Jelena Marii Drexel University On behalf of the Double Chooz CollaborationThe Quest for 13 with the Double Chooz Detector

OutlinePhysics motivation for the Double Chooz experimentChallenges of the high precision reactor neutrino experimentDetector overviewFuture prospects

Role of 13 in Neutrino Oscillations(ne,nm,nt)T = U (n1,n2,n3)T U=matrice PMNS : 3 angles,1CP violation phase(+2 mass differences)Only the upper limit on the value of angle 13 has been set!Value of 13 directly influences prospects of measuring CP violation phase in the weak sector! World best constraint: CHOOZ experiment!(e e disappearance exp)@m2atm = 2 10-3 eV2sin2(213) < 0.2 (90% C.L)Chooz experimentR = 1.01 2.8%(stat)2.7%(syst)e xM. Apollonio et. al., Eur.Phys.J. C27 (2003) 331-374 The future quest for 13AcceleratorsReactorss13 sin 13

13 & Beam ExperimentsAppearance probability : dependences in sin(223), sin(23), sign(m231), -CP phase in [0,2]

Reactor Neutrino Detection SignatureReactors are tremendous sources of neutrinos:

P = 8GW N~1021s-1 Neutrino detection:Distinctive two-step signature: -prompt event Photons from e+ annihilation Ee = E+ 0.8 MeV + O(Ee/mn) -delayed event Photons from n capture on dedicated nuclei (Gd) t ~ 30 s E ~ 8 MeVGd+

Expected Backgrounds in Reactor Neutrino ExperimentsAccidental bkg:e+-like signal: radioactivity from materials, PMTs, surrounding rock Rate=Ren signal: n from cosmic spallation, thermalized in detector and captured on Gd (Rn) Accidental coincidenceRate = Re x Rn x tCorrelated bkg:fast n (by cosmic ) recoil on p (low energy) and captured on Gdlong-lived (9Li, 8He) -decaying isotopes induced by Bkg reduction and knowledge is critical for oscillation measurement !

How Can We Improve Limit on 13 Based on Experience with CHOOZ ?CHOOZ : Rosc = 1.01 2.8% (stat) 2.7% (syst)StatisticsMore powerful reactor (multi-core)Larger detection volumeLonger exposure

Experimental error: flux and cross-section uncertaintyMulti-detectorIdentical detectors to reduce inter-detector systematics (goal: towards relative~0,6%)

BackgroundImprove detector design larger S/BIncrease overburdenImprove bkg knowledge by direct measurementsubtraction error

13 at Reactors: The Double Chooz a New Experimental Concept132P(ee) ~ 1 - sin2 213 sin2(m213L/4E)+Reactornene?Far Detector280 m1,050 mNear Detector

13 at Reactors sin2(213)=0.04 sin2(213)=0.1 sin2(213)=0.2m2atm = 2.0 10-3 eV2Near Detector: ~ 3 106 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 yearsE (MeV)E (MeV)Two independent sets of information:Normalisation + Spectrum distortion

Detector Overview

The Chooz Site80 m.w.e.300 m.w.e.Chooz-B reactors~1000 ev/day~70 ev/day

The detector design7 mShielding: steel 17 cm: >7Muon Inner-VETO: scintillating oilNon-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 -interactionMuon Outer-VETO: Acrylic vessels hardware definition of fiducial volumePMT support structure: steel tank, optical insulation target/veto Improved background reduction7m

The detectorsMuons VETO(shield)Inner radius = 3,471mThickness = 200mmAcrylic Gamma catcher vessel(Inner radius = 1,696mInner H = 3,55 mt = 12mm)LS + 0,1%GdLSAcrylic Target vessel(Inner radius =1,15mH = 2,474mt = 8mm)Stainless steel Buffer(Inner radius = 2,758mInner H = 5,674mt = 3mm)

Scintillator Stability StudiesLong term stability is essential for near-far detector comparisonResults on the different formulation now available on 2 years tests. Validation through optical monitoring of the liquids.3+GdSolvant: 20% PXE 80% DodecaneGd 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

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 13/12/2005Stable in the detectorAll teflon filling systemA 1/5 prototype

Data Acquisition SystemFlash-ADC CAEN N(V)1726developed by APC-Paris + CAEN4 channelsWave-form sampling @ 500MHz 8-bit resolution (few PEs/ch for evts)Continuous digitising with zero deadtime (if DAQ sustains trigger rate) 2s waveform data recordingZerodead-time DAQ~ 400 (target) + 100 (veto) PMTsNIM version available, under test @APCSeveral components of VME version ready

Muon simulationKnowledge of fluxes at underground experiments is essential for a precise determination of the induced backgrounds: spallation ns, radioactive nuclei, bremsstrahlung sA 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 Energy spectrumDetailed simulation with MUSIC + rock composition + hill profile:Phys.Rev.D74:053007,2006 [hep-ph/0604078]

Prospects with Double Chooz

Double Chooz Timeline2003200420052006200720082009 2011Site

Prop. design+testsimulationData taking and analysisConstruction

Data Takingmid 2008 Far detector completion> 1 year sin2213 > ~0.07 with far detector alone2009 Near detector completion> 1 year sin2213 > 0.04 with 2 detectors> 3 yearsin2213 > 0.02-0.03 with 2 detectors

90% C.L.Double Chooz will improve the limit on sin2213 significantly and soon!

The Double Chooz CollaborationFrance: APC - IN2P3 DAPNIA CEA/Saclay Subatech - IN2P3 Germany: Eberhard-Karls Universitt Tbingen Max Planck Institut fr Kernphysik Heidelberg Technischen Universitt Mnchen Physikalisches Institut RWTH Aachen Universitt 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

Complementarity with Superbeams 3 discovery potential3 sensitivity (no signal)For a fair comparison of Reactor & Beam programs, both information should always be quoted together!

Systematics

ChoozDouble-ChoozReactor-induced flux and 1.9 %

Near detector location Uncorrelated fluctuations included Relative Error : 0.6% Spectral shape uncertainty 2% m2 known at 20% Power flucutation of each core: 3%Available and suitable area3 years data taking~10%~250 m

10 Ultra low background tubes 365 PMTs 13 % coverageEnergy resolution goal: 7 % at 1 MeVCurrent work:PMT selection (radiopurity) ETL 9354KB ?Hamamatsu R5912 ?Photonis: XP1806 ?

Angular sensitivity, Concentrators?

Tilting tube options

Cabling & TightnessB fields shieldingPhototubes baseline

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+n t

How well can they resolve the mass ordering problem?Phase 1has nochance of even 2sif sin22q13< 0.025 Billion $ upgrade

Fit Using Extended SpectrumFit Range9-LiflatFitted flat backround rate