1. The Quest for θ 13 with the Double Chooz Detector Jelena Maričić Drexel University On behalf of On behalf of the Double Chooz Collaboration

2. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 2 Outline Physics motivation for the Double Chooz experiment –Repetitio est mater studiorum Challenges of the high precision reactor neutrino experiment Detector overview Future prospects

3. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 3 Neutrino oscillations atmospheric  solar  leptonic CP phase  CHOOZ  13 < 13  e, ,  ( e, ,  ) T = U ( 1, 2, 3 ) T U =matrice PMSN : 3 angles,1cp violation phase (+2 mass differences) Leptonic CP violation phase  completely unknown Θ 13 small  directly affects prospects of measuring leptonic CP violation phase Θ 13 small  directly affects prospects of measuring leptonic CP violation phase θ 23 ~ 45  θ 12 ~ 32  The future quest for  13 Accelerators Reactors *CP violation is responsible for matter- antimatter asymmetry Leptons = Leptons = e, , , e, , 

4. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 4  13 & Accelerator Experiments Appearance probability :  dependences in sin(2  23 ), sin(  23 ), sign(  m 2 31 ),  -CP phase in [0,2  ]  13 & Reactor Experiments ~ a few MeV  only disappearance experiments  sin 2 (2  13 ) measurement independent of  -CP 1-P( e  e ) = sin 2 (2  13 )sin 2 (  m 2 31 L/4E) + O(  m 2 21 /  m 2 31 )  weak dependence in  m 2 21 a few MeV e + short baselines  negligible matter effects (O[10 -4 ] )  sin 2 (2  13 ) measurement independent of sign(  m 2 13 )

5. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 5 How well can We Measure CP Violation? Hopeless without beam upgrade Even with beam upgrade chance <15% If sin 2 2θ 13 < 0.025 NOvA and T2K will not start before 2011. It would be great to know ASAP if the value of θ 13 is large or small Courtesy of R. Svoboda

6. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 6 Best current constraint: CHOOZ World best constraint! @  m 2 atm = 2 10 -3 eV 2 sin 2 (2θ 13 ) < 0.2 (90% C.L) e  x M. Apollonio et. al., Eur.Phys.J. C27 (2003) 331-374 e  e ( disappearance experiment) P th = 8.4 GW th, L = 1.050 km, M = 5 t overburden: 300 mwe R = 1.01  2.8%(stat)  2.7%(syst)

7. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 7 Challenges of the High Precision Reactor Neutrino Experiment

8. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 8 Reactor Neutrino Detection Signature Reactors are tremendous sources of neutrinos: P = 8GW  N ~10 21 s -1 Neutrino detection: Distinctive two-step signature: -prompt event Photons from e + annihilation E e = E  + 0.8 MeV + O(E e /m n ) -delayed event Photons from n capture on dedicated nuclei (Gd)  t ~ 30  s E ~ 8 MeV Gd +  Tiny

9. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 9 Expected Backgrounds in Reactor Neutrino Experiments Accidental bkg: e + -like signal: radioactivity from materials, PMTs, surrounding rock Rate=R e n signal: n from cosmic  spallation, thermalized in detector and captured on Gd (R n )  Accidental coincidence Rate = R e x R n x Δt Correlated bkg: fast n (by cosmic  ) recoil on p (low energy) and captured on Gd long-lived ( 9 Li, 8 He)  -decaying isotopes induced by  Bkg reduction and knowledge is critical for oscillation measurement !

10. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 10 How Can We Improve Limit on θ 13 Based on Experience with CHOOZ ? CHOOZ : R osc = 1.01 ± 2.8% (stat) ± 2.7% (syst) Statistics – –More powerful reactor (multi-core) – –Larger detection volume – –Longer exposure Experimental error: flux and cross-section uncertainty – –Multi-detector – –Identical detectors to reduce inter-detector systematics (goal: towards σ relative ~0,6%) Background – –Improve detector design larger S/B – –Increase overburden – –Improve bkg knowledge by direct measurement – –subtraction error<1%  Luminosity increase L =  t x P(GW) x Np Far: 60 000/3 y Near: ~3 10 6 /3 y 2700Event rate 3-5 yearsFew monthsData taking period 0,5%2,7%Statistical error 6,82 10 28 H/m 3 6,77 10 28 H/m 3 Target composition 10,2 m 3 5,55 m 3 Target volume Double-ChoozCHOOZ

11. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 11  13 at Reactors: The Double Chooz a New Experimental Concept  13 2 P( e  e ) ~ 1 - sin 2 2  13 sin 2 (  m 2 13 L/4E)+… Reactor e e ? Far Detector 280 m 1,050 m Near Detector

12. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 12  13 at Reactors sin 2 (2  13 )=0.04 sin 2 (2  13 )=0.1 sin 2 (2  13 )=0.2  m 2 atm = 2.0 10 -3 eV 2 Near Detector: ~ 3 10 6 events/3y -Reactor efficiency: 80% -Detector efficiency: 80% -Dead time: 50% Far Detector: ~ 60 000 events/3y -Reactor efficiency: 80% -Detector efficiency: 80% Events/200 KeV/3 years E (MeV) Two independent sets of information: Normalisation + Spectrum distortion

13. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 13 Detector Overview

14. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 14 The Chooz Site 80 m.w.e.300 m.w.e. Chooz-B reactors ~1000 ev/day ~70 ev/day

15. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 15 Reactor-Induced Systematics 997.9m 1114.6m 260.3m 290.7m Distance ratio exactly cancels reactor thermal power uncertainty. Uncertainty due to solid angle is 0.06%

16. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 16 The detector design 7 m Shielding : steel 17 cm: >7  Muon Inner-VETO : scintillating oil Non-scintillating buffer : same liquid (+ quencher?) Isolate PMTs from target area  -catcher : 80% dodecane + 20% PXE Extra-volume for -interaction -target : 80% dodecane + 20% PXE + 0.1% Gd Volume for -interaction n e p Gd  ~ 8 MeV 511 keV e+e+ Muon Outer-VETO : Acrylic vessels  «hardware» definition of fiducial volume PMT support structure: steel tank, optical insulation target/veto  Improved background reduction 7m

17. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 17 The detectors Muons VETO (shield) Inner radius = 3,471m Thickness = 200mm Acrylic Gamma catcher vessel (Inner radius = 1,696m Inner H = 3,55 m t = 12mm) LS + 0,1%Gd LS Acrylic Target vessel (Inner radius =1,15m H = 2,474m t = 8mm) Stainless steel Buffer (Inner radius = 2,758m Inner H = 5,674m t = 3mm)

18. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 18 Technological Challenges

19. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 19 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. Double Chooz goal is 0.6% relative uncertainty.

20. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 20 How will We 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 4  system) We will control detector temperature at Near and Far Detector with active heating. We will remix scintillator when starting Near Detector, or else throw away 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  metal shields.

21. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 21 …And We have developed 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%) Swap calibration systems, which can be done easily, cheaply, and at the same time

22. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 22 Scintillator Stability Studies Long term stability is essential for near-far detector comparison Results on the different formulation now available on 2 years’ tests. Validation through optical monitoring of the liquids. 3+ Gd Solvant: 20% PXE – 80% Dodecane Gd loading: being developed @MPIK & LNGS 0.1% Gd loading Two formulations under study: Gd-CBX Based on Carboxilic acids (+stabilizers) Gd-Acac & Gd-Dmp Beta Dikitonate   Long term Stability LY ~7000 ph/MeV: 6 g/l ppo + 50 mg/l Bis-MSB Attenuation length: a few meters at 420 nm LY~8000  /MeV L = 5-10 m

23. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 23 Last stage for the validation of the technical choices for vessels construction, material compatibility, filling, and the integration of the detector at the Chooz site - - Inner Target: 120 l : 20%PXE+80%dodecane+0.1%Gd - - Gamma Catcher: 220 l : 20%PXE+80%dodecane Total of 2000 l of oil Filling 13/12/2005 Stable in the detector All teflon filling system A 1/5 prototype

24. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 24 Muon simulation Knowledge of  fluxes at underground experiments is essential for a precise determination of the induced backgrounds: spallation n’s, radioactive nuclei, bremsstrahlung  ’s… A measurement of  distribution was performed at Chooz in 1995. They were correctly parametrized, but no detailed information on the energy spectrum was available. Measured angular distributions are well reproduced Energyspectrum Spallation fast neutron μ capture Recoil p n capture on Gd Gd Recoil p n from  capture μ μ Detailed simulation with MUSIC + rock composition + hill profile: Phys.Rev.D74: 053007,2006 [hep-ph/0604078]

25. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 25 Relative Normalization: Analysis @Chooz: 1.5% syst. err. - 7 analysis cuts - Efficiency ~70% Goal Double-Chooz: ~0.3% syst. err. - 2 to 3 analysis cuts Selection cuts - neutron energy (- distance e+ - n ) [level of accidentals] -  t (e+ - n) e+e+ n tt n e p Gd e+e+

26. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 26 Data Acquisition System Level 1 trigger (analog sum above 0.5 MeV) FIFO Level 2 trigger (2 coincident Level 1 triggers) Storage Event builder ( -like   -tagged) Flash-ADC CAEN N(V)1726 developed by APC-Paris + CAEN 4 channels Wave-form sampling @ 500MHz 8-bit resolution (few PEs/ch for  evts) Continuous digitising with zero deadtime (if DAQ sustains trigger rate) 2  s waveform data recording Zero dead-time DAQ ~ 400 (target) + 100 (veto) PMTs NIM version available, under test @APC Several components of VME version ready

27. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 27 Prospects with Double Chooz

28. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 28 Double Chooz Timeline 2003200420052006200720082009… …2011 SiteProp. design+test simulation Data taking and analysis Construction Data Taking mid 2008 Far detector completion > 1 year sin 2 2  13 > ~0.07 with far detector alone 2009 Near detector completion > 1 year sin 2 2  13 > 0.04 with 2 detectors > 3 yearsin 2 2  13 > 0.02-0.03 with 2 detectors 90% C.L. Double Chooz will improve the limit on the limit on sin 2 2  13 significantly and soon!

29. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 29 The Double Chooz Collaboration Spokesperson: H. de Kerret (APC) Over 100 members in the collaboration group of ~120 scientists from 8 countries France, U.S., Germany, Spain, Russia, Italy, Brazil, U.K., Japan Very Experienced: Chooz, Bugey, KamLAND, Super- Kamiokande, SNO,Borexino

30. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 30 Conclusion and Summary Double Chooz is a significant technological challenge. There has been a huge amount of work done to control systematics in order to minimize technological and cost risk. Backgrounds are under control. It is a huge advantage to have data from a previous neutrino experiment at the same site. The collaboration is extremely experienced, with many members having done several previous reactor experiments. The schedule is conservative and realistic. Double Chooz will achieve an unprecedented high precision measurement for a reactor neutrino experiment. Great gain in knowledge that will in prospect help get tighter constraints on geo-neutrino measurements with future detectors.

31. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 31

32. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 32 Complementarity with Superbeams 3  discovery potential 3  sensitivity (no signal) For a fair comparison of Reactor & Beam programs, both information should always be quoted together!

33. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 33 ChoozDouble-Chooz Reactor- induced flux and  1.9 %<0.1 % Two ‘’identical’’ detectors, Low bkg Reactor power0.7 %<0.1 % Energy per fission 0.6 %<0.1 % Detector - induced Solid angle0.3 %<0.1 % Distance measured @ 10 cm + monitor core barycenter Volume0.3 %0.2 %Same weight sensor for both det. Density0.3 %<0.1 %Accurate T control (near/far) H/C ratio & Gd concentration 1.2 %<0.1 % Same scintillator batch + Stability Spatial effects1.0 %<0.1 %‘’identical’’ Target geometry & LS Live timefew %0.25 %Measured with several methods AnalysisFrom 7 to 3 cuts1.5 %0.2 - 0.3 %(see next slide) Total2.7 %< 0.6 % Systematics

34. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 34 Near detector location Uncorrelated fluctuations included Relative Error : 0.6% Spectral shape uncertainty 2%  m 2 known at 20% Power flucutation of each core: 3% On the median Available and suitable area 3 years data taking ~10% ~250 m

35. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 35   10‘‘ Ultra low background tubes   365 PMTs   13 % coverage   Energy resolution goal: 7 % at 1 MeV   Current work: PMT selection (radiopurity) ETL 9354KB ? Hamamatsu R5912 ? Photonis: XP1806 ? Angular sensitivity, Concentrators? Tilting tube options Cabling & Tightness B fields shielding Phototubes baseline

36. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 36 Relative Normalization: Analysis @Chooz: 1.5% syst. err. - 7 analysis cuts - Efficiency ~70% Goal Double-Chooz: ~0.3% syst. err. - 2 to 3 analysis cuts Selection cuts - neutron energy (- distance e+ - n ) [level of accidentals] -  t (e+ - n) e+e+ n tt n e p Gd e+e+

37. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 37 How well can they resolve the mass ordering problem? Phase 1 has no chance of even 2  if sin 2 2   < 0.025 Billion $ upgrade

38. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 38 Fit Using Extended Spectrum Fit Range 9-Li flat Fitted flat backround rate <8 MeV is 254/114 days =2.23(0.14) d -1 Consistent with published paper

39. DOANOW, Honolulu 03/24/2007J. Maricic-Double Chooz 39 Role of θ 13 in Neutrino Oscillations e, ,  ( e, ,  ) T = U ( 1, 2, 3 ) T U =matrice PMNS : 3 angles,1CP violation phase (+2 mass differences) Only the upper limit on the value of angle θ 13 has been set! Value of θ 13 directly influences prospects of measuring CP violation phase in the weak sector! World best constraint: CHOOZ experiment! ( e  e disappearance exp) @  m 2 atm = 2 10 -3 eV 2 sin 2 (2θ 13 ) < 0.2 (90% C.L) Chooz experiment R = 1.01  2.8%(stat)  2.7%(syst) e  x M. Apollonio et. al., Eur.Phys.J. C27 (2003) 331-374 The future quest for θ 13 Accelerators Reactors s 13  sin θ 13