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NEUTRINO OSCILLATION MEASUREMENTS WITH REACTORS

NEUTRINO OSCILLATION MEASUREMENTS WITH REACTORS. R. D. McKeown Caltech. NDM09 Madison, Wisconsin Sept. 4, 2009. Outline. Reactor antineutrinos – generation, detection KamLAND experiment and results Reactor q 13 experiments Conclusions. Neutrino Studies with Nuclear Reactors.

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NEUTRINO OSCILLATION MEASUREMENTS WITH REACTORS

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  1. NEUTRINO OSCILLATION MEASUREMENTS WITH REACTORS R. D. McKeown Caltech NDM09 Madison, Wisconsin Sept. 4, 2009

  2. Outline • Reactor antineutrinos – generation, detection • KamLAND experiment and results • Reactor q13 experiments • Conclusions

  3. Neutrino Studies with Nuclear Reactors • ne from n-rich fission products • detection via inverse beta decay (ne+pge++n) • Measure flux and energy spectrum

  4. Discovery of the Neutrino – 1956 "All you have to do is imagine something that does practically nothing. You can use your son-in-law as a prototype." F. Reines, Nobel Lecture, 1995

  5. g 2.2 MeV d p n + e g g 511keV 511keV Detection Signal n + p g n + e+ Coincidence signal: • Prompt: e+ annihilation g En=Eprompt+En+0.8 MeV • Delayed: n+p180 ms capture time, 2.2 MeV • n+Gd 30 ms capture time, 8 MeV

  6. The Reactor Neutrino Flux and Spectrum Reactor Isotopes ~ 200 MeV per fission ~ 6 e per fission ~ 2 x 1020e/GWth-sec • 235U, 239Pu, 241Pu from b measurements • 238U calculated • Time dependence due to fuel cycle

  7. Reactors are calibrated sources of n ’s !! Precise Measurements Flux and Energy Spectrum g ~1-2 %

  8. The Motivation for KamLAND • Persistent observations of deficit of solar neutrinos • 1998 – observation of oscillations of atmospheric neutrinos by Super-K • Unique opportunity to perform longer baseline reactor experiment in Japan

  9. Enter • Long Baseline (180 km) • Calibrated source(s) • Large detector (1 kton) • Deep underground (2700 mwe)

  10. Kashiwazaki Takahama Ohi KamLAND uses the entire Japanese nuclear power industry as a long­baseline source Note: The neutrinos are free of charge!

  11. Energy Spectrum

  12. KamLAND Result (2008) arXiv:0801.4589v2 [hep-ex] Best combined fit values: Dm2 = 7.59+0.21-0.21 x 10-5 eV2 tan2q = 0.47+0.06-0.05

  13. Maki – Nakagawa – Sakata Matrix Gateway to CP Violation! CP violation

  14. CHOOZ/Palo Verde limits for 13 Allowed region At m231 = 2.5  103 eV2, sin22 < 0.15

  15. Hints from Global Fits Fogli, et al., arXiv:0905:3549 Also: A. B. Balantekin and D. Yilmaz, J. Phys. G 35, 075007 (2008) → sin22q13~ 0.06-0.08?

  16. ne Survival Probability Dominant 12Oscillation Subdominant 13 Oscillation • “Clean” measurements of q, Dm2 • No CP violation • Negligible matter effects

  17. Reactor θ13 Neutrino Experiments Chooz, France RENO, Korea Daya Bay, China Angra, Brazil Under construction. Proposed and R&D.

  18. Two identical detectors:10 tons each. Phase 1 (2010): Far Detector in existing lab. Phase 2 (2011-12): running with Near detector in new lab. 1051 m 380 m • Status(July09): • PMT’s installed at far site • Acrylic vessels constructed • Veto under construction

  19. Near Detector Tunnel Length 100 m 70 m Hill Tunnel Length 300 m 1.4 km 200 m Mt. Far Detector http://www.awa.tohoku.ac.jp/taup2007/slides/workshop14/roomA/05-RENO-TAUP07.ppt

  20. Comparison Table

  21. Daya Bay Nuclear Power Plant • 4 reactor cores, 11.6 GW • 2 more cores in 2011, 5.8 GW • Mountains provide overburden to shield cosmic-ray backgrounds • Baseline ~2km • Multiple detectors → measure ratio

  22. Experiment Layout • Multiple detectors • per site cross-check • detector efficiency • Two near sites • sample flux from • reactor groups 20T Total Tunnel length ~ 3000 m

  23. Antineutrino Detector Calibration units 20 T Gd-doped liquid scintillator 192 8” PMT’s Gamma catcher Buffer oil • 3 zone design • Uniform response • No position cut • 12%/√ E resolution Acrylic Vessels SS Tank

  24. Muon Veto System RPC’s Water Cerenkov (2 layers) Redundant veto system → 99.5% efficient muon rejection

  25. Site Preparation Daya Bay Near Hall construction (100m underground) Assembly Building Tunnel lining Portal of Tunnel

  26. Civil Construction Status Far Hall Ling Ao Hall Tunnel Entrance Daya Bay Near Hall Construction Tunnel

  27. Hardware Progress SSV Prototype 4m Acrylic Vessel Prototype Transporter Calibration Units

  28. Detector Assembly Delivery of 4m AV SS Tank delivery Clean Room

  29. Sensitivity to Sin22q13 • Experiment construction: 2008-2011 • Start acquiring data: 2011 • 3 years running

  30. Project Schedule • October 2007: Ground breaking • August 2008: CD3 review (DOE start of construction) • March 2009:Surface Assembly Building occupancy • Summer 2009: Daya Bay Near Hall occupancy • Fall 2009: First AD complete • Summer 2010: Daya Bay Near Hall ready for data • Summer 2011: Far Hall ready for data (3 years of data taking to reach goal sensitivity)

  31. Conclusions • Reactor neutrino experiments have entered “precision era” • KamLAND provided the first “laboratory” evidence for neutrino oscillations, with a high precision measurement of Dm122 • RENO, Double-CHOOZ, Daya Bay will study q13 during 2010-14, with Daya Bay reaching sin22q13<0.01 • If reactor experiments establish θ13 to be sufficiently large, Nova may then contribute unique sensitivity to the mass hierarchy in the next decade. In addition, the value of θ13 will provide necessary guidance to future accelerator-based long baseline experiments.

  32. Stay Tuned !!

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