Test

Document Sample
Test Powered By Docstoc
					q13 and the Double Chooz
       Experiment
       Prof. Charles Lane
        Drexel University
                      Outline
•   Status of neutrino oscillation and mixing
•   Questions that need answers
•   The Double Chooz experiment
•   beyond Double Chooz




    26 Apr 2005        UPenn               2
          Exciting times in neutrino
                   physics!




26 Apr 2005         UPenn         3
           Neutrino mass and mixing
• Neutrino interaction (or flavor) eigenstates
  (e, m, t) aren‟t necessarily mass eigenstates.
           ν e   U e1     U e2     U e3  ν1             3
                                                m
           ν μ    U μ1   U μ2     U μ3  ν 2 
          ν  U                     U τ3  ν 3 
                                                              2
           τ   τ1         U τ2                          1
• Neutrinos produced in a pure flavor
                                                              ?
  eigenstate propagate as a mixture of mass
  eigenstates.

  26 Apr 2005                 UPenn                       4
                Neutrino Oscillation
                     (2 flavor)
• illustrate basics with 2 flavor oscillation
• start with pure electron neutrinos

• propagate

• and see how many electron neutrinos are
  detected:


  26 Apr 2005          UPenn               5
                three types of oscillation
   e   1      0       0  c13          0    s13e  id  c12      s12   0  1 
                                                                         
   m    0    c23    s23  0           1       0   s12         c12   0  2 
     0
   t           s23   c23   s13e id
                                          0      c13  0           0    1  3 
                                                                                
                      qatm              q13, d                  qsol



• 12-mixing: solar neutrino oscillation 0.8
• 23-mixing: atmospheric neutrino osc. 1
• 13-mixing: still unknown q13, possible CP
  violation d0?


  26 Apr 2005                         UPenn                                   6
                    Results have been
                      accumulating
        natural    artificial
e       SNO       KamLAND
m     SuperK        K2K

• Neutrino oscillation seen with
  both “natural” neutrinos
  (solar/atmospheric) and
  “artificial” (reactor/accelerator)
• Both electron and muon
  neutrinos seen to oscillate,
  e→m and m→t
     26 Apr 2005                UPenn   7
              Using all the reactors in
                 Japan (arigato!)




26 Apr 2005            UPenn          8
              And a large underground
                     detector...
                     • 1kt of scintillator (544t
                       fiducial)
                     • 6.2%/sqrt(E) energy
                       resolution
                     • very low background,
                       2700mwe underground
                     • 0.6 events/day expected for
                       “no oscillation”

26 Apr 2005            UPenn             9
              What is seen:




26 Apr 2005      UPenn        10
              and the results
                   • KamLAND has
                     pinned down Dm122
                   • Solar + KamLAND
                     experiments have
                     greatly restricted
                     sin22q: close to
                     maximal mixing



26 Apr 2005       UPenn            11
                      Questions
• is there CP violation in the
  neutrino sector?
   – source of baryon asymmetry?
• neutrino mass hierarchy (123
  vs. 321 vs....)
• what value for neutrino masses
  (as opposed to Dm2)
• Are neutrinos Dirac particles or
  Majorana?


   26 Apr 2005            UPenn      12
                      Answers?
• is there CP violation in the       • reactor
  neutrino sector?                     q13,superbeams
   – source of baryon asymmetry?
• neutrino mass hierarchy (123       • superbeams
  vs. 321 vs....)
• what value for neutrino masses     • tritium b?
  (as opposed to Dm2)
• Are neutrinos Dirac particles or   • bb0
  Majorana?


   26 Apr 2005            UPenn               13
                 Constraining q13
              • current best limit: CHOOZ
                reactor experiment
                – 5t, 1km, 300mwe overburden
              • Dm2atm = 2×10-3 eV2 gives
              • sin2(2q13) < 0.2 for e→x from
                CHOOZ exclusion region
              • how to do better?


26 Apr 2005             UPenn               14
              Global fit for q13

                            • combine CHOOZ
                            limit with solar limit
                            • use SK Dm2atm range
                            •still get sin2(2q) <0.15
                            for center of Dm2 range




26 Apr 2005         UPenn                   15
              q13 seems in reach …
                      A Theoretician joke?

                                          Prediction
                                        27 models predications
                                        • 17 above 0.03
                                        • 4 between 0.01 and 0.03




                              Double Chooz 3y sensitivity




26 Apr 2005           UPenn                        16
                 How to measure q13?

• Accelerator based:
   – appearance experiment, me in a m beam.
   – P(me)  sin2(2q13)sin2(q23)sin2(Dm2atm L/4E)
• Reactor based:
   – disappearance experiment, small deficit from a large e
     flux:
   – P(ee) = 1 - sin2(2q13)sin2(Dm2atm L/4E)




   26 Apr 2005              UPenn                      17
          Accelerator Advantages &
               Disadvantages
• statistics: fewer events required
• signal is e production: need fine grain
  detector (with lots of mass, $$, time)
• flexibility of flavor, energy (m vs. m)
• background from e beam contamination
  (~1%), t events with t decay to e,
  NNp0 EM showers faking e events.
• Degeneracy of CP-violating & matter
  effects.

 26 Apr 2005        UPenn              18
              flavor changing oscillation:
               ambiguities, CP vs. matter
P(me) = (2c13s13s23)2sin2D31
+8c13s12s13s23(c12c23cosd-s12s13s23)cosD32sinD31sinD21
-8c13c12c23s12s13s23sindsinD32sinD31sinD21
+4s12c13(c12c23+s12s23s13-2c12c23s12s23s13cosd)sin2D21
-8c13s13s23(1-2s13)(aL/4E)cosD32sinD31
   where Dij= (mi2-mj2)L/(4E), and
   a = (constant)ne E  matter effects
Summation of terms give rise to ambiguities, it‟s hard to
  separate out effects: d vs. s13, sign(Dm13), q23 vs. p/2-q23

CP: a  -a, d  - d


     26 Apr 2005                     UPenn               19
              Ambiguity
                        • matter effects split
                          normal and
                          inverted hierarchy
                          areas.
                        • sin2q13 has a large
                          effect on how well
                          one can separate
                          the oscillation
                          terms
26 Apr 2005     UPenn                   20
                 Experimental risks
• If sin2q13 large
   – can resolve many ambiguities with off-axis
     “superbeam” accelerator experiments
   – optimal baselines and energies depend on value of
     sin2q13, better to know this in advance
   – lots of physics for superbeam experiments to pursue!
• If sin2q13 small (or zero)
   – effect of ambiguities small, but much harder to extract
     interesting physics
• Can the risk be reduced?

   26 Apr 2005              UPenn                     21
                Reactor neutrino
                  experiments
• low energy anti-neutrinos
  – L/E favorable for detecting oscillation
  – anti-neutrinos give event “doubles”; good
    background rejection
• copious anti-neutrino production from
  commercial power reactors
• pure , no flavor contamination
• neutrino flux completely isotropic, known
  to within ~few%....

  26 Apr 2005          UPenn                22
                     Double Chooz
                                             • return to Chooz site
                                             • differential
                               far
                                               measurement to
       near                                    reduce systematic
                                               errors
                                             • two identical
                                               detectors at different
Near detector   Far detector
                                               distances, 1km and
                                               100-200m

                         G. Mention (APC)


 26 Apr 2005                         UPenn                    23
                    Double Chooz people




Saclay, APC, Subatech, TUMunich, MPIK-Heidelberg, Tubingen Univ., Univ.
        Hamburg, Kurchatov, LNGS, Lousiana State, Argonne, Drexel,
        Univ. Alabama, Notre Dame, Kansas State, Univ. Tennessee


      26 Apr 2005                UPenn                      24
                               Near/Far

                      e                          e,m,t



                                D1 = 100-200 m              D2 = 1,050 m

                               Near detector                Far detector
• previous experiments limited by ~few% knowledge of reactor
  spectrum, ~3% systematic errors
• Near detector to measure unoscillated neutrino flux, compare with
  neutrino flux at far detector.
• A difficult experiment: must reduce systematic errors by a factor of
  ~3.5 compared to previous.
    26 Apr 2005                   UPenn                         25
                  good support helps!
                                • very good
                                  relations with
                                  local authorities
                                  and EdF!



• need close cooperation with
  EdF: detectors both “on-
  site”, need detailed burnup
  information.
    26 Apr 2005         UPenn                   26
                      Pure q13
• No d/CP effects in disappearance exp‟t.
• Negligible matter effects at L=1km
• P(ee) = 1 - sin2 2q13 sin2(Dm2atm L/4E)
              - cos4q13 sin2 2q12 sin2(Dm2sol L/4E)

                                Atmos.
      far
                                  Solar



  26 Apr 2005           UPenn                 27
                            The events
                                         proton-rich liquid scintillator
                                         is both a target and detector
e

               p   b+                    Add Gd to reduce neutron
                                         capture time, increase
                        n                capture energy

                                         ~30ms




                                                                    time
                            prompt                delayed
                            b+ signal:            n capture:
                            E - 0.8MeV           ~ 8MeV
     26 Apr 2005                 UPenn                         28
                          The challenge
                sin2(2q13)=0.04           sin2(2q13)=0.04
                sin2(2q13)=0.1            sin2(2q13)=0.1
                sin2(2q13)=0.2            sin2(2q13)=0.2




• signature of q13: a small spectral distortion
• must reduce errors to get a good measurement

  26 Apr 2005                     UPenn         29
                        Improvements
• Statistical error: CHOOZ: 2.8%, ~2700 events
   – increase fiducial, luminosity, exposure: 0.5%, >40,000 events
• Systematic errors: CHOOZ: 2.5%, neutrino flux and cross-section
   – near detector determination of spectrum
   – same cross-section, reactor power, spectrum for both detectors
   – use same detector design, scintillator mix (target mass)
• Backgrounds
   – CHOOZ: S/N=25/1, Double Chooz goal: 100/1
   – main concern is muon-induced correlated backgrounds
   – far detector overburden ~300mwe
   – near detector overburden ~60mwe (but more signal too)
   – improve veto efficiency, add large muon tracking outer veto
   – reactor ON/OFF, power modulation

   26 Apr 2005                   UPenn                        30
                            Near and Far sites




          3,5m (under the crane)
                                                            250 m
                                                    125 m




   Muon
   Veto                            Buffer

   Gamma Catcher           Target

26 Apr 2005                                 UPenn           31
              Detector Design
                          • inner 12t Gd-loaded
                            scintillator target
                          • non-loaded
                            scintillator g-catcher
                          • non-scintillating
                            buffer, with
                          • 200 PMTs (8”)
                          • inner veto
                          • 15cm iron shielding

26 Apr 2005       UPenn                    32
                                Clone that detector!
                                                         e • neutrons can
            b+             b+                     100%
  Gd                                                         diffuse into or
  loaded    Gd        Gd                                     out of target
                                                           • neutron spill
                           H         H
                                                             in/out hard to
                 b+             b+
unloaded                                 0%                  determine with
                                                             <1% error
                                                           • use identical
                                                             inner vessels for
                                                             two detectors to
           detected   not detected                           “null out” this
           as  event as  event                             effect.
                                                           • still some affect
                                                             from different
                                                             1/r2, etc.


           26 Apr 2005                    UPenn                      33
              Squeezing down errors
                           @CHOOZ: R = 1.01  2.8%(stat)2.7%(syst)


                                        – Statistical error –

                                                 CHOOZ                 Double Chooz
              Target volume                       5,55 m3                12,67 m3
              Target composition               6,77 1028 H/m3          6,82 1028 H/m3
              Data taking period                Few months             3-5 years
                                                                  CHOOZ-far : 60 000/3 y
              Event rate                           2700
                                                                  CHOOZ-near: >3 106/3 y
              Statistical error                    2,7%                  0,4%

                                   Luminosity incerase L = Dt x P(GW) x Np


                 – Systematic error –

                              Improve the detector concept
                              Two identical detectors  towards
                                 σrelative~0,6%
                              Careful backgrounds control  error<1%
26 Apr 2005                            UPenn                            34
                Relative errors: reactor
                                                              2 identical detector
                                                   Future
 systematics        Error type           CHOOZ                  Low background
                                                 Experiment

                 Flux, cross section      1.9%       -              O(0.1%)

                  Thermal power           0.7%       -              O(0.1%)
  Reactor            E/Fission            0.6%       -              O(0.1%)

                                         2.1%       -              O(0.1%)



• most reactor-based relative errors will
  cancel out in a differential measurement


  26 Apr 2005                          UPenn                          35
                Relative errors: detector
•Solid angle
     - Distance measured within 10cm + Monitoring of the  source barycenter …

• Target volume
     - CHOOZ : 0.3% [simple measurement]
     - Goal ~0.2% [same apparatus for both detectors] - Not trivial …

• Density
    - 0.1% achievable, but accurate temperature control mandatory

• H/C ratio & Gd concentration
    - Absolute measurement is difficult : 1% error in CHOOZ
     - Plan: use the same batch to fill both detectors

• Boundary effect at the inner vessel interface (spill in/out)
    - Neutron transport slightly different due to solid angle effect
     - MC study to be done to check that it is negligible

• Live time to be measured accurately by several methods
  26 Apr 2005                            UPenn                           36
                Relative errors: detector
                                                         Sim.
                                               Future            2 identical detector
                                                        Monte-
systematics        Error type           CHOOZ Experimen           Low backgrounds
                                                         Carlo
                                                  t
               Scintillator density      0.3%    0.3%                  O(0.1%)

                       %H                1.2%    1.2%                  O(0.1%)

                 Target volume           0.3%    0.2%                   0.2%
 Detector
              « Spill in/out » effect    1.0%    1.0%     X            O(0.1%)

                    Live time             ?     0.25%                  0.25%

 • filling both detectors with one batch of scintillator will
   greatly reduce some systematics (then seal detectors to
   keep them the same)
 • need some calibrations, MC to check for differences in
   spill in/out
 • live time one of the easiest things to measure accurately,
   0.25% likely an overestimate (my opinion)
    26 Apr 2005                UPenn                      37
                       Relative errors: analysis
•   CHOOZ had 1.5% error from analysis                                        e+
     – 7 analysis cuts, 70% efficiency
•   Double Chooz goal: 0.3% error, fewer cuts needed as
    a result of detector design
                                            non-scintillating buffer
     – neutron energy                       reduces low energy
     – neutron capture time Dt              background, allows
     – perhaps b+,n distance (if needed)    relaxing positron energy
                                                                               n
                                            cut, position cuts.
                                             improved calibrations and
                                             light yield help too.




                                                                              Dt




         26 Apr 2005                       UPenn                         38
                        Signal vs. Background
                                             E>1MeV
                                                              n
e            511keV2

                   b+
          p                                               =8MeV

                        n                      uncorrelated

                                             fast n
                   =8MeV



                                    DEvis > 1MeV


                                      correlated
                            also b decay + n            =8MeV

     26 Apr 2005                     UPenn                         39
                     CHOOZ Backgrounds
• Large singles rate
    – PMTs in scintillator
    – Vertex cut, positron energy cut
      reduced background, at cost of
      increased systematic error
    – New design with buffer volume will
      greatly reduce singles rate
• Reactor OFF data
    – Allowed direct measurement of
      correlated backgrounds
    – Consistent with other analysis
      methods for eliminating backgrounds
• Known environment for future
  experiment                                  Eur.Phys.J. C27 (2003) 331-374


       26 Apr 2005                    UPenn                       40
                        Background summary
- Chooz                (300 mwe)                             5.5 m3, Noise/Signal ~ 4%
     - Correlated events (neutrons):
            Chooz : ~1 recoil proton per day

- Double Chooz-Far               (300 mwe)                   12.7 m3, Signal  2.4

     - Uncorrelated (b,g + n capt. on Gd): S3 & N/3  can be subtracted
     - Correlated events (neutrons):
            Goal <1 events per day + known spectrum  N/S<~1%
     - Correlated events (cosmogenics)

- Double Chooz-near              (60 mwe)                    12.7 m3, Signal  30-50 SFAR

     - Key advantage: Dnear~150 m  Signal  ~30-50
     - Uncorrelated: Chooz-Far backgrounds  50  can be subtracted
     - Correlated events: Chooz-Far  <30  N/S < 1%
     - Correlated events (cosmogenics)


(not a comprehensive list...)

         26 Apr 2005                            UPenn                         41
              What does a reduction in
                systematics buy?
                                    • unfortunately,
                                      decreasing
                                      systematics is not
                                      as simple as
Double Chooz
                                      “scaling up” an
    Goal
                                      experiment
                                    • if q13 is very
                                      small, Double
                                      Chooz is a good
                                      step toward a
                                      detector that can
                   Original Chooz
                                      measure it.
                   Detector Error
26 Apr 2005             UPenn                42
                                  Work in Progress
•   US Proposal submitted in Fall 2004
•   PMTs
      –   Testing radioactivity
      –   Mounting systems
•   Electronics/HV
      –   Prototype designs are under study
      –   DAQ system is under design
•   Calibration
      –   Fiber Optic/LED system
      –   Articulated arm vs. Rope-and-Pulley development
      –   Wire driven Guide Tubes for Gamma Catcher
      –   Radioactive source development
•   Simulation
      –   Full G4 Detector Simulation (derivative of KamLand)
            •   Complete optical properties
            •   All Chemical Properties
      –   Muon/fast neutron in G4 and FLUKA
      –   Feeding back the R&D into the simulation effort
•   Non-Proliferation
      –   Collaboration with LLNL and IAEA
      –   Interest in monitoring reactor power and fuel composition




    26 Apr 2005                               UPenn                   43
                     Double Chooz Status:
                          (Europe)
• EDF has agreed to the project
    – Allow use of the original laboratory
    – Agreed to location for near laboratory (150-200 meters from core)
• French funding agency has approved the project
    – Provide ½ the funding for detector construction
    – Agreed to fund the construction of the near laboratory
          • Awaiting complete engineering analysis and costs from EdF
    – Contracts for prototype construction are already under negotiations for
      bids
• MPI-Heidelberg is providing independent funding for Liquid
  Scintillator development and production
• Germany still has other institutions seeking „normal‟ funding
    – 5 year cycle but they are in the queue
• Italy is working on LS but has no funding yet
    – Rumors that the canceled BTeV may free up Italian money
• Russians have agreed to produce radioactive sources but little money is
  expected
    26 Apr 2005                         UPenn                           44
                Double Chooz Status (U.S.)
• Submitted proposal to DOE in October „04
   – $4.8M over 3 years for total project
   – Already secured forward funding of $3M
   – DOE has decided to not decide (for now)
        • Establishing neutrino SAG
        • Double Chooz Construction Proposal competes with R&D
          requests from Braidwood and Daya Bay...
        • decision within a few months, we hope
• US groups are continuing to finalize design work
  on expectation of approval
• New groups are continuing to join
   – Recent interest from groups at Los Alamos and
     Livermore
  26 Apr 2005                  UPenn                      45
                      Expected Sensitivity
                          2007-2012

• Far Detector to start in 2007
• Near detector follows 16                sys=2.5%
  months later
• Double Chooz can surpass
  the original Chooz bound in
  6 months, with just a single
  detector
                                                                                     sys=0.6%
                                          Far detector   Far & Near detectors
                                              only            together




                                   05/2007 05/2008 05/2009 05/2010


                      90% C.L. contour if sin2(2q13)=0
          Dm2atm = 2.810-3 eV2 assumed known at 20% by MINOS


       26 Apr 2005                UPenn                                         46
                What comes after
                Double Chooz?
• More ambitious reactor q13 experiments
  – Dia Bay/Braidwood, q13 > 0.01-0.03 ?
  – Angra, q13 > 0.01 (shape only)?
  – further reductions in systematic error needed
• Off-axis “superbeam” accelerator
  experiments
  – resolve mass hierarchy, CP violation, etc.
  – T2K, FNAL...
  – it helps if you know where to look...

  26 Apr 2005           UPenn                47
                    Reactor experiments

                                  Double Chooz
              Braidwood
                                                 Daya bay



                                                            Kaska




                          Angra




26 Apr 2005                       UPenn               48
                             Braidwood, Daya Bay, Kaska and Angra
Two reactor cores
                                                    Braidwood               Four reactor cores
                                                                                                                                      Daya bay
P=2 x 3.6 GWth                                                              P=4 x 2.9 = 1.6 GWth + two 6 GWth units in 2011
Civil construction                                                          Civil construction
Flat topology                                                               Near: 1 km tunnel + laboratory
Near & Far: 120m shafts (10m diameter) + laboratories (25-35 M$)            Far: 2 km tunnel + laboratory
Two 50 tons detectors                                                       ~10 tons detector modules
Near: 25-50 tons – 300 m – 450 mwe                                          Near: 25 tons - 300 m – 200 mwe
Far: 25-50 tons – 1.5-1.8 km - 450 mwe                                      Far: 50 tons - 1.5-1.8 km - 700 mwe
Movable detector (move on the surface, lift with crane)                     Movable detector concept
3 years Sensitivity                                                         Sensitivity
0.5% systematic error                                                       0.4% systematic error, sin2(2q13) < ~ 0.01 (90% C.L.) ?
No signal: sin2(2q13) < 0.01 (90% C.L.)                                     Prospects (not yet approved)
Prospects (not yet approved)                                                2004-05: R&D, 2006-07: Construction
Construction in 39 month - running in 2009. Cost ~70 M$                     1 Near detector running in 2008
Geological studies ongoing                                                  Geological & safety studies ongoing


Seven reactor cores
                                                         Kaska              Single reactor core
                                                                                                                                         Angra
P=24.3 GWth                                                                 P=4.1 GWth , A new core is being built (2006)
2 near detector mandatory                                                   Civil construction
Civil construction                                                          Near: 6x6x60m tunnel + 10x10x12m exp. hall
2 Near: ~70 m 6m shafts + laboratories                                      Far: 6x6x450m tunnel + 10x10x12m exp. hall
Far: ~250 m 6m shaft + laboratory                                           + emergency shafts
Multiple detectors                                                          Two >100 tons detector
2 Near: 8 tons – 300-400 m – 100 mwe                                        Near: 300 m – 50 mwe ?
Far: 8 tons - 1.3-1.8 km - 500 mwe                                          Far: 1.35 km - 600 mwe
Sensitivity                                                                 Non movable detectors concept
0.5% systematic error                                                       Sensitivity
sin2(2q13) < 0.025 (90% C.L.)                                               5 years  >103 GWth.t.y , sin2(2q13) < 0.01 (90% C.L.)
Prospects (not yet approved)                                                1% systematic error, Shape only analysis possible
2004-05: R&D, 2006-07: Construction. Running in 2008. Cost ~20 M$           Project of second generaration
Geological studies ongoing – Prototype to be built for R&D.



           26 Apr 2005                                              UPenn                                                   49
                  2nd Generation: Angra (Brazil)
                  Argonne + Brazil : CBPF, UNICAMP, USP, PUC-RIO

Single reactor core
    P=4.1 GWth
    A new core is being built (2006)


Civil construction
    Near: 6x6x60m tunnel + 10x10x12m exp. hall
    Far: 6x6x450m tunnel + 10x10x12m exp. hall
    + emergency shafts


Two >100 tons detector
    Near: 300 m – 50 mwe ?
    Far: 1.35 km - 600 mwe
    Non movable detectors concept


Sensitivity
    5 years  >103 GWth.t.y
    sin2(2q13) < 0.01 (90% C.L.)
    1% systematic error
    Shape only analysis                Angra dos Reis, RJ - Brazil / 23-25 February 2005
         26 Apr 2005                        UPenn                             50
                 Double Chooz + Off-Axis
                      neutrino beam
• Double Chooz complementary
  to off-axis neutrino beam                                         mass heirarchy
  experiments.                                                      resolved @ 2

• A positive signal within the
  Double Chooz range would
  signify a very rich program at
  the accelerator measurements




                                                                                        from M. Shaevitz
• A null result would imply a
  difficult path
• Double Chooz is the only
  experiment which can provide
  such a direct result in a short
  time period (~3-4 years)
                                    Sensitivity regions for resolving the Mass Hierarchy at
                                                      2 (with Proton Driver)

   26 Apr 2005                      UPenn                               51
                                Conclusions (1)
 A new reactor neutrino experiment could provide an evidence of the
  oscillation in the (1,3) neutrino sector by 2009

 Reactor & accelerator programs provide independent and complementary
  measurements of q13.

  Reactor experiments won’t replace the rich accelerator program. However,
  a preliminary value of q13 will help to design the best CP-d detector:

           P( m   e )  P( m   e )             sin( d )         1
   Acp                                     0.1                                 ( stat )  ( syst )
           P( m   e )  P( m   e )           sin( 2q13 ) sin( 2q13 ) N 1/ 2



 Several projects of reactor experiment & strong world momentum
    First generation : sensitivity sin2(2q13)~0.015-0.03 - Rate + Shape
       Motionless detectors:      Double Chooz, KASKA
       Movable detectors:         Daya-bay, Braidwood
    Second generation : sensitivity sin2(2q13)<~0.01 - Shape only (>103 GWth.tons.year):
       Motionless detectors:      Angra



           26 Apr 2005                         UPenn                                     52
                          Conclusions (2)
 Double CHOOZ sensitivity: sin2(2q13)<0.02-0.03, 90% C.L
  (Dm2 = (2.0-2.8)10-3 eV2)
  Current limit: CHOOZ : sin2(2q13)<0.2  excellent discovery potential !

 Technology / design well known (CHOOZ, BOREXINO, KamLAND, …)

 Well known site, good cooperation with EdF

 Collaboration: a strong collaboration with experience with Chooz, Palo
  Verde, KamLAND, Borexino,...

 Our Goal for Double CHOOZ:
     Construction starts end 2006
     Start data taking in 2007 (far) & 2008 (near + far)
                                        Far detector starts             Near detector starts


         2003        2004       2005       2006         2007        2008          2009
         Site        Proposal          & design        Construction ?        Data taking

       26 Apr 2005                             UPenn                                       53
fin
                    Stability
• Reducing systematic errors is a challenge
• Build identical detectors, then closely
  monitor stability to keep them identical
   – Gd scintillator must be stable over 3-5
     years
• Simple design: easier to understand fully,
  calibrate and monitor (and explain).


  26 Apr 2005         UPenn              55
            Long Term Liquid Scintillator
                     Stability
• Gd doping has resulted in poor
  stablity of liquid Scintillator
    – Palo Verde had problems with
      precipitation/condensation
          • Mystical fix with water vapor
    – Chooz saw a decay of attenuation
      length
• Heidelberg and LNGS
  (LENS/Borexino) have been
  working for the last 3-5 years to
  understand these effects
    – Simple dissolved Gd solutions are
      very sensitive to pH
    – Attempting to bind Gd into the
      chemical structure of the liquid
                                                Eur.Phys.J. C27 (2003) 331-374


    26 Apr 2005                         UPenn                     56
                   Gd Doped Scintillator Aging
                             Tests
                                                           Gd-Acac Heidelberg                            Gd-CBX (test in Saclay)
•   20C - long period test                                     Gd(acac)3 in pure PXE (1 g/l)
     –
                                                        0,08
        All Gd-CBX,Acac, Dmp are stable                                                 0 days
                                                                                        62 days
     –
                                                        0,07
        Yb sample stable for 4.5 years                                                  210 days




                                           Absorbance
                                                        0,06
       (small sample)
                                                        0,05
     – In sample stable for 1.5 years
                                                        0,04
       (2 liters, 1 year meas. @LNGS)                                                                             Gd-CBX
                                                        0,03
                                                           400 420 440 460 480 500 520 540 560 580 600
                                                                       wavelength [nm]




• High Concentration Test
     – LENS R&D: Yb, Gd, In  2 In-sampled loaded at 5% measured for 1 year @
       LNGS and found stable (10-20% error)
     – 6 month 1% Gd-CBX Stable  work in progress
• High Temperature Test
     – 40C for several weeks to accelerate aging
     – Still under investigation
• Next Step: large scale production and stability test

         26 Apr 2005                      UPenn                                                                 57
                     Neutron Induced Background
•   Cosmic muons create fast neutrons                                            μ                                 μ
     –   Spallation in the rock surrounding the detector
                                                                                      μ capture
     –   Muon capture in the detector materials
•   Fast neutron slows down by scattering into the                                       n from m
                                                                           Recoil p
    scintillator (depositing energy) and is later                                        capture
    captured on Gd !                                                                       Gd
•   Full simulation – Geant + Fluka
     –   Old Chooz configuration: 300 m.w.e. 31hours –
         to validate MC                                                            Gd
           •   Simulated: Nb<1.6 evts/day (90% C.L.)
                                                                            n capture Recoil p
           •   Measured in-situ: Nb=1.1 evts/day
                                                                             on Gd
     –   Double Chooz configuration:
           •   338 106 μ tracked – 580 103 neutrons tracked                                   Spallation fast
           •   1 neutron created a background event                                              neutron
•   Far detector expectation:
     –   Nb<0.5 evt/day (90% C.L.)
•   Near detector expectation:                                    An outer muon veto will surround ; this is a gas-
     –   Nb<3.2 evts/day (90%C.L.)                                filled proportional chambers with a resistive wire
                                                                  for charge division. (Atlas muon chambers design).




         26 Apr 2005                                      UPenn                                 58
                         β-neutron Cascades
                           (Cosmogenics)
  m crossing the detector
Likely to be seen by the Veto
                                            8He     9Li   11Li




                                                       β decayed followed
                                                  by n emission within 200 ms !
                                                         (not veto-able)




         μ interaction
            on 12C




                                        KamLAND data useful for
     26 Apr 2005                UPenn   estimating rates 59

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:15
posted:8/11/2011
language:English
pages:59