The DoubleChooz project of experiment for the last undetermined mixing angle 13

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The Double-Chooz project of experiment for the
last undetermined mixing angle ?13
Thierry Lasserre (Saclay APC) H. de Kerret
(APC) 09/02/04, Paris - Chicago
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The Chooz site
Near site D100-200 m, overburden 50-80 mwe Far
site D1.1 km, overburden 300 mwe former
experimental hall
2x12.5 tons, D1100-200m, D21050m. Sensitivity
3 years ? sin2(2?13) lt 0.03
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CHOOZ-Far ready to be used again!
Photo taken in September 2003
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CHOOZ-Far detector (12.7m3 fiducial, preliminary)
Shielding main tank of 0.15m of steel
7 m
Gamma catcher inside Acrylic Vessel Thickness
0.6m
Target cylinder (f 2.4m, h 2.8m) filled with
0.1Gd loaded liquid scintillator (12.7 Tons)
7 m
Buffer inside non-transparent vessel equipped
with photodetectors
7 m
7 m
Muons VETO of scintillating oil Thickness 0.6 m
existing pit
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CHOOZ-Near
Near detector _at_100-200 m from the nuclear
cores in discussion with EDF
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CHOOZ-Near new Laboratory
10-15 m
Dense material
5- 15 m
Other possibility bloc of concrete (d2.4) piled
up !
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Improve CHOOZ is difficult !(Part I)
_at_CHOOZ R 1.01 ? 2.8(stat)?2.7(syst)

• Increase the luminosity L ?t x P(GW) x Vtarget
• CHOOZ 2700 events ? sstat 2.7
• Project Reactor/?13 with 40 000 evts ?sstat 0.5
  
• _at_1.05 km, 50 kevts ? 10 tons (scint. PXE) x 8.4
  GWth x 3 years
• Detector size ? CHOOZ 5 t
• ? Double-Chooz 12.5 t
• Data taking time (3 ans ? 5 ans) with high
  efficiency
• Choice of the scintillator
• Pure PXE 0.1 Gd or 20 PC/PXE 0.1 Gd
  80 Min. oil
• Mainly driven by gd loaded scintillator long
  term stability
• Mixture 80 Min. oil 20 PXE ? 30 more free
  protons!

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Improve CHOOZ is difficult !(Part II)

• Decrease systematic errors
• Systematic errors for CHOOZ ssys 2.8
• 1) Improve the detector design for ?13
  measurement
• 2) 2 identical detectors ? towards srelative sys
  O(0.1)
• Strategy gain a factor /10 to get srel
  detector1-detector2 lt 0.8
• Backgrounds S/N gt 100 ? error lt 1

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Relative Normalisation detector

• Solid angle
• - distance measured _at_10cm
• - To be checked again
• Target volume
• - _at_CHOOZ 0.3 simple measurement
• - Goal 0.2 same apparatus for both detectors
  - Not trivial
• Density
• - 0.1 achievable
• - Accurate temperature control mandatory
• H/C Gd concentration
• - Absolute measurement is difficult 1 error
  _at_CHOOZ
• - Plan use the same batch to fill both
  detectors
• Edge effect (spill in/out)
• - Neutronic slightly different due to solid
  angle effect
• - MC study to be done to check that it is
  negligible

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Detector induced systematics
M. Apollonio et. al., Eur.Phys.J. C27 (2003)
331-374
A single scintillator batch will be prepared to
fill both detectors with the same apparatus
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Relative Normalisation Analysis

• _at_CHOOZ
• - 7 analysis cuts
• - Efficiency 70 1.5 systematic
• Sélection cuts
• - positron energy energy
  threshold
• - e position/géode (30cm) position
  reconstruction
• - neutron energy energy cut - calibration
• - n pos./géode (30 cm) position
  reconstruction
• - distance e - n position reconstruction
• - ?t e - n neutron capture on Gd
• - n multiplicity level of accidental
  background
• Goal Double-CHOOZ
• - 2 to 3 analysis cut
• Sélection cuts
• - neutron energy
• (- distance e - n ) level of accidentals

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? selection cuts systematics _at_Chooz I 

M. Apollonio et. al., Eur.Phys.J. C27 (2003)
331-374
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? selection cuts systematics goal

• Goal Double-CHOOZ
• - Spatial effect Negligible ? Check
• - Target volume 0.1 - 0.2
• - density 0.1
• - H/C Gd 0.1
• - Edge effects neutronics 2nd order
  effect ? Check ...
• - Analysis cuts 0.2 0.1
• - Live time lt0.2
• ----------------------
• 0.5

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Backgrounds Estimates

• CHOOZ N/S 4
• Double-CHOOZ-Far (300 mwe) 12.7 tons ? Signal
  x 3
• Modification of the detector design ? expensive
• Uncorrelated N/S(chooz) 4 Double-Chooz
  Sx3 N/3 ? lt 0.5
• Correlated events N/S lt 1
• CHOOZ lt1 recoil proton per day
• Double-CHOOZ liquid active buffer 30cm ? 0.3
  events per day
• - Double-CHOOZ-near (50 mwe) Signal x 50-100
  S(CHOOZ-Far)
• -Key advantage Dnear 100-200m ? Signal x
  50-100 !
• -Uncorrelated CHOOZ-Far backgrounds x 50 ?
  N/S lt 1
• -Correlated events CHOOZ-Far x lt30 ? N/S lt
  1

Double-CHOOZ background working group TUM, PCC,
Saclay, Milano
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Neutron Induced Background
Technische Universitaet Muenchen, Universitaet
Tuebingen

• Simulation of the transport of muon induced
  neutrons with Geant4
• Neutron production in the surrounding rock by
  cosmic ray muons and their transport simulated
  with Fluka
• Ongoing work

Surrounded by 100 mwe rock shielding
Background working group internal external
bkgs under study
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Gd Liquid scintillator completion of the RD!

• LENS RD ? new metal ß-diketone molecule (MPIK)
• Stable 0.1 Gd-Acac (few months)
• Baseline receipie 80 mineral oil 20 PXE
  Fluors wavelenght shifters
• In-loaded scintillators (0.1 , 5 loading) are
  counting _at_Gran Sasso
• Spare stable receipies available (MPIK, INFN/LNGS)

Stability 0,1 Gd in PXE
3Gd
Gd-Acac molecule

• Completion of the RD first half of 2004
• Choice of the final scintillator
• Stability Material compatibility ? Aging tests
  (MPIK, Saclay)

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Gd Liquid scintillator tests in Saclay

• Goal 1/ Test the LONG term stability of the
  scintillator
• 2/ Test the material compatibility with acrylic,
  glue, ...
• ? Towards the desgin of the acrylic vessels
• Tight stainless steel boxes flushed with N2 20-
  130cl quartz cuvettes
• Aeging test ? scintillator temperature 50
  degrees
• Systematic periodic photospectrometer absorbance
  measurements

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Full detector simulationPCC APC, Kurchatov