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2nd Sino-French Workshop on the Dark Universe

2nd Sino-French Workshop on the Dark Universe. Daya Bay Reactor Neutrino Experiment. Changgen Yang Institute of High Energy Physics, Beijing for the Daya Bay Collaboration. The 4th International Conference on Flavor Physics, Sept 24-28, 2007, Beijing. Outline. Physics Motivation

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2nd Sino-French Workshop on the Dark Universe

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  1. 2nd Sino-French Workshop on the Dark Universe Daya Bay Reactor Neutrino Experiment Changgen Yang Institute of High Energy Physics, Beijing for the Daya Bay Collaboration The 4th International Conference on Flavor Physics, Sept 24-28, 2007, Beijing

  2. Outline • Physics Motivation • Requirements • The Daya Bay Experiment • Layout • Detector (AD and Muon system) Design • Backgrounds • Systematic Errors and Sensitivity • Site Survey • Civil Construction • Summary

  3. ? ? reactor and accelerator atmospheric, K2K SNO, solar SK, KamLAND 0 13 = ? 23 = ~ 45° 12 ~ 32° 13The Last Unknown Neutrino Mixing Angle UMNSP Matrix • What isefraction of3? • Ue3 is a gateway to CP violationin neutrino sector: P(  e) - P(  e)  sin(212)sin(223)cos2(13)sin(213)sin

  4. Current Knowledge of 13 At m231 = 2.5  103 eV2, sin22 < 0.15 Global fit Direct search Sin2(213) < 0.09 Sin2213 < 0.18 allowed region Best fit value of m232 = 2.4103 eV2 Fogli etal., hep-ph/0506083

  5. sin2 2q13 = 0.01 • No good reason(symmetry) for sin22q13 =0 • Even if sin22q13 =0 at tree level, sin22q13 will not vanish at low energies with radiative corrections • Theoretical models predict sin22q13 ~ 0.001-0.1 Typical precision: 3-6% An experiment with a precision for sin22q13 better than 0.01 is desired An improvement of an order of magnitude over previous experiments

  6. Daya Bay: Goals And Approach • Utilize the Daya Bay nuclear power facilities to: • - determine sin2213 with a sensitivity of 1% • - measure m231 • Adopt horizontal-access-tunnel scheme: • - mature and relatively inexpensive technology • - flexible in choosing overburden and changing baseline • - relatively easy and cheap to add experimental halls • - easy access to underground experimental facilities • - easy to move detectors between different • locations with good environmental control. • Employ three-zone antineutrino detectors.

  7. How to reach 1% precision ? • Increase statistics: • Powerful nuclear reactors(1 GWth: 6 x 1020e/s) • Larger target mass • Reduce systematic uncertainties: • Reactor-related: • Optimize baseline for best sensitivity and smaller residual errors • Near and far detectors to minimize reactor-related errors • Detector-related: • Use “Identical” pairs of detectors to do relative measurement • Comprehensive program in calibration/monitoring of detectors • Interchange near and far detectors (optional) • Background-related • Go deep to reduce cosmic-induced backgrounds • Enough active and passive shielding

  8. 45 km 55 km The Daya Bay Nuclear Power Facilities Ling Ao II NPP: 2  2.9 GWth Ready by 2010-2011 Ling Ao NPP: 22.9 GWth 1 GWth generates 2 × 1020eper sec • 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 Daya Bay NPP: 22.9 GWth

  9. Where To Place The Detectors ? • Since reactor eare low-energy, it is a disappearance experiment: Small-amplitude oscillation due to 13integrated over E Large-amplitude oscillation due to 12 • 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 Sin22q13 = 0.1 Dm231 = 2.5 x 10-3 eV2 Sin22q12 = 0.825 Dm221 = 8.2 x 10-5 eV2 far detector near detector

  10. Far site 1615 m from Ling Ao 1985 m from Daya Overburden: 350 m Daya Bay Near site 363 m from Daya Bay Overburden: 98 m 4 x 20 tons target mass at far site Daya Bay Layout Ling Ao Near site ~500 m from Ling Ao Overburden: 112 m 900 m Ling Ao-ll NPP (under construction) 22.9 GW in 2010 465 m Water hall Construction tunnel 810 m Ling Ao NPP, 22.9 GW Filling hall entrance 295 m Daya Bay NPP, 22.9 GW Total length: ~3100 m

  11. Daya Bay Detector Veto muon system RPC Water Cerenkov Anti-neutrino Detector

  12. Anti-neutrino Detector modules • Three zones modular structure: I. target: Gd-loaded scintillator II. g-catcher: normal scintillator III. Buffer shielding: oil • Reflector at top and bottom • 192 8”PMT/module • Photocathode coverage: 5.6 %  12%(with reflector) 20 t Gd-LS LS oil sE/E = 12%/E sr = 13 cm Target: 20 t, 1.6m g-catcher: 20t, 45cm Buffer: 40t, 45cm

  13. Inverse-beta Signals Antineutrino Interaction Rate (events/day per 20 ton module) Daya Bay near site 960 Ling Ao near site 760 Far site 90 Ee+(“prompt”) [1,8] MeV En-cap (“delayed”)  [6,10] MeV tdelayed-tprompt [0.3,200] s Prompt Energy Signal Delayed Energy Signal 1 MeV 8 MeV 6 MeV 10 MeV Statistics comparable to a single module at far site in 3 years.

  14. Gd-loaded Liquid Scintillator • Baseline recipe: Linear Alkyl Benzene (LAB) doped with organic Gd complex (0.1% Gd mass concentration) • LAB (suggested by SNO+): high flashpoint, safer for environment and health, commercially produced for detergents. Stability of light attenuation two Gd-loaded LAB samples over 4 months

  15. Calibrating Energy Cuts • Automated deployed radioactive sources to calibrate the detector energy and position response within the entire range. • 68Ge (0 KE e+ = 20.511 MeV ’s) • 60Co (2.506 MeV ’s) • 238Pu-13C (6.13 MeV ’s, 8 MeV n-capture)

  16. Background reduction: redundant and efficient muon veto system • Multiple anti-neutrino detector modules for side-by-side cross check • Multiple muon tagging detectors: • Water pool as Cherenkov counter • Water modules along the walls and floor as muon tracker • RPC at the top as muon tracker • Combined efficiency > (99.5  0.25) %

  17. Backgrounds • Any set of events which mimics a delayed coincidence sequence is background • The primary backgrounds are: • The b-delayed neutron emitters: 9Li and 8He • Fast neutrons • Accidentals • All of the above can be measured Background to Signal Events Neutrino signal rate 930/day 760/day 90/day

  18. Systematic Uncertainty Budget Detector Related Uncertainties • Baseline is what we anticipate without further R&D • Goal is with R&D • We have made the modules portable so we can carry out swapping if necessary Reactor Related Uncertainties • By using near detectors, we can achieve the following relative systematic uncertainties: • With four cores operating 0.087 % • With six cores operating 0.126 %

  19. Summary of Systematic Uncertainties

  20. Far hall (80 t) Ling Ao near hall (40 t) Daya Bay near hall (40 t) Tunnel entrance Sensitivity of Daya Bay in sin2213 90% confidence level Super-K 90% CL Use rate and spectral shape

  21. Geotechnical Survey • No active or large fault • Earthquake is infrequent • Rock structure: massive and blocky granite • Rock mass: most is slightly weathered or fresh • Groundwater: low flow at the depth of the tunnel • Quality of rock mass: stable and hard Good geotechnical conditions for tunnel construction

  22. Tunnel and Experiment Hall Layout hall 3 hall 2 hall 4 hall 5 Main portal Seepage Water sump SAB & … hall 1

  23. Experiment Hall (#1) Auxiliary rooms Refuge Electricity

  24. Funding and supports • Funding Committed from China • Chinese Academy of Sciences, • Ministry of Science and Technology • Natural Science Foundation of China • China Guangdong Nuclear Power Group • Shenzhen municipal government • Guangdong provincial government • Total ~20 M$ • China will provide civil construction and ~half of the detector systems; • Support by funding agencies from other countries & regions IHEP & CGNPG • U.S. will provide ~half of the detector cost • Funding in the U.S. • R&D funding from DOE • CD2 review in Jan. 2008 • Funding from other organizations and regions is proceeding

  25. Daya Bay collaboration Europe (3) JINR, Dubna, Russia Kurchatov Institute, Russia Charles University, Czech Republic North America (14) BNL, Caltech, 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) IHEP, Beijing Normal Univ., Chengdu Univ. of Sci. and Tech., CGNPG, CIAE, Dongguan Polytech. Univ., Nanjing Univ.,Nankai Univ., Shenzhen Univ., Tsinghua Univ., USTC, Zhongshan Univ., Hong Kong Univ. Chinese Hong Kong Univ., Taiwan Univ., Chiao Tung Univ., National United Univ. ~ 190 collaborators

  26. Summary • Using the high-power Daya Bay Nuclear Power Plant and a large target mass of liquid scintillator, the Daya Bay Neutrino Experiment is poised to make the most sensitive measurement of sin2213. • Design of detectors is in progress and R&D is ongoing. • US CD2 Review scheduled on Jan. 2008. • Start civil construction in Oct. 2007, Daya Bay near detector operation in 2009, and full operation in 2010

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