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The Double Chooz Experiment

The Double Chooz Experiment conducted under the U.S. Department of Energy aimed to study neutrinos and their properties, facing technological challenges. Reines and Cowan's early neutrino detection led to advancements in understanding neutrino mixing. The experiment addressed questions on neutrino CP violation and mass ordering through innovative methodologies. Double Chooz's enhanced design and setup allowed for improved data collection and accuracy, surpassing the original Chooz experiment. The collaboration's international team of scientists brought expertise from various countries, aiming to achieve groundbreaking results in neutrino physics.

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The Double Chooz Experiment

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  1. q 13 The Double Chooz Experiment This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48. UCRL-Pres-221620 R.Svoboda

  2. the goals • the experiment • the people • the technological challenges • the status R.Svoboda

  3. 1956: Reines and Cowan detect neutrinos coming from the core of a nuclear reactor 1962: multiple types Nothing more until 1990’s mass and oscillations First change in Standard Model in 20 years Neutrino Physics n! R.Svoboda

  4. Neutrino Mixing atmospheric solar sij = sinqij cij = cosqij R.Svoboda

  5. We now have numbers to put in! q12= 30o q23= 45o ( 0.9 0.5 s13eid -0.35-0.6s13eid0.6-0.35s13eid 0.7 0.35-0.6s13eid -0.6-0.35s13eid 0.7 ) a …but d unknown ( ) q13 <13o 0.9 0.5 s13eid -0.35 0.6 0.7 0.35 -0.6 0.7 a Ue3 is 100% sensitive to the mixing angle θ13

  6. but we don’t know the mass ordering Don’sviolateCP?Isq13non-zero? Can use an accelerator nmbeam, But there are complications… R.Svoboda

  7. ne appearance in a nmbeam P(nmgne) = (2c13s13s23)2 sin2F31 +8c13s12s13s23(c12c23cosd-s12s13s23)cosF32sinF31sinF21 -8c13c12c23s12 s13s23sind sinF32sinF31 sinF21 +4s12c13(c12c23+s12s23s13-2c12c23s12s23s13cosd)sin2F21 -8c13s13s23(1-2s13 )(aL/4E)cosF32sinF31 2 lCPviolating 2 2 2 2 2 2 2 2 2 2 2 2 a = constant X neE CP:ag-a,dg-d R.Svoboda

  8. T2K Experiment in Japan (2009) Exist approved Kamioka ~1GeV n beam JAERI (Tokaimura) Super-K: 22.5 kt Hyper-K: 1000 kt 0.77MW 50 GeV PS 4MW 50 GeV PS Phase-I (0.77MW + Super-K) Phase-II (4MW+Hyper-K) ~ Phase-I  200

  9. Existing NuMI beam Off-axis to reduce energy ~$200M (phase 1) possible FNAL upgrade with new proton driver later possible second off-axis detector NOnA Experiment in US (20xx) R.Svoboda

  10. How well can they resolve the mass ordering problem? Phase 1 has no chance of even 2s if sin22q13 < 0.025 Billion $ upgrade R.Svoboda

  11. What about CP? Hopeless without beam upgrade Even with beam upgrade chance <15% If sin22q13 < 0.025 R.Svoboda

  12. It would be great to know ASAP if the value of q13is large or small R.Svoboda

  13. Prediction Not Much Theoretical Guidance • 27 models predications • 17 above 0.03 • 4 between 0.01 and 0.03 Double-Chooz 3y sensitivity R.Svoboda

  14. Chooz Best direct result is from Chooz R = 1.01  2.8%(stat)2.7%(syst) Sin2q13 < 0.19 An experiment designed to do something else Only ran 197 days with reactors at reduced power R.Svoboda

  15. Improving Chooz: Double Chooz 90 mwe 300 mwe • Rates include all expected efficiencies and reactor duty cycle • Far detector collects data at almost four times the rate of the original Chooz experiment, which ran for only 197 days. • Type N4 represents the highest neutrino flux one can get using only two cores D2 = 1,050 m D1 = 270 m 8.54GWth ChoozB Neardetector Fardetector 43 evt/day 425 evt/day R.Svoboda

  16. “One has to admire a country like France where there are two only kinds of reactors and a hundred different kinds of cheese. In the United States, it is just the opposite.” DOE Sec. Samuel Bodman during recent visit to France R.Svoboda

  17. systematics Error type CHOOZ Future Experiment 2 identical detector Low background Reactor Flux, cross section 1.9% - O(0.1%) Thermal power 0.7% - O(0.1%) E/Fission 0.6% - O(0.1%)  2.1% - O(0.1%) Why “Double”? Reactor induced systematics 2 detectors  cancellation of the reactor physical uncertainties R.Svoboda

  18. Reactor-Induced Systematics Distance ratio exactly cancels reactor thermal power uncertainty. This is not possible with more than two cores. 1114.6m 997.9m 260.3m Uncertainty due to solid angle is 0.06% 290.7m R.Svoboda

  19. Other Reactor Uncertainties • Effects of finite core size 0.01% (single detector) • fission barycenter (single detector) 0.03% • spent fuel ponds Type N4 reactors refuel every 8 months with 25% of fuel assemblies replaced. Spent fuel ponds have been accumulating for nine years. Uncertainty In long-lived fission products can be as high as 20% Initial estimate on uncertainty due to spent fuel is <0.1%. Still being studied to get actual number.

  20. One big improvement - Just run longer! @CHOOZ: R = 1.01  2.8%(stat)2.7%(syst) • Luminosity increase L = t x P(GW) x Vtarget R.Svoboda

  21. Who we are • group of ~100 scientists from 8 countries • France, U.S., Germany, Spain, Russia, Italy, Brazil*, U.K.* • Very Experienced: Chooz, Bugey, KamLAND, Super-Kamiokande, SNO June, 2006 * Have applied for membership

  22. Expected Sensitivity 2007-2012 • Far Detector starts 2008 • Near detector follows 16 months later • Double Chooz can surpass the original Chooz bound in 3 months • 90% C.L. contour if sin2(213)=0 • m2atm = 2.4 10-3 eV2 • m2atm = 2.8 10-3 eV2 Will be known to 10% by MINOS  R.Svoboda

  23. The Site R.Svoboda

  24. R.Svoboda

  25. Chooz-far Chooz-near Double-Chooz: 3 important sites … R.Svoboda

  26. Far Lab: Now Open for Business 300 m.w.e. Well measured backgrounds Now occupied by collaboration Old Chooz detector tank removal happening now R.Svoboda

  27. Near Lab Location is Optimized Rate Shape R.Svoboda

  28. R.Svoboda

  29. Near Lab (80 m.w.e) 30 meters 45 meters 7 meters Compared to 2004 LOI, Background factor of 3 less

  30. Engineering by EdF Will use explosives and sprayed concrete Costs well within budget (by factor of two) Construction to start next year Status R.Svoboda

  31. The Detectors Improved from design Of Chooz 534 8” PMTs 7% @ 1 MeV R.Svoboda

  32. target:80% dodecane + 20% PXE + 0.1% Gd g-catcher: ~60% dodecane + 10% PXE +30% mineral oil 511 keV 511 keV Non-scintillating buffer: mineral oil e+ e p Gd n PMTs supporting structure E ~ 8 MeV Muon VETO: scintillating oil Shielding: 17 cm steel Detector Design outer veto: prop tube array 7 m 7 m TwoIdenticalDetectors R.Svoboda

  33. Technological Challenge: Identical Detectors R.Svoboda

  34. What is the State of the Art? • Chooz had a 1.6% absolute detector systematic uncertainty, the best to date. Total uncertainty 2.7% • Bugey is the only experiment that has tried to build identical detectors. Result was 2.0% relative error. 5.0% total. • DoubleChoozgoal is 0.6% relative uncertainty. R.Svoboda

  35. How we will do this • We will use a physical tank for the fiducial volume instead of fitted vertex, unlike KamLAND, which has 4.7% uncertainty doing this (before 4p system) • We will control detector temperature at Near and Far Detector with active heating. • We will remix scintillator when starting Near Detector, or else throwaway first batch. • We will control the magnetic field inside detector and have developed a way to demagnetize the steel components. All PMT’s will have individual mumetal shields. Expensive, but thisisaseriousproblem. R.Svoboda

  36. X axis Y axis R.Svoboda

  37. PMT sensitivity w.r.t earth’s B field

  38. Mu-metal dark box (PMT Y axis)Also: Our measurments and Hamamatsu’sboth show significant tube to tube variation Difference (West – North) Black – Y axis pointing West Blue – Y axis pointing North Specification: <50 mG R.Svoboda

  39. …and • We have developed andtested two independent systems to measure the mass of target poured into each detector (0.2%) • We have considered variation of g, effects of finite size core and detector on distance (<0.1%) • We have considered effects of different depth for Near and Far (<0.1%) • New 162-page DC Document to be released this month gives quantitative details on all these topics. • Why not SWAP DETECTORS? R.Svoboda

  40. Technological Challenge: Swapping Detectors R.Svoboda

  41. SRP experiment 2 positions, 24 and 18 m detector on wheels – can be rolled 6 meters over smooth floor 18 meters, 24 meters, then back to 18 meters This has been tried Result:2.5 ± 1.1% change! R.Svoboda

  42. Why we think swapping will not be effective for us • Detector geometry needs to be kept constant at the level of a few mm • Reactor signal will not be the same • Swapped detectors can’t be swapped in time • Calibration is the most effective way to compare swapped detectors • …so better to leave them alone and concentrate on swappingcalibrationsystems, which can be done easily, cheaply, and at the same time • Also work on thing most likely to change: scintillator, PMTs, magnetic fields R.Svoboda

  43. Technological Challege: Scintillator R.Svoboda

  44. R-COO- 3+Gd R-COO- (R-COOH)x -OOC-R Gd doped scintillator • Solvant: 20% PXE – 80% Dodecane • Gd loading: 3 recipes developed @Heidelberg & LNGS • Gd-CBX • Good stability @20oC • Suitable baseline – End of development • Gd-Acac • Good stability @20oC • Low solubility in PXE  warning • Difficult to purify • Gd-Dmp • Good stability @20oC • High solubility in PXE+dodecane • OK for purification • Synthesis to optimize 3+Gd LY~8000 /MeV L = 5-10 m 6 g/l PPO 20 mg/l BisMSB Gd-Acac Gd-Dmp Gd-Carboxylate R.Svoboda

  45. Long Term Stability: Solved Eur.Phys.J. C27(2003)331-374 Double Chooz Chooz R.Svoboda

  46. Technological Challenge Backgrounds R.Svoboda

  47. Accidental Backgrounds Mainly at Low E This was 1/3 of Chooz background Significanteffort has gone into reducing this: expect ~10 Hz at 1 MeV Correlated Backgrounds Mainly from cosmic muons Best measurements from KamLAND but hard to extrapolate to shallow depth Better to use Chooz reactor off data n + Gd   ~ 8 MeV E >~ 1 MeV n deposits energy n Gd  ~ 8 MeV Two Kinds accidental background (uncorrelated) correlated background +-n cascades R.Svoboda

  48. Li-9 crossing the detector Likely to be seen by the Veto 8He 9Li 11Li β decayed followed by n emission within 200 ms ! μ interaction on 12C R.Svoboda

  49. Chooz Data Period 1&2: 24.1 days RxOFF 174.7 days RxON Period 3: 114.1 days RxOFF 22.1 days RxON 138 days RxOFF197 days RxON R.Svoboda

  50. Importance of Having Reactor Off Data R.Svoboda

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