Christian Buck, MPIK Heidelberg LAUNCH 09 November, 11th 2009 The Double Chooz reactor neutrino experiment

Neutrino oscillations Δm sol 2 ~ 7.6∙10 -5 eV 2, sin 2 (2Θ 12 ) ~ 0.85 Δm atm 2 ~ 2.4∙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

Why Double Chooz ?  Improved knowledge of mixing matrix  Key experiment to unveil leptonic CP violation  Discovery potential: hint given by global analysis Fogli et al., arXiv: (2009)  Complementarity to beam experiments - Degeneracies + parameter correlations - Optimize future accelerator experiments  Discrimination power of 0νββ  Safeguard applications,…

Reactor neutrino experiments 1956: First observation (Nobel Prize 1995) 1990s: Chooz, Palo Verde (sin 2 2Θ 13 < 0.2) 2002: KamLand Δm 12, Θ 12 Reactor neutrinos:  Pure ν e - beam  Intense flux (~2% precision)  Detection: inverse β-decay  Energy: few MeV

Double Chooz collaboration  Spokesman: H. de Kerret (APC)  France: CEA Saclay, APC Paris, Subatech Nantes, IPHC Strasbourg  Germany: MPIK Heidelberg, TU München, EKU Tübingen, Universität Hamburg, RWTH Aachen  USA: Univ. of Alabama, Argonne Nat. Lab., Chicago, Drexel, Kansas State, LLNL, Notre Dame, Tennessee, Columbia Univ., Davis, MIT, Sandia  Spain: CIEMAT Madrid  Japan: Tohoku University, Kobe University, Tokyo Inst. of Tech., Niigata University, Tokyo Metropolitan University, Hiroshima Inst. of Tech.  England: University of Sussex  Russia: RAS Moskau, Kurchatov Institute  Brasil: CBPF Rio de Janeiro, UNICAMP

The Double Chooz principle

Survival probability G. Mention (APC) D near D far Survival probability assuming sin 2 (2Θ 13 ) = 0.2 for different Δm 13

Current proposals Angra Double-Chooz Kaska Daya bay RENO

Neutrino signal n e p 511 keV e+e+  ~ 8 MeV Gd Target: Gadolinium loaded liquid scintillator Neutrino rates: - far: ~50/day - near: ~300/day 235 U β β 236 U n  pure e source  E ν ~ MeV  E min ~ 1.8 MeV  > /(s∙GW) Chooz: ~ 7.4 GW th prompt delayed (30 µs)

Background Accidentals n  ~ 8 MeV +  E  ≥ 1 MeV Gd n  ~ 8 MeV Gd fast neutrons β-n-cascades: 9 Li, 8 He Chooz data: far detector: ca. 1.4/day Long lived!

Detector Design TARGET (2.3m) - Acrylic vessel (8mm) - 10,3 m 3 LS (1 g/l Gd) γ-catcher (0.55m) - Acrylic vessel (12mm) - 22,6 m 3 LS Buffer (1.05m) -Steel (3 mm) m 3 oil Inner Veto (0.5m) -Steel (10 mm) - 80 m 3 LS 7m

Calibration systems Target GC Buffer Articulated arm z-axis system (glove box) Guide tube / wire sources LED system / multi-wavelength Buffer tube

Comparison with Chooz FehlerChoozDC Statistical2.8%0.4% Flux, σ1.9 %<0.1 % E/fission0.6 %<0.1 % power0.7 %<0.1 % # protons0.8 %0.2 % Det.eff.1.5 %0.5 % Σ System.2.7 %~ 0.6% Best limit: CHOOZ sin 2 (2θ 13 ) < 0.15 (90% CL) for  m 2 atm = 2.5·10 -3 eV 2 R = 1.01  2.8%(stat)  2.7%(syst) Reactor Detector

Sensitivity 2010 Sensitivity 2010 – 2015 (near detector starts < 2 y after far) for  m 2 atm = 2.8·10 -3 eV 2 Far detector filling early 2010!

Far detector installation Lab cleaning Installation Veto and Veto-PMTsInstallation Buffertank

PMT installation

Acrylic vessel installation Arrival Gamma Catcher on-siteAcrylic vessels in lab Gamma Catcher installationGamma Catcher transport

Status October ‘09

Status near detector Tunnel (155 m), 12%  Site engineering study completed  excavate 2010  r = 415 m (115 m w.e.)  Myons (Veto): 250 Hz reactors near detector Laboratory Open ramp (85 m), 14% Liquid storage Data taking: 2011

Scintillator development (MPIK) Requirements:  Gd-solubility > 1 g/l  Stability (5 years)  Transparency  Material compatibility  Radiopurity  Target – Gamma catcher matching (optics + density)  Large scale (multi tons) Light yield PXE conc, PPO conc.

Scintillator properties Target Gamma Catcher candidates Event localization by pulse shape analysis Transparency in ROI stable in 10 m range! Time [ns] Events

 All components (40 tons) delivered to MPIK  Purifications finalized, prepare for mixing  Scintillator production starts Large scale production

PMT activities at MPIK  Testing / Calibration  Assembly / Installation  Implementation of data in Double Chooz software  Current upgrade: full detector segment

PMT calibration Calibration program:  HV scans  Single photon electron (P/V)  Transit time  Dark rate  Quantum efficiency

Summary  Goal of Double Chooz reactor neutrino experiment: Determination of mixing angle Θ 13 (sin 2 (2θ 13 ) ~ 0.03)  2-detector concept to reduce systematical error  Detection via inverse β-decay in Gadolinium loaded liquid scintillator  Schedule: –Data taking far detector: Spring 2010 –Near detector: end of 2011  MPIK: scintillators, PMTs, Analysis

Θ 13 and 0νββ Normal hierarchy: discrimination power of 0 ν ββ-exp. depends on sin 2 (2 Θ 13 ) ! M.Lindner, A.Merle, W.Rodejohann, Phys.Rev.D73: (2006)

Positron spectrum Far/Near ratio sin 2 (2  13 )=0.12 e + spectrum Far Detetector Stat. Errors

Sensitivity (rate vs shape)

Robustness