Christian Buck, MPIK Heidelberg for the Double Chooz Collaboration LAUNCH March 23rd, 2007 The Double Chooz experiment

Outline  Motivation  The Double Chooz Concept and Design  Scintillator development at MPIK  Summary

Why Double Chooz ?  Improved knowledge of mixing matrix  Θ 13 controls 3 flavor effects (e.g. CP violation only for Θ 13 > 0)  Discovery potential: models often close to experimental bound  Complementarity to beam experiments - Degeneracies + parameter correlations - Optimize future experiments  Discrimination power for normal hierarchy in 0νββ depends on Θ 13 Δm sol 2 ~ 8∙10 -5 eV 2, sin 2 (2Θ 12 ) ~ 0.86 Δm atm 2 ~ 2.5∙10 -3 eV 2, sin 2 (2Θ 23 ) ~ 1 ν2ν2 Δm atm 2 Δm sol 2 ν1ν1 ν3ν3 sin 2 Θ 13 sin 2 Θ 23 sin 2 Θ 12 νeνe νμνμ ντντ

 Interest of International Atomic Energy Agency (IAEA) in ν e detection -Monitoring of single reactors -Monitoring of countries  Intensity and shape of spectrum depend on isotopic composition  Pu content!  Use Double Chooz near detector as prototype for reactor monitoring  Thermal power (1% ?) Non-proliferation

Current proposals  December 2002: 1st European meeting, MPIK  April 2003 – February 2005: 4 int. workshops in U.S., Germany, Japan and Brazil  1st Double Chooz Meeting: Nov 2003 Angra Double-Chooz Kaska Daya bay RENO

Double Chooz collaboration  Spokesman: H. de Kerret (APC)  France: CEA/Dapnia Saclay, APC, Subatech (Nantes)  Germany: MPIK Heidelberg, TU München, EKU Tübingen, Universität Hamburg, RWTH Aachen  Italy: LNGS (Gran Sasso)  Russia: RAS, Kurchatov Institute (Moscow)  USA: Alabama, ANL, Chicago, Drexel, Kansas State, LLNL, LSU, Notre Dame, Tennessee  Spain: CIEMAT  Japan: HIT, Kobe, MUE, Niigata, Tohoku, TGU, TIT, TMU  England: University of Oxford

The Double Chooz concept ν ν ν ν ν ν ν ν 1051 m 280 m Site location: France D near D far

The labs Far detector (300 m w.e., 1.05 km)Near detector (75 m w.e., 280 m) Δm 2 atm = 2.8·10 -3 eV 2 (MINOS best fit) Constant flux ratios

Improving Chooz 0.3 %1.5 %Det.eff. < 0.6%2.7 %Σ system. 0.4%2.8%Statistical 0.2 %0.8 %# protons <0.1 %0.7 %Power <0.1 %0.6 %E/fission <0.1 %1.9 %Flux, σ DCChoozerror CHOOZ limit sin 2 (2θ 13 ) < 0.12 – 0.20 R = 1.01  2.8%(stat)  2.7%(syst) Reactor Detector Δm 2 (eV) 2 sin 2 (2Θ)

Sensitivity 2008 Sensitivity 2008 – 2013 (near detector starts 16 months after far) for  m 2 atm = 2.8·10 -3 eV 2

Detector design TARGET: (th = 2,3m) - Acrylic vessel (th = 8mm) - 10,3 m 3 LS (1 g/l Gd) γ-catcher: (th = 0,55m) -Acrylic vessel (th = 12mm) - 22,6 m 3 LS Buffer: (th = 1,05m) -Steel vessel (th = 3 mm) -114 m 3 mineral oil Inner veto: (th = 0,5m) -Steel vessel th = 10 mm) -~80 m 3 LS SHIELDING (th = 17 cm) - Steel 7m

Neutrino signal n e p 511 keV e+e+  ~ 8 MeV Gd Target: Gd-loaded liquid scintillator Events/200 KeV/3 years sin 2 (2  13 )=0.04 sin 2 (2  13 )=0.1 sin 2 (2  13 )=0.2 Energy [MeV] Neutrino rates: - far: ~70/day - near: ~1000/day

Correlated backgrounds n  ~ 8 MeV n deposits energy Gd Fast neutrons Chooz rate: ~1/day Double Chooz simulation:  Far: N b < 0.6/day (90% CL)  Near: N b ~ 3.3/day (90% CL) β-n-cascades (spallation products: 9 Li, 11 Li, 8 He) Expected rate: Far: 1.4/day, Near: 9/day Long-lived

Mockup  Goal: - Find technical solutions - Define interfaces - Material compatiblity - Test filling procedure  Volumes: liter Target liter Gamma Catcher liter Buffer  Match scintillator properties: - Densities (1 % in DC) - Light yield

Filling system  Simultaneous filling  Air driven pumps  Tubing and valves PFA  Filling 2005 MPIK-HD

Mockup results  Gd-concentration unchanged  Optical properties stable

Metal loaded scintillators  Development at MPIK since 2000 (C.Buck, F.X.Hartmann, D.Motta, T.Lasserre, S.Schönert, U.Schwan)  Wide interest in different fields: -Solar neutrino physics (In, Yb,…) -Reactors experiments (Gd) -Geo-neutrinos (Gd) -0νββ-decay ( 150 Nd)

Scintillator development at MPIK Metal-β-diketonates: R1R1 3+ M R2R2 O O O O O O HC - C-C- H C-C- H R1R1 R1R1 R2R2 R2R2 How to dissolve metal in organic scintillator?  Method 1: Organometallic compound Requirements:  solubility  no light quenching  optical transparency  radiopurity  low reactivity (stability!) Method 2: Carboxylate system stabilized by pH (since 2000)

Attenuation length / stability  Stability tests up to 3 years  Tests of concentrates  Temperature tests  Cross check in Saclay  Measured by UV/Vis  10 cm cells  Absorption + Scattering!  No fluors: > 10 m in ROI ROI

Scintillator stability Palo Verde: A.G.Piepke, S.W.Moser, V.M.Novikov NIM A 342 (1999) Chooz: Time variation fit of attenuation length: Parameter v Chooz: (4.2 ± 0.4)∙10 -3 /d * BDK-system: ≤ 7.5∙10 -5 /d * Chooz Coll., Eur. Phys. J. C27, (2003) [v = (1.5 – 2.8)·10 -3 /d)]

Scintillator system Excitation by ionizing particle PMT Metal Secondary wavel. shifter Fluorsolvent

Gd complex  Approach: Gd-β-diketone  Purification by sublimation  Full scale production started! 8· · < 2.4· Conc. [g/g] < 0.03A/det. [Bq] Th 0.005< A/kg [Bq] KU GeMPI at LNGS (M.Laubenstein)

Scintillator solvent PXE/dodecane mixture (20/80 Vol):  Optimized ratio - PXE improves light yield - Dodecane improves material compatibility + number of H  Column purification  High flash point, low toxicity  Solvents used in KamLand (Dodecane), Borexino (PXE in CTF)  Backup Linear alkylbenzene

Fluor choice Primary fluor properties:  Light yield  Emission spectrum  Energy transfer parameters  Transparency  Radiopurity Scintillator emission spectrum

Energy transfer model M  DA * excitation M M M O C H In O O O O O Me. C.Buck, F.X.Hartmann, D.Motta, S.Schönert, Chem.Phys.Lett.435 (2007) 252 – 256 Developed for Indium system

Scintillator Summary  2000 – 2003: Development metal loaded scintillator (In, Yb, Nd, Gd)  2003: First tests Gd-loaded scintillators –Gd(acac) 3 scintillator –pH controlled carboxylate (TMHA) scintillator  2004: Optimization synthesis  2005: Double Chooz mockup  2006: Outsourcing of Gd-BDK production –Successful sublimation at company –First radiopurity measurements

Summer 2006: New division 3 x 24m 3 Iso-containersLarge scale production Gd-material Scintillator building 60 m³ liquids

Scintillator hall Dec 06Jan 07 Feb 07Mar 07

Summary  Double Chooz searches for the neutrino mixing angle θ 13 - Sensitivity: sin 2 (2Θ 13 ) < (90% CL) (Chooz bound sin 2 (2Θ 13 ) < 0.2) - Start data taking: 2008  Main hardware contribution of MPIK: -Development + production target Gd-scintillator (10.3 m³) -Tuning + production of γ-catcher scintillator (22 m³) -Design and construction scintillator mixing system  Status -Major components ordered -Construction of scintillator hall