Zhongshan U., U. of Hong Kong, Chinese U. of Hong Kong, National Taiwan U., National Chiao Tung U., National United U. United States (15)(~89) BNL, Caltech, U. Cincinnati, George Mason U, LBNL, Iowa State U, Illinois Inst. Tech., Princeton, RPI, UC-Berkeley, UCLA, U. of Houston, U. of Wisconsin, Virginia Tech., U. of Illinois-Urbana-Champaign ~ 230 collaborators

19. S. Kettell WIN09 9/13/09 19 Backup

20. S. Kettell WIN09 9/13/09 20 Phase-I, started in 2006, ended in Jan. 2007

21. S. Kettell WIN09 9/13/09 21 IHEP Prototype (0.1% Gd-LS) Gd-TMHA complex synthesis Phase-II, filled with half-ton 0.1% Gd-LS, started in Jan. 2007 and keep running until now. The prototype is also used for the FEE and Trigger boards testing. Gd-TMHA complex synthesis

22. S. Kettell WIN09 9/13/09 22 Calibration system automated calibration system Automated calibration system → routine weekly deployment of sources LED light sources → monitoring optical properties e + and n radioactive sources (=fixed energy) → energy calibration 68 Ge source Am- 13 C + 60 Co source LED diffuser ball

23. S. Kettell WIN09 9/13/09 23 Daya Bay Antineutrino Detectors 3-Zone Design no position reconstruction, no fiducial cut for event identification Gd-LS (20 tons) = 5m (tunnel limitations) oil buffer (MO) thickness > 15cm buffer between PMT and OAV gamma catcher (LS) thickness thickness = 42.3 cm det. efficiency > 91.5% LS MO Efficiency (%)

24. S. Kettell WIN09 9/13/09 24 Detector Top/Bottom Reflectors z (cm) reflector flattens detector response specular reflectors consist of ESR® high reflectivity film on acrylic panels total p.e without reflector with reflector

25. S. Kettell WIN09 9/13/09 25 Antineutrino Detector Response Detector Uniformity along radial R directionalong vertical symmetry axis (z-direction) Gd-LS boundary - GEANT4-based simulations - idealized 3-zone detector plus reflectors - developing realistic geometry in simulations

26. S. Kettell WIN09 9/13/09 26 Detector Calibration z(cm) automated calibration system → routine weekly deployment of sources LED light sources → monitoring optical properties e + and n radioactive sources (=fixed energy) → energy calibration R(cm)  /E = 0.5% per pixel requires: 1 day (near), 10 days (far) tagged cosmogenic background (free) → fixed energy and time 68 Ge source Am-C + 60 Co source LED diffuser ball

27. S. Kettell WIN09 9/13/09 27 Energy calibration Prompt Energy Signal 1 MeV8 MeV 6 MeV10 MeV Delayed Energy Signal e + threshold: stopped positron signal using 68 Ge source (2x0.511 MeV) e + energy scale: 2.2 MeV neutron capture signal (n source, spallation) 1 MeV cut for prompt positrons: >99%, uncertainty negligible 6 MeV cut for delayed neutrons: 91.5%, uncertainty 0.22% assuming 1% energy uncertainty 6 MeV threshold: n capture signals at 8 and 2.2 MeV (n source, spallation) efficiency 78% efficiency 98%  e + p → e + + n

28. S. Kettell WIN09 9/13/09 28 Target mass measurement filling platform with clean room ISO Gd-LS weighing tank pump stations detector load cell accuracy < 0.02% Coriolis mass flowmeters < 0.1% 200-ton Gd-LS reservoir 20-ton ISO tank filling “pairs” of detectors Gd-LS MO LS

29. S. Kettell WIN09 9/13/09 29 Fission process in nuclear reactor produces huge number of low-energy antineutrino A typical commercial reactor, with 3 GW thermal power, produces 6×10 20 ν e /s A typical commercial reactor, with 3 GW thermal power, produces 6×10 20 ν e /s Daya Bay reactors produce 11.6 GW th now, 17.4 GW th in 2011 Daya Bay reactors produce 11.6 GW th now, 17.4 GW th in 2011 Nuclear reactors as antineutrino source Arbitrary Flux Cross Section From Bemporad, Gratta and Vogel The observable antineutrino spectrum is the product of the flux and the cross section The observable antineutrino spectrum is the product of the flux and the cross section Antineutrino spectrum

30. S. Kettell WIN09 9/13/09 30 Proposed Reactor Experiments 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 ~0.03 8 proposals 4 cancelled 4 in progress Advantages of Daya Bay: 1)very high antineutrino flux; 2) mountains to suppress cosmic-ray-induced backgrounds