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

April 18, 2006P5 Review (Kam-Biu Luk)2 ?  13  The Last Unknown Neutrino Mixing Angle  23    45  U MNSP Matrix Maki, Nakagawa, Sakata, Pontecorvo What is  e fraction of 3 ? U e3 is a gateway to CP violation in neutrinos: ? atmospheric, Accelerator Reactor, accelerator 0  SNO, solar SK, KamLAND  12 ~ 32°  23 = ~ 45°  13 = ? P(   e ) - P(     e )  sin(2  12 )sin(2  23 )cos 2 (  13 )sin(2  13 )sin 

April 18, 2006P5 Review (Kam-Biu Luk)3 Current Knowledge of  13 Direct search At  m 2 31 = 2.5  10  3 eV 2, sin 2 2   < 0.15 allowed region Experimental allowed at 3  Number of predictions Theoretical predications

April 18, 2006P5 Review (Kam-Biu Luk)4 Recommendations APS Neutrino Study Group: Neutrino Scientific Assessment Group:

April 18, 2006P5 Review (Kam-Biu Luk)5 Limitations of Past and Current Reactor 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%)

April 18, 2006P5 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

April 18, 2006P5 Review (Kam-Biu Luk)7 Goals And Approach Utilize the Daya Bay nuclear power facilities to: - determine sin 2 2  13 with a sensitivity of 1% - measure  m 2 31 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.

April 18, 2006P5 Review (Kam-Biu Luk)8 Where To Place The Detectors ? Large-amplitude oscillation due to  12 Small-amplitude oscillation due to  13 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 Sin 2 (   ) = 0.1  m 2 31 = 2.5 x eV 2 Sin 2 (   ) =  m 2 21 = 8.2 x eV 2 Since reactor  e are low-energy, it is a disappearance experiment:

April 18, 2006P5 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) Time- and energy-tagged signal is a good tool to suppress background events. Energy of  e is given by: E   T e+ + T n + (m n - m p ) + m e+  T e MeV keV The reaction is the inverse  -decay in Gd-doped liquid scintillator: Arbitrary Flux Cross Section Observable Spectrum From Bemporad, Gratta and Vogel 0.3b 50,000b

April 18, 2006P5 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

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April 18, 2006P5 Review (Kam-Biu Luk)12 Ling Ao II NPP: 2  2.9 GW th Ready by Ling Ao NPP: 2  2.9 GW th 55 km 45 km The Daya Bay Nuclear Power Facilities Daya Bay NPP: 2  2.9 GW th 1 GW th generates 2 ×  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

April 18, 2006P5 Review (Kam-Biu Luk)13 Daya Bay NPP Ling Ao NPP Ling Ao-ll NPP (under const.) Entrance portal Empty detectors: moved to underground halls through access tunnel. Filled detectors: swapped between underground halls via horizontal tunnels. Total length: ~2700 m 230 m (15% slope) 290 m (8% slope) 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 Mid site ~1000 m from Daya Overburden: 208 m

April 18, 2006P5 Review (Kam-Biu Luk)14 A Versatile Site Rapid deployment: - Daya near site + mid site - 0.7% reactor systematic error 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

April 18, 2006P5 Review (Kam-Biu Luk)15 Geotechnical Survey far Daya near Lingao near mid Topological survey: Length: 2.5 km (S-N) Width: 450 m ~ 1.3 km (E-W) Area: km 2 Scale: Along tunnel 1:2000 Portal area 1:500 Topological survey - complete Geophysical survey - complete Bore drilling - complete

April 18, 2006P5 Review (Kam-Biu Luk)16 Planned tunnel fault Lingao near Daya near mid far Weathering bursa Geophysical Survey Electrical Resistivity method mid Lingao near

April 18, 2006P5 Review (Kam-Biu Luk)17 bursa Bore Drilling Location Drill Depth (m) ZK1211 ZK2210 Zk3127 Zk4133

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April 18, 2006P5 Review (Kam-Biu Luk)19 (in the weathering bursa)

April 18, 2006P5 Review (Kam-Biu Luk)20 Findings of 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 Pat Dobson (LBL) Chris Laughton (FNAL) Joe Wang (LBL) Yanjun Sheng (IGG) U.S. experts in geology and tunnel construction assist geotechnical survey:

April 18, 2006P5 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

April 18, 2006P5 Review (Kam-Biu Luk)22 ~350 m ~97 m ~98 m ~210 m Cosmic-ray Muon Apply modified Geiser parametrization for cosmic-ray flux at surface Use MUSIC and mountain profile to estimate muon flux & energy DYBLAMidFar Elevation (m) Flux (Hz/m 2 ) Mean Energy (GeV)

April 18, 2006P5 Review (Kam-Biu Luk)23 What Target Mass Should Be? Systematic error (per site): Black : 0.6% Red : 0.25% Blue : 0.12% Solid lines : near+far Dashed lines : mid+far DYB: B/S = 0.5% LA: B/S = 0.4% Mid: B/S = 0.1% Far: B/S = 0.1%  m 2 31 = 2  eV 2 tonnes

April 18, 2006P5 Review (Kam-Biu Luk)24 Design of Antineutrino Detectors Three-layer structure: 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: buffer 20t Gd-doped LS gamma catcher Isotopes Purity (ppb) 20cm (Hz) 25cm (Hz) 30cm (Hz) 40cm (Hz) 238 U(>1MeV) Th(>1MeV) K(>1MeV) Total Oil buffer thickness

April 18, 2006P5 Review (Kam-Biu Luk)25 3 zone cut Why three zones ? Three zones: - Construction of acrylic vessels is more involved - More  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% 2 zone cut – Using 4 MeV cut can reduce the error by a factor of two, but backgrounds from  do not allow us to do so CHOOZ

April 18, 2006P5 Review (Kam-Biu Luk)26 Design of Shield-Muon Veto 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% 2m of water ~0.05 Neutron background vs thickness of water

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April 18, 2006P5 Review (Kam-Biu Luk)28 Background Near SiteFar Site Radioactivity (Hz)<50 Accidental B/S<0.05% Fast neutron background B/S0.15%0.1% 8 He/ 9 Li B/S0.55%0.25% 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: 8 He/ 9 Li 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: The above number is before shower-muon cut. 20t module

April 18, 2006P5 Review (Kam-Biu Luk)29 Systematic Uncertainty Systematic errorChoozDaya Bay Reaction Cross Section1.9% 0, near-far cancellation Energy released per fission0.6% 0, near-far cancellation Reactor Power0.7%0.06%, near-far cancellation Number of Protons0.8%0, detector swapping Detection efficiency*1.5%~0.2%, fewer cuts, detector swapping Total2.75%~0.2% Statistical Error (3 years): 0.2% Residual systematic error: ~ 0.2% * 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.

April 18, 2006P5 Review (Kam-Biu Luk)30 Daya Bay siteDaya Bay site - baseline = 360 m - baseline = 360 m - target mass = 40 tonne - target mass = 40 tonne - B/S = ~0.5% - B/S = ~0.5% LingAo siteLingAo site - baseline = 500 m - baseline = 500 m - target mass = 40 tonne - target mass = 40 tonne - B/S = ~0.5% - B/S = ~0.5% Far siteFar site - baseline = 1900 m to DYB cores - baseline = 1900 m to DYB cores 1600 m to LA cores 1600 m to LA cores - target mass = 80 tonne - target mass = 80 tonne - B/S = ~0.2% - B/S = ~0.2% Three-year run (0.2% statistical error)Three-year run (0.2% statistical error) Detector residual error = 0.2%Detector residual error = 0.2% Use rate and spectral shapeUse rate and spectral shape 90% confidence level Sensitivity of sin 2 2  13 2 near + far near (40t) + mid (40 t) 1 year Near-mid

April 18, 2006P5 Review (Kam-Biu Luk)31 Precision of  m 2 31 sin 2 2  13 = 0.02 sin 2 2  13 = 0.1

April 18, 2006P5 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

April 18, 2006P5 Review (Kam-Biu Luk)33 U.S. Project Scope & Budget Targets

April 18, 2006P5 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

April 18, 2006P5 Review (Kam-Biu Luk)35 Overall Project Schedule

April 18, 2006P5 Review (Kam-Biu Luk)36 Prelim. Civil Construction Sched.

April 18, 2006P5 Review (Kam-Biu Luk)37 Project Development Schedule/activities over next several months: 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: now – June now – summer now – Aug July – Nov Aug – Nov

April 18, 2006P5 Review (Kam-Biu Luk)38 Funding Profile Begin construction in ChinaMarch 2007 CD-1 in U.S.November 2006 CD-2 in U.S.September 2007 Begin data collection January 2010 Measure sin 2 2  13 to 0.01March 2013 FY06U.S. R&D $2M FY07 $3.5M FY08U.S. Construction $8M FY09 $14M FY10 $8M

April 18, 2006P5 Review (Kam-Biu Luk)39 Synergy of Reactor and Accelerator Experiments Δ m 2 = 2.5×10 -3 eV 2 sin 2 2  13 = 0.05 Reactor experiments can help in Resolving the  23 degeneracy (Example: sin 2 2  23 = 0.95 ± 0.01) 90% CL Reactor w 100t (3 yrs) + Nova Nova only (3yr + 3yr) Reactor w 10t (3yrs) + Nova 90% CL McConnel & Shaevitz, hep-ex/ % CL Reactor w 100t (3 yrs) +T2K T2K (5yr, -only) Reactor w 10t (3 yrs) +T2K Reactor experiments provide a better determination of  13

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April 18, 2006P5 Review (Kam-Biu Luk)41 Daya Bay Ling Ao~1700 m

April 18, 2006P5 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:

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