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Comparison of Reactor Sites and q 13 Experiments Karsten Heeger LBNL

Comparison of Reactor Sites and q 13 Experiments Karsten Heeger LBNL. 1-2 km. nuclear reactor. Braidwood. Diablo Canyon. Daya Bay. Reactor Sites in the US. Diablo Canyon. Daya Bay. Chooz, France. ‘ Double-Chooz’ Project 10-20 tons detectors 8.4 GW th reactor power

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Comparison of Reactor Sites and q 13 Experiments Karsten Heeger LBNL

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  1. Comparison of Reactor Sites and q13 ExperimentsKarsten HeegerLBNL US Reactor q13 Meeting, March 15, 2004

  2. 1-2 km nuclear reactor Braidwood Diablo Canyon Daya Bay Reactor Sites in the US Diablo Canyon Daya Bay US Reactor q13 Meeting, March 15, 2004

  3. Chooz, France ‘Double-Chooz’ Project 10-20 tons detectors 8.4 GWth reactor power 300 mwe overburden at far site 50 mwe overburden at near site 0.1-0.2 km 1.05 km ‘Double-Chooz’ Sensitivity sin2(213) < 0.03 at 90% CL after 3 yrs, matm2 = 2 x 10-3 eV2 US Reactor q13 Meeting, March 15, 2004

  4. Future Constraints on 13 let’s assume that Double-Chooz will be funded US Reactor q13 Meeting, March 15, 2004 Upper limits correspond to 90% C.L.

  5. A Second q13 Reactor Neutrino Oscillation Experiment? What experiment do we need to exploit the full physics potential? Can we improve on Double-Chooz? General Strategies • two larger detectors in optimal location. • eliminate dependence on reactor flux calculation • need to understand relative acceptance of two detectors rather than absolute acceptance of a single detector. Issues Relevant for Evaluating Experiments • reactor power • baseline • detector size (fiducial volume) - signal statistics - muon deadtime • background • relative uncertainty on acceptance • relative uncertainty on energy scale and linearity US Reactor q13 Meeting, March 15, 2004

  6. Different q13 Experiments • Scales of Experiments and Sensitivities • small: sin22q13~0.04 •  goal to make a fast discovery of q13 if just below the current Chooz limit. Entirely based on rate. • medium: sin22q13~0.01 •  make a discovery of q13 and determine if CP violation in lepton sector is observable..Resolve mass hierarchy together with long baseline experiments. Complementary to J-PARC nu and off-axis experiments. • Note: Experimental challenges to obtain sin22q13 < 0.01are difficult. • large: sin22q13~?What might the ultimate experiment look like? • Most precise measurement of q13. What are the possible strategies to reach these sensitivities? US Reactor q13 Meeting, March 15, 2004

  7. 3  Sensitivity to sin2(213) Minos Reactor Exp NuMI Off-Axis sin2(213) Reactor & Long Baseline Experiments Measuring sin2(213) Chooz 90% CL sin2(213) ≤ 0.14 Minos 3- sensitivity sin2(213) = 0.07 13Reactor Exp sin2(213) < 0.01-0.02 90% CL NuMI Off-Axis 3- sens. sin2(213) < 0.007 at matm2 = 2.5 x 10-3 eV2 reactor 90% CL= 0.01 and (sin2(213)) = 0.006 Ref: NuMI Off-Axis Collaboration, Progress Report 12/2003 US Reactor q13 Meeting, March 15, 2004

  8. sin2(213) vs P(e) for P(e)=0.02   eappearance sin2(213) reactor 90% CL= 0.01 and (sin2(213)) = 0.006 Reactor & Long Baseline Experiments Determining Mass Hierarchy Ref: NuMI Off-Axis Collaboration, Progress Report 12/2003 US Reactor q13 Meeting, March 15, 2004

  9. Diablo Canyon Daya Bay Kashiwazaki Braidwood < 700 mwe < 450 mwe ~300 mwe How do you choose a reactor site? Some General Criteria • Reactor Power • Baseline • Detector Size • Overburden  Detector design and systematics will determine sin2213 sensitivity. Some sites place significant constraints on baseline and detector size: Choozhorizontal tunnel sites2 vertical shafts US Reactor q13 Meeting, March 15, 2004

  10. Issues and Questions Overburden & Backgrounds 1. What are the minimum overburden requirements for near and far detector? Overburden requirements as a function of 2. What do we gain from having the same overburden at near and far detector? Baseline & Physics 3. Baseline and physics potential - distance - power - size - muon veto efficiency US Reactor q13 Meeting, March 15, 2004

  11. Constructing a Figure of Merit Signal Backgrounds I) Limit absolute background contribution to < 1% II) Measure backgrounds to < 1% and subtract US Reactor q13 Meeting, March 15, 2004

  12. Can we measure backgrounds? Measure background spectrum correlated with muon flux and neutron background high muon veto efficiency stability background statistics II) Direct measurement during reactor refueling time: 3-4 weeks every 12-18 months 4-8% time for background measurement An optimistic estimate No of Reactors B/S 2 4.15/S  0.013 for 100k events 3 6/S 4 7.8/S US Reactor q13 Meeting, March 15, 2004

  13. Constructing a Figure of Merit Deadtime Due to Spallation Cuts Oscillation Effect US Reactor q13 Meeting, March 15, 2004

  14. Detector Size Statistical Error stat ~ 0.5%forL= 300t-yr Nominal data taking: 3 years (?) Interaction rate: 300 /yr/ton at 1.8 km Fiducial volume > 30 ton at 1.8 km Detector Event Rate/Year ~250,000 ~60,000 ~10,000 US Reactor q13 Meeting, March 15, 2004

  15. Overburden Choozcandidate events reactor on 2991 reactor off 287 Chooz has 9.5% irreducible background, presumably - fast neutrons, and - spallation backgrounds. Minimum overburden scaling Chooz background with muon spectrum that generates spallation backgrounds bkgd depth (mwe) 10% 300 < 5% > 400 < 2% > 560 < 1% > 730 US Reactor q13 Meeting, March 15, 2004

  16. Muon Veto and Efficiency Chooz have 98% (?) > 99.5% possible (?) event candidates reactor on 2991 reactor off 287 Improvement in muon veto can reduce backgrounds. bkgd muon veto efficiency 10% 98% 2% 99.5% < 0.5% 99.9% Note: Double-Chooz expects to have ~ 50% muon-related deadtime in near detector. Understanding muon veto efficiency and stability is critical. US Reactor q13 Meeting, March 15, 2004

  17. 100 t 50 t 25 t Muon Flux and Deadtime Muon veto requirements increase with volume, reduce with depth Chooz 2% deadtime • For a target of > 50 t perhaps we may want modular detectors (maybe 2 x 25 t detectors)? • Small dependence on shape of detector. US Reactor q13 Meeting, March 15, 2004

  18. measured oscillation Oscillation Effect Baseline and Physics Sensitivity measured osc max osc max oscillation US Reactor q13 Meeting, March 15, 2004

  19. Requirements for Near and Far Detector Near Detector measurement of backgrounds non-trivial dead time may be significant signal/background critical (> 100) Far Detector signal/background important (> 100) baseline and oscillation sensitivity include dead time US Reactor q13 Meeting, March 15, 2004

  20. Reactor Power Thermal Reactor Power US Reactor q13 Meeting, March 15, 2004

  21. Baselines Baselines Near Far ? US Reactor q13 Meeting, March 15, 2004

  22. Site Comparison Far Detector Performance with and without Oscillation Effect w/out oscillation w/ oscillation US Reactor q13 Meeting, March 15, 2004

  23. US Reactor q13 Meeting, March 15, 2004

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