Double-Chooz A search for  13 Guillaume MENTION (PCC-Collège de France/APC) On behalf of the Double-Chooz collaboration NOW 2004 Conca Specchiulla, Italy September 14 th 2004

G. Mention (PCC/APC) -NOW04- In this presentation 1.Current  13 physical context 2.Chooz site and detector 3.Improving Chooz 4.Backgrounds 5.Detector design 6.Sensitivity and discovery potential 7.Safeguard applications

G. Mention (PCC/APC) -NOW04- Best current constraint: Chooz World best constraint  m 2 atm = eV 2 sin 2 (2θ 13 ) < 0.2 (90% C.L) e  x M. Apollonio et. al., Eur.Phys.J. C27 (2003) e  e (disappearance experiment) P th = 8.4 GW th, L = km, M = 5 t overburden: 300 mwe R = 1.01  2.8%(stat)  2.7%(syst)

G. Mention (PCC/APC) -NOW oscillations Near detector Far detector

G. Mention (PCC/APC) -NOW04- The Double-Chooz concept 8.4 GW th Chooz power station Near detector Far detector e e, ,  anti- e flux (uranium 235, 238 & plutonium 239, 241) Reaction: e + p  e + + n, ~ 4 MeV, E threshold =1.8 MeV Disappearance experiment: search for a departure from the 1/D 2 behavior and shape distortion D 1 = m D 2 = 1,050 m  Improve the detector concept  and backgrounds rejection improve Chooz sensitivity  0.03

G. Mention (PCC/APC) -NOW04- Letter of Intent (hep-ex/ ) AND Drexel, Argonne and Universities of Alabama, Louisiana and Tennessee

G. Mention (PCC/APC) -NOW04- Chooz site & Detector Overview

G. Mention (PCC/APC) -NOW04- Near site: D~ m, overburden mwe Far site: D~1.1 km, overburden 300 mwe 2Cores EDFOperator FramatomeConstructor 66, 57(%, in 2000) 1996/1997Couplage 8.4 GW th Power PWRType Chooz-Far Chooz-Near Double-Chooz, Ardennes, France

G. Mention (PCC/APC) -NOW04- Two detectors

G. Mention (PCC/APC) -NOW04- Far detector laboratory

G. Mention (PCC/APC) -NOW04- Near laboratory Distance Reactor-detectorRequired overburden (m.w.e) , ~10m 60 m.w.e. overburden 12 m compacted earth 3 meter high density material 5m 15m

G. Mention (PCC/APC) -NOW04- Detectors design 7 m Shielding: 0,15 m steel 7 m Muon VETO: scintillating oil (r+0.6 m – V = 110 m 3 ) Non-scintillating buffer: same liquid (+ quencher?) (r+0.95m,, V = 100 m 3 )  -catcher: 80% dodecane + 20% PXE (acrylic, r+0,6m – V = 28,1 m 3 ) PMTs supporting structure target: 80% dodecane + 20% PXE + 0.1% Gd (acrylic, r = 1,2 m, h = 2,8 m, 12,7 m 3 ) n e p Gd  ~ 8 MeV 511 keV e+e+

G. Mention (PCC/APC) -NOW04- How to improve Chooz: statistics & systematics

G. Mention (PCC/APC) -NOW04- Improving Chooz – Statistical error – Luminosity increase L =  t x P(GW) x V target Chooz : R = 1.01  2.8% (stat)  2.7% (syst) ChoozDouble-Chooz Target volume5.55 m 3 12,67 m 3 Target composition H/m H/m 3 Data taking periodFew months3-5 years Number of events2700 Chooz-far : /3 y Chooz-near: > /3 y Statistical error2.7%0.4%

G. Mention (PCC/APC) -NOW04- Decreasing systematical error 1.Improve the detector concept 2.Two identical detectors  towards σ relative ~ 0.6% 3.Backgrounds – improve S/N>100  error < 1% Improving Chooz – Systematical error : σ sys = 2.7%

G. Mention (PCC/APC) -NOW04- Reactor induced systematics systematicsError typeChooz 2 identical detector Low background Reactor Flux, cross section1.9%O(0.1%) Thermal power0.7%O(0.1%) E/Fission0.6%O(0.1%)  2.1% O(0.1%) 2 detectors  cancellation of the reactor physical uncertainties

G. Mention (PCC/APC) -NOW04- Detector induced systematics systematicsError typeChooz 2 identical detector Low backgrounds Detector Scintillator density0.3%O(0.1%) % H1.2%O(0.1%) Target volume0.3%0.2% Boundary effects1.0%O(0.1%) Live timen.g.0.25% M. ApollonioM. Apollonio et. al., Eur.Phys.J. C27 (2003) A single scintillator batch will be prepared to fill both detectors with the same apparatus

G. Mention (PCC/APC) -NOW04- Main works on systematic errors Solid angle - Reactor cores to near detector distance to be cm - Monitoring of the source barycenter … Target volume : 0.3% [simple measurement] - Goal ~ 0.2% [same apparatus for both detectors] – feasible but not trivial… Live time to be measured accurately by several methods KamLAND : dead-time  10% and σ syst = 0.6% Double-Chooz: dead-time(near)  25% and goal: σ syst ~ 0.25%

G. Mention (PCC/APC) -NOW04- Relative Normalization: 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+

G. Mention (PCC/APC) -NOW04- Systematics uncertainties

G. Mention (PCC/APC) -NOW04- Backgrounds

G. Mention (PCC/APC) -NOW04- Uncorrelated and correlated backgrounds n e p Gd  ~ 8 MeV 511 keV e+e+ neutrino identification (signal) n Gd  ~ 8 MeV n deposits energy correlated background accidental background (uncorrelated) prompt signal + n capture on Gd n Gd  ~ 8 MeV +  E  >~ 1 MeV +  -n cascades

G. Mention (PCC/APC) -NOW04- - Chooz: N/S ~ 4% - Double-Chooz-Far (300 mwe): 12.7 m 3  Signal x Uncorrelated ( ,  + n capt. on Gd): N/S(Chooz) ~ 4% : Double-Chooz: Sx3 & N/3  can be measured and subtracted - Correlated events (neutrons): Chooz : ~<1 recoil proton per day Double-Chooz: liquid active buffer +30 cm  ~0.3 events per day  N/S<1% - Double-Chooz-near (50 mwe): Signal x S FAR - Key advantage: D near ~ m  Signal x ! - Uncorrelated: Chooz-Far backgrounds x 50  can be measured and subtracted - Correlated events: Chooz-Far x <30  N/S < 1% (but not a comprehensive list of backgrounds …) Backgrounds Estimates

G. Mention (PCC/APC) -NOW04- Neutron Induced Background Cosmic muons create fast neutrons through spallation and muon capture in the rock surrounding the detector Fast neutron slows down by scattering into the scintillator; it could deposit between 1-8 MeV and be later captured on Gd ! Full simulation – Geant + Fluka Old Chooz simulation: 300 m.w.e. 31hours – MC is reliable ! Simulated: N b <1.6 evts/day (90% C.L.) Measured in-situ: N b =1.1 evts/day Double-Chooz simulation:  tracked – neutrons tracked 1 neutron created a muon event Far detector: N b <0.5 evt/day (90% C.L.) Near detector: N b <3.2 evts/day (90%C.L.)  n Gd  ~ 8 MeV

G. Mention (PCC/APC) -NOW04- Overview of Scintillator development & Acrylic vessel design

G. Mention (PCC/APC) -NOW04- Gd-Acac 3+ Gd Goal: 0.1% Gd loaded scintillator (follow up of LENS R&D)  Light yield ~8000  /MeV + attenuation length > 5m  STABLE & Compatible with acrylic Gd doped scintillator development 3+ Gd ( R-COOH) x R-COO- -OOC-R Carboxylate Ongoing: 1/ Long term stability  20042/ scintillator-acrylic compatibility  ~80 days Ageing o [x2-4 each 10 0 ]  Material compatibility test + acrylic design

G. Mention (PCC/APC) -NOW04- DAPNIA target: 2.8 m  -catcher: 4.0 m  -catcher: 1.8 m target: 1.2 m Acrylic vessels (preliminary) single acrylic piece integration ( -target +  -catcher set)

G. Mention (PCC/APC) -NOW04- Sensitivity & Discovery Potential

G. Mention (PCC/APC) -NOW04- Spectrum 1σ statistical errors only rate info: no-osc 2.66σ shape info: flat shape 5.98σ

G. Mention (PCC/APC) -NOW04- Global normalization: 2% Detector NDetector F σ abs =2% Relative normalization: 0.6% Detector NDetector F σ shape =2% Spectrum shape uncertainty: 2% Detector NDetector F σ bkg =1% Backgrounds subtraction: 1% Systematical errors influence on spectra

G. Mention (PCC/APC) -NOW04- Potential limit if sin 2 (2  13 )=0 Efficiencies included 1% of background in Near & Far detectors Syst. uncert.: σ abs = 2.0% σ rel = 0.6% σ scl = 0.5% σ shp = 2.0% σ Δm 2 = 20%  m 2 = eV 2 3 years (efficiencies included) sin 2 (2  13 )<0.024

G. Mention (PCC/APC) -NOW04- Discovery potential 1 d.o.f.

G. Mention (PCC/APC) -NOW04- Complementarity of Double-Chooz with T2K (3σ discovery potential) sin 2 2θ 13 = 0.08 Double-Chooz 1 year 3 years 7 years J-Parc / 1 year 5 years  m 2 = eV 2 Lindner et al.

G. Mention (PCC/APC) -NOW04- Double-Chooz & IAEA IAEA: International Agency for Atomic Energy Missions: Safety & Security, Science & Technology, Safeguard & Verification Control that member states do not use civil installations with military goals (production of plutonium !) Control of the nuclear fuel in the whole fuel cycle * Fuel assemblies, rods, containers * (*Anti-neutrinos could play a role!) Distant & unexpected controls of the nuclear installations * Why IAEA is interested to antineutrino ? IAEA wants the « state of the art » methods for the future ! IAEA wants a feasibility study on antineutrinos Monitoring of the reactors with a Double-Chooz like detector ? Monitoring a country – new reactors “à la KamLAND” Double-Chooz-IAEA: Perform new antineutrino spectrum reactor (Mini-Inca +  -spectrometer) Use Double-Chooz near as a ‘prototype’ for nuclear reactor monitoring Other studies like large and very large underwater antineutrino detectors … Mini-Inca

G. Mention (PCC/APC) -NOW04- Double-Chooz sensitivity: can set sin 2 (2  13 )< , 90% C.L. (if  m 2 = eV 2 ) & can see sin 2 (2  13 )> , 3σ C.L. (if  m 2 = eV 2 ) Current limit: Chooz : sin 2 (2  13 )<0.2  discovery potential ! Technology / design well known (Chooz, BOREXINO, KamLAND,…)  few R&D needed : Gd loading (stability) + material compatibility (Started, to be completed in half a year) Collaboration: APC Paris, Saclay, Subatech, TU Munich, MPIK Heidelberg, Tubingen Univ. Hamburg Univ., Kurchatov, RAS Moscow, Univ. Alabama, Univ. Tennessee, Univ. Louisiana, Univ. Drexel, Argonne, + Italian groups discussing…  (maxi-)letter of intent (May 2004)  final proposal end of 2004 Approved in France. Our Construction starts in 2006 Start data taking in 2007 (far) & 2008 (near + far) Summary & outlook SiteData takingProp.Construction ?design in 2009 sin 2 (2  13 ) < 0.05 in 2011 sin 2 (2  13 ) < Far detector starts Near detector starts