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The Daya Bay Experiment

The Daya Bay Experiment. Kam-Biu Luk (UC Berkeley & LBNL) for The Daya Bay Collaboration P5 Review, Fermilab, April 18, 2006.  13  The Last Unknown Neutrino Mixing Angle. ?. Reactor, accelerator. atmospheric, Accelerator. SNO, solar SK, KamLAND. 0 .  23 = ~ 45°.  13 = ?.

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The Daya Bay Experiment

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  1. The Daya Bay Experiment Kam-Biu Luk (UC Berkeley & LBNL) for The Daya Bay Collaboration P5 Review, Fermilab, April 18, 2006

  2. 13The Last Unknown Neutrino Mixing Angle ? Reactor, accelerator atmospheric, Accelerator SNO, solar SK, KamLAND 0 23 = ~ 45° 13 = ? 12 ~ 32° ? UMNSP Matrix Maki, Nakagawa, Sakata, Pontecorvo • What isefraction of3? • Ue3 is a gateway to CP violationin neutrinos: 2345 P(  e) - P(  e)  sin(212)sin(223)cos2(13)sin(213)sin P5 Review (Kam-Biu Luk)

  3. Current Knowledge of 13 At m231 = 2.5  103 eV2, sin22 < 0.15 Experimental allowed at 3 Number of predictions Direct search Theoretical predications allowed region P5 Review (Kam-Biu Luk)

  4. Recommendations • APS Neutrino Study Group: • Neutrino Scientific Assessment Group: P5 Review (Kam-Biu Luk)

  5. Limitations of Past and CurrentReactor Neutrino Experiments Palo Verde, CHOOZ • Typical precision is 3-6% • due to • limited statistics • reactor-related systematic • errors: • - energy spectrum of e • (~2%) • - time variation of fuel • composition (~1%) • detector-related systematic • error (1-2%) • background-related error • (1-2%) P5 Review (Kam-Biu Luk)

  6. How To Reach A Precision of 0.01 ? • Utilize a powerful nuclear power plant • Use large detectors to reduce statistical error • Use near and far detectors to minimize reactor-related errors • Optimize baseline to have best sensitivity and further reduce any residual reactor-related errors • Interchange near and far detectors to cancel some of the detector systematic uncertainty • Use sufficient shielding to reduce background • Carry out comprehensive calibration to reduce detector systematic error • Build almost identical detectors to reduce detector-related systematic error P5 Review (Kam-Biu Luk)

  7. 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 • - 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. P5 Review (Kam-Biu Luk)

  8. Where To Place The Detectors ? • Since reactor eare low-energy, it is a disappearance experiment: Small-amplitude oscillation due to 13 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 Sin2(2q13) = 0.1 Dm231 = 2.5 x 10-3 eV2 Sin2(2q12) = 0.825 Dm221 = 8.2 x 10-5 eV2 P5 Review (Kam-Biu Luk)

  9. Detecting Low-energy e e  p  e+ + n(prompt)  + p  D + (2.2 MeV) (delayed) • + Gd  Gd*  Gd + ’s(8 MeV) (delayed) From Bemporad, Gratta and Vogel Arbitrary Observable n Spectrum Cross Section Flux • The reaction is the inverse -decay in Gd-doped liquid scintillator: 0.3b 50,000b • Time- and energy-tagged signal is a good • tool to suppress background events. • Energy of eis given by: E Te+ + Tn + (mn - mp) + m e+  Te+ + 1.8 MeV 10-40 keV P5 Review (Kam-Biu Luk)

  10. The Daya Bay Collaboration: China-Russia-U.S. X. Guo, N. Wang, R. Wang Beijing Normal University, Beijing L. Hou, B. Xing, Z. Zhou China Institute of Atomic Energy, Beijing M.C. Chu, W.K. Ngai Chinese University of Hong Kong, Hong Kong J. Cao, H. Chen, J. Fu, J. Li, X. Li, Y. Lu, Y. Ma, X. Meng, R. Wang, Y. Wang, Z. Wang, Z. Xing, C. Yang, Z. Yao, J. Zhang, Z. Zhang, H. Zhuang, M. Guan, J. Liu, H. Lu, Y. Sun, Z. Wang, L. Wen, L. Zhan, W. Zhong Institute of High Energy Physics, Beijing X. Li, Y. Xu, S. Jiang Nankai University, Tianjin Y. Chen, H. Niu, L. Niu Shenzhen University, Shenzhen S. Chen, G. Gong, B. Shao, M. Zhong, H. Gong, L. Liang, T. Xue Tsinghua University, Beijing K.S. Cheng, J.K.C. Leung, C.S.J. Pun, T. Kwok, R.H.M. Tsang, H.H.C. Wong University of Hong Kong, Hong Kong Z. Li, C. Zhou Zhongshan University, Guangzhou Yu. Gornushkin, R. Leitner, I. Nemchenok, A. Olchevski Joint Institute of Nuclear Research, Dubna, Russia V.N. Vyrodov Kurchatov Institute, Moscow, Russia B.Y. Hsiung National Taiwan University, Taipei M. Bishai, M. Diwan, D. Jaffe, J. Frank, R.L. Hahn, S. Kettell, L. Littenberg, K. Li, B. Viren, M. Yeh Brookhaven National Laboratory, Upton, New York, U.S. R.D. McKeown, C. Mauger, C. Jillings California Institute of Technology, Pasadena, California, U.S. K. Whisnant, B.L. Young Iowa State University, Ames, Iowa, U.S. W.R. Edwards, K. Heeger, K.B. Luk University of California and Lawrence Berkeley National Laboratory, Berkeley, California, U.S. V. Ghazikhanian, H.Z. Huang, S. Trentalange, C. Whitten Jr. University of California, Los Angeles, California, U.S. M. Ispiryan, K. Lau, B.W. Mayes, L. Pinsky, G. Xu, L. Lebanowski University of HoU.S.ton, HoU.S.ton, Texas, U.S. J.C. Peng University of Illinois, Urbana-Champaign, Illinois, U.S. 20 institutions, 89 collaborators P5 Review (Kam-Biu Luk)

  11. P5 Review (Kam-Biu Luk)

  12. The Daya Bay Nuclear Power Facilities 45 km Ling Ao II NPP: 2  2.9 GWth Ready by 2010-2011 Ling Ao NPP: 2  2.9 GWth 55 km 1 GWth generates 2 × 1020 e per sec • 12th most powerful in the world • Top five most powerful by 2011 • 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 P5 Review (Kam-Biu Luk)

  13. Far site 1600 m from Ling Ao 2000 m from Daya Overburden: 350 m 910 m Mid site ~1000 m from Daya Overburden: 208 m 570 m 230 m (15% slope) 730 m 290 m (8% slope) Daya Bay Near 360 m from Daya Bay Overburden: 97 m Empty detectors: moved to underground halls through access tunnel. Filled detectors: swapped between underground halls via horizontal tunnels. Ling Ao Near 500 m from Ling Ao Overburden: 98 m Ling Ao-ll NPP (under const.) Ling Ao NPP Entrance portal Daya Bay NPP Total length: ~2700 m P5 Review (Kam-Biu Luk)

  14. A Versatile Site • Full operation: • (1) Two near sites + Far site • (2) Mid site + Far site • (3) Two near sites + Mid site + Far site • Internal checks, each with different • systematic • Rapid deployment: • - Daya near site + mid site • - 0.7% reactor systematic • error P5 Review (Kam-Biu Luk)

  15. Geotechnical Survey • Topological survey - complete • Geophysical survey - complete • Bore drilling - complete far Lingao near Topological survey: Length: 2.5 km (S-N) Width: 450 m ~ 1.3 km (E-W) Area: 1.839 km2 Scale: Along tunnel 1:2000 Portal area 1:500 mid Daya near P5 Review (Kam-Biu Luk)

  16. Geophysical Survey fault Electrical Resistivity method Lingao near mid mid Lingao near Planned tunnel Weathering bursa Daya near mid far P5 Review (Kam-Biu Luk)

  17. Bore Drilling bursa P5 Review (Kam-Biu Luk)

  18. P5 Review (Kam-Biu Luk)

  19. (in the weathering bursa) P5 Review (Kam-Biu Luk)

  20. Findings of Geotechnical Survey Chris Laughton (FNAL) Pat Dobson (LBL) Joe Wang (LBL) Yanjun Sheng (IGG) • 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 U.S. experts in geology and tunnel construction assist geotechnical survey: Good geotechnical conditions for tunnel construction P5 Review (Kam-Biu Luk)

  21. Tunnel construction • The total tunnel length is ~3 km • Preliminary cost estimate by professionals: ~$3K/m • Construction time is ~24 months • A similar tunnel exists on site as a reference 7.2 m 7.2 m P5 Review (Kam-Biu Luk)

  22. Cosmic-ray Muon ~350 m ~98 m ~210 m ~97 m • Apply modified Geiser parametrization for cosmic-ray flux at surface • Use MUSIC and mountain profile to estimate muon flux & energy P5 Review (Kam-Biu Luk)

  23. What Target Mass Should Be? m231 = 2  10-3 eV2 DYB: B/S = 0.5% LA: B/S = 0.4% Mid: B/S = 0.1% Far: B/S = 0.1% Solid lines : near+far Dashed lines : mid+far tonnes Systematic error (per site): Black : 0.6% Red : 0.25% Blue : 0.12% P5 Review (Kam-Biu Luk)

  24. Design of Antineutrino Detectors 20t Gd-doped LS buffer gamma catcher • Three-layerstructure: I. Target: Gd-loaded liquid scintillator II. Gamma catcher: liquid scintillator, 45cm III. Buffer shielding: mineral oil, ~45cm • Possibly with diffuse reflection at ends. For ~200 PMT’s around the barrel: Oil buffer thickness P5 Review (Kam-Biu Luk)

  25. Why three zones ? 3 zone 2 zone cut cut • Three zones: - Construction of acrylic vessels is more involved - More g background coming from the walls - Less fiducial mass • Two zones: • Neutrino energy spectrum is distorted • Error of neutron efficiency due to energy scale and resolution: two zones: 0.4%, three zones 0.2% CHOOZ • Using 4 MeV cut can reduce the error by a factor of two, • but backgrounds from b+g do not allow us to do so P5 Review (Kam-Biu Luk)

  26. Design of Shield-Muon Veto 2m of water ~0.05 Neutron background vs thickness of water • Detector modules enclosed by 2m of water to shield neutrons and gamma-rays from surrounding rock • Water shield also serves as a Cherenkov veto • Augmented with a muon tracker: scintillator or RPCs • Combined efficiency of Cherenkov and tracker > 99.5% P5 Review (Kam-Biu Luk)

  27. P5 Review (Kam-Biu Luk)

  28. Background • Natural Radioactivity: PMT glass, Rock, Radon in the air, etc • Slow neutron, and fast neutron • - Neutrons produced in rock and water shield (99.5% veto efficiency) • Cosmogenic isotopes: 8He/9Li which can -n decay - Cross section measured at CERN (Hagner et. al.) - Can be measured in-situ, even for near detector with muon rate ~ 10 Hz. • Use a modified Palo-Verde-Geant3-based MC to model response of detector: 20t module The above number is before shower-muon cut. P5 Review (Kam-Biu Luk)

  29. Systematic Uncertainty • * • No Vertex cut. • Residual detection error is dominated by the neutron energy cut at 6 MeV • arises mainly from the energy-scale uncertainties. (It is ~0.2% for a 1% • energy-scale error at 6 MeV. • Positron energy cut is negligible. Statistical Error (3 years): 0.2% Residual systematic error: ~ 0.2% P5 Review (Kam-Biu Luk)

  30. Sensitivity of sin2213 • Daya Bay site - baseline = 360 m - target mass = 40 tonne - B/S = ~0.5% • LingAo site - baseline = 500 m - target mass = 40 tonne - B/S = ~0.5% • Far site - baseline = 1900 m to DYB cores 1600 m to LA cores - target mass = 80 tonne - B/S = ~0.2% • Three-year run (0.2% statistical error) • Detector residual error = 0.2% • Use rate and spectral shape 90% confidence level Near-mid 2 near + far near (40t) + mid (40 t) 1 year P5 Review (Kam-Biu Luk)

  31. sin2213 = 0.02 sin2213 = 0.1 Precision of m231 P5 Review (Kam-Biu Luk)

  32. Major Items of U.S. Project Scope • Muon tracking system (veto system) • Gd-loaded liquid scintillator • Calibration systems • PMT’s, base’s & control • Readout electronics & daq/trigger hardware (partial) • Acrylic vessels (antineutrino detector) • Detector integration activities • Project management activities P5 Review (Kam-Biu Luk)

  33. U.S. Project Scope & Budget Targets P5 Review (Kam-Biu Luk)

  34. Details of Additional U.S. Scope There are opportunities for the U.S. in other areas also: These are items for which additional U.S. collaborators could participate P5 Review (Kam-Biu Luk)

  35. Overall Project Schedule P5 Review (Kam-Biu Luk)

  36. Prelim. Civil Construction Sched. P5 Review (Kam-Biu Luk)

  37. Project Development • Schedule/activities over next several months: now – June now – summer now – Aug July – Nov Aug – Nov Determine scale of detector for sizing halls: Continue building strong U.S. team - key people: Conceptual design, scale & technology choices: Firm up U.S. scope, schedule & cost range: Write CDR, prepare for CD-1: P5 Review (Kam-Biu Luk)

  38. Funding Profile FY06 U.S. R&D $2M FY07 $3.5M FY08 U.S. Construction $8M FY09 $14M FY10 $8M Begin construction in China March 2007 CD-1 in U.S. November 2006 CD-2 in U.S. September 2007 Begin data collection January 2010 Measure sin2213 to 0.01 March 2013 P5 Review (Kam-Biu Luk)

  39. Synergy of Reactor and Accelerator Experiments 90% CL Reactor w 100t (3 yrs) + Nova Nova only (3yr + 3yr) Reactor w 10t (3yrs) + Nova Reactor experiments can help in Resolving the23 degeneracy (Example: sin2223 = 0.95 ± 0.01) Δm2 = 2.5×10-3 eV2sin2213 = 0.05 Reactor w 100t (3 yrs) +T2K T2K (5yr,n-only) Reactor w 10t (3 yrs) +T2K 90% CL 90% CL Reactor experiments provide a better determination of 13 McConnel & Shaevitz, hep-ex/0409028 P5 Review (Kam-Biu Luk)

  40. P5 Review (Kam-Biu Luk)

  41. ~1700 m Ling Ao Daya Bay P5 Review (Kam-Biu Luk)

  42. Sensitivity For 3 years With four 20-t modules at the far site and two 20-t modules at each near site: P5 Review (Kam-Biu Luk)

  43. P5 Review (Kam-Biu Luk)

  44. P5 Review (Kam-Biu Luk)

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