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Determining The Neutrino Mixing Angle  13 With The Daya Bay Nuclear Power Plants

Determining The Neutrino Mixing Angle  13 With The Daya Bay Nuclear Power Plants. Kam-Biu Luk University of California, Berkeley and Lawrence Berkeley National Laboratory Seminar at BNL, November 4, 2005. Neutrino Mixing. Inverted hierarchy. Normal hierarchy. m 3 2. m 2 2.  m 2 32.

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Determining The Neutrino Mixing Angle  13 With The Daya Bay Nuclear Power Plants

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  1. Determining The Neutrino Mixing Angle 13With The Daya Bay Nuclear Power Plants Kam-Biu Luk University of California, Berkeley and Lawrence Berkeley National Laboratory Seminar at BNL, November 4, 2005

  2. Neutrino Mixing Inverted hierarchy Normal hierarchy m32 m22 m232 m12 m22 m221 m32 m12 • For three generations of massive neutrino, the weak eigenstates are • not the same as the mass eigenstates: Pontecorvo-Maki- Nakagawa-Sakata Matrix • Parametrize the PMNS matrix as: Majorana phases solarnreactornatmosphericnneutrinoless reactornaccelerator LBL n accelerator LBL n double- decay Six parameters: 2 m2, 3 angles, 1 phase+ 2 Majorana phases Daya Bay Experiment

  3. Neutrino Oscillation • The probability ofne X disappearance is: • The probability ofnm neappearance is given by: Daya Bay Experiment

  4. Current Status of Mixing Parameters (23, m232) m232 =(2.4+0.4-0.3)10-3 eV2 23  45 m221 =(7.8+0.6-0.5)10-5 eV2 12 =(32+4-3) (13, m231) Dm231Dm232 >> Dm221 q12andq23are large (12, m221) Unknowns：sin2213， , sign of m232 Daya Bay Experiment

  5. Current Knowledge of 13 Sin2(213) < 0.18 Sin2(213) < 0.09 At m231 = 2.5103 eV2, sin22 < 0.15 Maltoni etal., New J. Phys. 6,122(04) Daya Bay Experiment

  6. Some Ideas For Measuring13 absorber decay pipe detector p target horn + + + • Method 1: Accelerator Experiments • appearance experiment: • need other mixing parameters to extract 13 • baseline O(100-1000 km), matter effects present • expensive • Method 2: Reactor Experiments • disappearance experiment: e  X • baseline O(1 km), no matter effects • • relative cheap Daya Bay Experiment

  7. 90% CL Reactor w 100t (3 yrs) + Nova Nova only (3yr + 3yr) Reactor w 10t (3yrs) + Nova Synergy of Reactor and Accelerator Experiments 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 Daya Bay Experiment

  8. Reactor e For 235U fission, for instance,  2 3 5 U n X X 2 n + + + 92 1 2 where X1 and X2 are stable nuclei e.g. e/MeV/fisson 1 4 0 Ce 94 Zr 58 yielding a total of 98 protons, whereas 235U has 92 protons. That is, on average, 6 neutrons must beta decay, giving 6 es(per ~200 MeV). 40 3 GWthgenerates 6 × 1020 ne per sec Daya Bay Experiment

  9. e  p  e+ + n (prompt)  + p  D + (2.2 MeV) (delayed by ~180 s) • + Gd  Gd* + ’s(sum = 8 MeV) (delayed by ~30 s) n m Detection of  in liquid scintillator:Inverse  Decay Time-, space- 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 Threshold of inverse  decay is about 1.8 MeV; thus only about 25% of the reactor eis usable. Daya Bay Experiment

  10. -42 Daya Bay Experiment

  11. How To Measure 13 With Reactor e? 1. Rate deficit: deviation from 1/r2 expectation 2. Spectral distortion Daya Bay Experiment

  12. 235U 239Pu 238U 241Pu 0 0.5 1 1.5 2 2.5 3 3.5 normalized flux times cross section (arbitrary units) 2 3 4 5 6 7 8 9 10 E (MeV) Time Variation of Fuel Composition Typically known to ~1% Daya Bay Experiment

  13. Uncertainty in ne Energy Spectrum Bugey3 Measurement Best calculation Gösgen Bugey3 Measurement first-principle calculation • Three ways to obtain the energy spectrum: • Direct measurement • First principle calculation • Sum up anti-neutrino spectra from 235U, 239Pu, 241Pu and 238U 235U, 239Pu, 241Pu from their measured b spectra 238U(10%) from calculation (10%) • Measurements agree with calculations to ~2% Daya Bay Experiment

  14. Background 12B 12N Keep everything as radioactively pure as possible! KamLAND Depends on the flux of cosmic muons in the vicinity of the detector Go as deep as possible! Daya Bay Experiment

  15. Location of Daya Bay • 45 km from • Shenzhen • 55 km from • Hong Kong Daya Bay Experiment

  16. The Site LingAo II NPP: 2  2.9 GWth Ready by 2010 Daya Bay NPP: 2  2.9 GWth LingAo NPP: 2  2.9 GWth Daya Bay Experiment

  17. 9. Hamaoka(Japan) (5) 0 2 4 6 8 10 12 14 16 18 20 22 24 26 GWth Ranking of Nuclear Power Plants 1. Kashiwazaki (Japan) (7) 2. Zaporozhye (Ukraine) (6) 3. Yonggwang(S. Korea) (6) 3. Ulchin(S. Korea) (6) 5. Gravelines (France) (6) 6. Paluel (France) (4) 6. Cattenom(France) (4) 8. Fukushima Daiichi(Japan) (6) 10. Ohi(Japan) (4) 11. Fukushima Daini(Japan) (4) 12. Daya Bay-Ling Ao(China) (4+2) ~2010 Daya Bay Experiment

  18. Horizontal Access Tunnels • Advantages of horizontal access tunnel: • - mature and relatively inexpensive technology • - flexible in choosing overburden • - relatively easy and cheap to add expt. halls • - easy access to underground experimental facilities • - easy to move detectors between different • locations with good environmental control. Daya Bay Experiment

  19. A ~1.5 km-long Tunnel Onsite Daya Bay Experiment

  20. Cross Section of Tunnel For Daya Bay Experiment 7.2 m 1.2 m 1.2 m 3.2 m 3.2 m 0.8 m Daya Bay Experiment

  21. Where To Place The Detectors ? Sin2(2q13) = 0.1 Dm231 = 2.5 x 10-3 eV2 Sin2(2q12) = 0.825 Dm221 = 8.2 x 10-5 eV2 ne far detector to measure changes at L2 reactor near detector to measure raw flux at L1 Daya Bay Experiment

  22. Where To Place The Detectors At Daya Bay? ~1700 m Ling Ao Daya Bay Daya Bay Experiment

  23. Possible Locations of Detector Sites Far site Empty detectors are moved to underground halls through an access tunnel with 8% slope. Filled detectors can be swapped between the underground halls via the 0%-slope tunnels. 570 m Ling Ao Near 1175 m Ling Ao-ll NPP (under const.) 590 m Ling Ao NPP Excess portal Daya Bay Near Daya Bay NPP Daya Bay Experiment

  24. Entrance portal Location of Tunnel Entrance Daya Bay Experiment

  25. Location of Daya Near Detector Daya Bay Experiment

  26. Location of Ling Ao Near Detector Daya Bay Experiment

  27. Location of Far Detector Daya Bay Experiment

  28. 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 Daya Bay Experiment

  29. 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 What Target Mass Should Be? Systematic error (per site): Black : 0.6% Red : 0.25% Blue : 0.12% Daya Bay Experiment

  30. 20t Gd-doped LS buffer gamma catcher Conceptual Design of Detector Modules • 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: 40 t Daya Bay Experiment

  31. ~350 m ~98 m ~208 m ~97 m Cosmic-ray Muon • Apply the Geiser parametrization for cosmic-ray flux at surface • Use MUSIC and mountain profile to estimate muon flux & energy near site far site Daya Bay Experiment

  32. Conceptual 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 strips or RPCs • Combined efficiency of Cherenkov and tracker > 99.5% PMTs Tracker detector module rock Daya Bay Experiment

  33. Alternative Design top of water pool 40t-3 layer module Daya Bay Experiment

  34. Background Inside Detector • Two classes of background: • Uncorrelated: • Accidental─ random coincidence of two unrelated events appear close in space and time. • 2.Correlated: • Fast neutron ─ a fast spallation neutron gets into the detector, creates a prompt signal (knock-out proton), thermalizes and is captured. • Cosmogenic isotopes─ 9Li and 8He with β-n decay modes are created in spallation of μ with 12C. The • decays mimic the antineutrino signal. Daya Bay Experiment

  35. -n Decay Of 8He And 9Li τ½ = 178 ms 49.5% Correlated τ½ = 119 ms 16% Correlated Correlated final state: β+n+2α Correlated final state: β+n+7Li Daya Bay Experiment

  36. Background 20t module • Use a modified Palo-Verde-Geant3-based MC to model response of detector. • 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. The above number is before shower-muon cut which can further reduce cosmogenic background. Daya Bay Experiment

  37. Detector Systematic Issues • Potential sources of systematic uncertainty are: • detector efficiency • gadolinium fraction (neutron detection efficiency) • target mass • target chemistry: fraction of free proton (target • particle) in terms of hydrogen/carbon • trigger efficiency • cut efficiency • live time • surprises at the 0.01 level Daya Bay Experiment

  38. Possible Solutions • Relative detector efficiency • Calibrate all detectors with the same set of • radioactive sources. • Gd fraction • (i) Control synthesis of liquid scintillator • (ii) Measure the Gd- to H-capture ratio • Target mass • (i) Use the same batch or equally splitting batches • of liquid scintillator, and measure flow rates • (ii) Use eevents to cross calibrate, implying moving • detectors. Daya Bay Experiment

  39. Detector Systematic Uncertainties 0.25% 0.1 0.1 0.1 relative measurement absolute measurements per module Daya Bay Experiment

  40. Geotechnical Survey • Topography survey: Completed • Geological Survey: Completed • Verified topographic information • Generated new map covering 7.5 km2 • Geological Physical Survey: Completed • High-resolution electric resistance • Seismic • Micro-gravity • Bore-Hole Drilling: November-December, 2005 raw data Daya Bay Experiment

  41. Far site 1600 m from Lingao 1900 m from Daya Overburden: 350 m Ling Ao Near 500 m from Lingao Overburden: 98 m Mid site ~1000 m from Daya Overburden: 208 m Ling Ao-ll NPP (under const.) 672 m (12% slope) Ling Ao NPP 8% slope Daya Bay Near 360 m from Daya Bay Overburden: 97 m Daya Bay NPP Total length: ~3200 m Daya Bay Experiment

  42. Sensitivity of sin2213 • Daya Bay site - baseline = 360 m - target mass = 40 ton - B/S = ~0.5% • LingAo site - baseline = 500 m - target mass = 40 ton - B/S = ~0.5% • Far site - baseline = 1900 m to DYB cores 1600 m to LA cores - target mass = 80 ton - B/S = ~0.2% • Three-year run (0.2% statistical error) • Detector residual error = 0.2% • Use rate and spectral shape 90% confidence level 2 near + far near (40t) + mid (40 t) 1 year Sept, 2005 Daya Bay Experiment

  43. sin2213 = 0.02 sin2213 = 0.1 Precision of m231 Daya Bay Experiment

  44. Gd-loaded Liquid Scintillator • It can significantly reduce backgrounds (short capture time, high capture energy) • Problems: (a) doping Gd into organic LS from inorganic Gd compound and achieve Light yield =55% of anthracene Att. length = 11m (b) Aging Palo Verde: 0.03%/day Chooz: 0.4%/day Daya Bay Experiment

  45. Synthesis of Gd-loaded Liquid Scintillator • Investigating a few candidates at IHEP: One candidate: - 0.1% Gd (D2EHP-ligand) in 20% mesitylene-80% dodecane • Light yield: 91% of pure LS • attenuation length = 6.2 m • stable for more than two months: - no effect on acrylic • R&D collaborative effort at BNL: • - Gd (carboxylate ligands) in PC and • dodecane • - all stable for almost a year Daya Bay Experiment

  46. Prototype Detector at IHEP • Constructing a 2-layer prototype with • 0.5 t Gd-doped LS enclosed in 5 t of • mineral oil, and 45 8” PMTs to evaluate • design issues at IHEP, Beijing PMT mount Steel tank Front-end board (version 2) acrylic vessel Daya Bay Experiment

  47. The Aberdeen Tunnel Experiment • Study cosmic muons & cosmogenic background in Aberdeen Tunnel, Hong Kong. Overburden ~ Daya Bay sites similar geology between Aberdeen and Daya Bay Installing proptubes in Sept, 2005 Daya Bay Experiment

  48. Precision Measurement of 12 and m221 Daya Bay Experiment

  49. Precise Measurement of 12 • Since reactor eare low-energy, it is a disappearance experiment: Large-amplitude oscillation at ~55 km due to 12 • Near detectors close to • reactors 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 • of 12 KamLAND Sin2(2q13) = 0.1 Dm231 = 2.5 x 10-3 eV2 Sin2(2q12) = 0.825 Dm221 = 8.2 x 10-5 eV2 Daya Bay Experiment

  50. Location of Hong Kong Site For 12 Measurement Daya Bay NPP ~55 km Shenzhen Tai Mo Shan (957 m) Hong Kong Daya Bay Experiment

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