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. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 2 Outline Physics motivation for the Double Chooz experiment Challenges of the high precision reactor neutrino experiment Detector overview Future prospects

3. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 3 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

4. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 4  13 & Beam 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. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 5 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 + 

6. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 6 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 !

7. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 7 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

8. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 8  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

9. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 9  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

10. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 10 Detector Overview

11. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 11 The Chooz Site 80 m.w.e.300 m.w.e. Chooz-B reactors ~1000 ev/day ~70 ev/day

12. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 12 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

13. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 13 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)

14. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 14 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

15. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 15 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

16. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 16 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

17. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 17 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]

18. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 18 Prospects with Double Chooz

19. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 19 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!

20. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 20 The Double Chooz Collaboration France: APC - IN2P3 DAPNIA CEA/Saclay Subatech - IN2P3 Germany: Eberhard-Karls Universität Tübingen Max Planck Institut für Kernphysik HeidelbergMax Planck Institut für Kernphysik Heidelberg Technischen Universität München Physikalisches Institut RWTH Aachen Universität Hamburg Japan: Hiroshima Institute of Technology Kobe University Miyagi University of Education Niigata University Tohoku University Tohoku Gakuin University Tokyo Institute of Technology Tokyo Metropolitan University Russia: Institute for Nuclear Research RAS Institue of Physical Chemistry RAS RRC Kurchatov Institute Spain: CIEMAT UK: University of Oxford University of Sussex USA: Argonne National Laboratory University of Chicago Columbia University Drexel University Illinois Institute of Technology Kansas State University Lawrence Livermore National Laboratory Louisiana State University Sandia National Laboratories University of Alabama University of California at Davis University of Notre Dame University of Tennessee Members contributing in Italy from: INFN, Laboratori Nazionale del Gran Sasso Spokesperson: H. de Kerret (APC) Over 100 members in the collaboration

21. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 21

22. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 22 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!

23. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 23 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

24. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 24 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

25. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 25   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

26. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 26 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+

27. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 27 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

28. C2CR07, Tahoe 03/01/2007J. Maricic-Double Chooz 28 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