A New Experiment To Measure 13

1
A New Experiment To Measure ?13

• David Reyna
• Argonne National Laboratory

2
3 Flavor Mixing Matrix

• CKM Matrix

• MNS Matrix

3
Mixing Angles
Matrix Components 3 Euler Angles (?12 ?13
?23) 1 CP phase (d) (2 Majorana Phases)
Solar (?e??x)
Atmospheric (?µ??x)
The Next Big Thing?
4
Current Experiments
Unconfirmed observation by LSND, currently being
investigated by MiniBooNE. Would require the
existence of sterile neutrinos or CPT violation.
Measured by Super-K and confirmed by Soudan2 and
K2K.
First observed by Ray Davis and collaborators.
Measured by Super-K, SNO and KamLAND.
5
?m2 (aka LSND problem)

• For 3 ? only 2 independent mass differences
• Mass hierarchy unknown

Normal
Inverted
m2
m3
m1
?m2
(?m2atm 2 x 10-3 eV2)
m2
m3
m1
(?m2solar 7 x 10-5 eV2)
6
Current q13 Bound
Current Limits are set by experiments which were
not trying to measure ?13 Optimization of the
experiments for this goal was never done
In currently allowed range (?m2 1.3-3 x 10-3
eV2) sin2(2?13) lt 0.19 _at_ 90 CL
7
How to Measure q13

• Appearance measurement
• Accelerator measurements look for small ?e
  appearance in ?µ beam
• P(nm?ne) sin2(2q13)sin2(q23)sin2(Dm2atm L/4E)
• Disappearance measurement
• Reactor measurements look for small ?e
  disappearance from large isotropic flux
• P(ne?ne) 1 - sin2(2q13)sin2(Dm2atm L/4E)

8
Accelerator Difficulties

• Signature is electron appearance
• Requires massive detector with fine granularity
  (be able to distinguish e from P)
• Backgrounds
• ne in the beam, (1, from m, K?e3, K0e3)
• Fake ne from nt, t?e, (at high energy)
• Showers which look like es, particularly
  
  nN?nNp0, p0?gg
• Measurement has degeneracies due to cp-violation
  and matter effects

9
ne Appearance in a nm beam
P(nmgne) (2c13s13s23)2 sin2F31
8c13s12s13s23(c12c23cosd-s12s13s23)cosF32sinF31s
inF21 -8c13c12c23s12 s13s23sind
sinF32sinF31sinF21 4s12c13(c12c23s12s23s13-2c12
c23s12s23s13cosd)sin2F21 -8c13s13s23(1-2s13
)(aL/4E)cosF32sinF31
2
l CP violating
2
2
2
2
2
2
2
2
2
2
2
2
a constant X neE
CP ag-a, dg-d
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Understanding the Degeneracy
Minakata and Nunokawa, hep-ph/0108085
cosd

• d

• There are 2 Observables
• P(nm?ne)
• P(nm ?ne)
• Interpretation in terms of sin22q13, d and sign
  of Dm223 depends on the value of these parameters
  and on the conditions of the experiment L and E

sind
sin22q13
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Experimental Solutions

• If ?13 is large, the degeneracy can be broken
  with Off-Axis measurements
• Measure both ? and anti-? rates
• Multiple experiments with different baselines and
  different energies
• Will yield a rich physics program for cp-phase
  and mass hierarchy
• If ?13 is zero, degeneracies collapse but theres
  no attainable physics gain
• Big cost - big risk

12
The Reactor Measurement

• P(ne?ne) 1 - sin2 2q13 sin2(Dm2atm L/4E)
  - cos4q13 sin2 2q12 sin2(Dm2sol
  L/4E)

solar
No CP-violation in a disappearance
measurement Distance (1Km) is too short for
matter effects
P
atmospheric
L/E(km/MeV)
13
Previous Reactor Measurements

• All measure the same energy spectrum.
• Previous experiments used single detector and
  were limited by 3 uncertainty in reactor power.
• KamLAND is first to see positive evidence of
  oscillation.
• Future experiments propose 2 detectors of 10-100
  tons (not kilotons).

KamLAND sees a 40 deficit/shape at 200km related
to Dm212 Search for a 1-5 deficit/shape at 1 km
related to Dm213
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How to Detect a ne Event
15
Reactor ns

• Reactors provide a fairly steady flux of 1-10
  MeV ns
• Neutrino energy carried by positron
• E? Ee 0.8 MeV
• Adding Gd moves n-capture peak from 2.2 MeV
  to 8 MeV and reduces capture time to 10µs

from Palo Verde
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The Double Chooz Concept
?e
?e,?,?
D2 1,050 m
D1 100-200 m
8.4 GWth Chooz PWR power station
Near detector
Far detector

• Measure neutrino flux before and after
  oscillation
• Measure difference from 1/r2 dependence
• Improve detector design to reduce systematics

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Who is Double Chooz?
Saclay, APC, Subatech, TUMunich, MPIK-Heidelberg,
Tubingen Univ., Univ. Hamburg, Kurchatov, LNGS,
Lousiana State, Argonne, Drexel Univ. Alabama,
Univ. Notre Dame, Kansas State, Univ. Tennessee
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EdF Has Approved Access to All Sites
19
Far Near Sites

• 60 m.w.e. overburden
• 12 m compacted earth
• 3 meter high density material

DAPNIA
20
Reactor Challenges

• Long term stability (Liquid Scintillator)
• Chooz/Palo Verde were few month exps
• Next generation must be 3-5 years
• Backgrounds
• Chooz measured 10 with reactor off
• Unlikely to duplicate reactor off data
• Systematic Error Control
• Consistency of mechanical construction
• Previous exps were 2-3 (excluding reactor)
• Needs to be 1 or less

21
Long Term Stability (Liquid Scintillator)

• Gd doping has resulted in poor stablity of liquid
  Scintillator
• Palo Verde had problems with precipitation/condens
  ation
• Mystical fix with water vapor
• Chooz saw a very rapid 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
22
Gd doped scintillator

• Solvant 20 PXE 80 Dodecane
• Gd loading 3 recipes developed _at_Heidelberg
  LNGS
• Gd-CBX
• Good stability _at_20oC
• Suitable baseline End of development
• Gd-Acac
• Good stability _at_20oC
• Low solubility in PXE ? warning
• Difficult to purify
• Gd-Dmp

3Gd
LY8000 ?/MeV L 5-10 m
6 g/l PPO 20 mg/l BisMSB
Gd-Acac Gd-Dmp
Gd-Carboxylate
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Gd Doped Scintillator Aging Tests
Gd-Acac Heidelberg
Gd-CBX (test in Saclay)

• 20?C - long period test
• All Gd-CBX,Acac, Dmp are stable
• Yb sample stable since 4,5 years
• (small sample)
• In sample stable since 1,5 years
• (2 liters, 1 year meas. _at_LNGS)

Gd-CBX

• High Concentration Test
• LENS RD Yb, Gd, In ? 2 In-sampled loaded at 5
  measured for 1 year _at_ 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

24
Backgrounds

• Accidental Backgrounds
• Mainly at Low E
• Best measurement from Borexino(CTF)
• Must reduce few MeV radioactive sources and
  thermal neutrons
• Correlated Backgrounds
• Mainly from cosmic muons
• Best measurements from KamLAND but hard to
  extrapolate to shallow depth
• Must reduce overall muon rate and attempt to veto
  background candidates

accidental background (uncorrelated)
correlated background
?-n cascades
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Neutron Induced Background

• Cosmic muons create fast neutrons
• Spallation in the rock surrounding the detector
• Muon capture in the detector materials
• Fast neutron slows down by scattering into the
  scintillator (depositing energy) and is later
  captured on Gd !
• Full simulation Geant Fluka
• Old Chooz configuration 300 m.w.e. 31hours to
  validate MC
• Simulated Nblt1.6 evts/day (90 C.L.)
• Measured in-situ Nb1.1 evts/day
• Double-Chooz configuration
• 338 106 µ tracked 580 103 neutrons tracked
• 1 neutron created a background event
• Far detector expectation Nblt0.5 evt/day
  (90 C.L.)
• Near detector expectation Nblt3.2 evts/day
  (90C.L.)

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ß-neutron Cascades (Cosmogenics)
? crossing the detector Likely to be seen by the
Veto
8He 9Li 11Li
ß decayed followed by n emission within 200 ms
! (not veto-able)
µ interaction on 12C
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Chooz Backgrounds

• Large singles rate
• PMT glass in scintillator
• Used vertex cut to reduce effect but with
  increased systematic error
• New detector design will eliminate this effect
• Took data with all reactors off
• 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
28
Background Estimates

• 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 x
  2.4
• Uncorrelated (?,? n capt. on Gd) Sx3 N/3 ?
  can be subtracted
• Correlated events (neutrons)
• Goal lt1 events per day known spectrum ?
  N/Slt1
• Correlated events (cosmogenics)
• Double-Chooz-near (60 mwe) 12.7 m3, Signal x
  30-50 SFAR
• Key advantage Dnear150 m ? Signal x 30-50
• Uncorrelated Chooz-Far backgrounds x 50 ? can be
  subtracted
• Correlated events Chooz-Far x lt30 ? N/S lt 1
• Correlated events (cosmogenics)
• (but not a comprehensive list of backgrounds )

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Additional Outer Veto at Near Detector
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New detector design
7 m
7 m
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Systematic Breakdown
25 _at_ 15m Signal/Background 2.2 _at_ 40m 0.7 _at_
95m
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Detector Relative Comparison

• Solid angle
• Distance measured _at_10cm Monitoring of the ?
  source barycenter
• Target volume
• _at_CHOOZ 0.3 simple measurement
• Goal 0.2 same apparatus for both detectors
• Test - scale 1 - in progress
• Density
• 0.1 achievable, but accurate temperature control
  mandatory
• H/C ratio Gd concentration
• Absolute measurement is difficult 1 error
  _at_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
• Live time to be measured accurately by several
  methods

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Relative Normalization Analysis
e

• _at_Chooz 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)

n
?t
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How Good is Good Enough?
35
Understanding Mechanical Construction
Acrylic Target vessel (R1,2m, h2,8m, t 12mm)
Acrylic Gamma catcher vessel (R 1,8m, H 4
m, t 8mm)
LS 0,1Gd
LS
Stainless steel Buffer (R 2,75m, h 5,6m, t
4mm)
Muon VETO (shield) Thickness 150mm
36
Acrylic Integration

• Acrylic selected
• Material compatibility test ongoing
• (OK with Security Factor 8)
• Prototype 1/5 by june 2005
• (call for bid sent)

A special Tool will be developed to
rotate/insert the acrylic vessel into the pit
after PMT mounting
Test of accessibility in Chooz tunnel with
acrylic vessel model
CEA/DAPNIA
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Mechanical Studies
38
Scale (15) Prototype
PMT Cable Routing
Acrylic Target Vessel
LS 0,1Gd
LS
Acrylic Gamma Catcher Vessel
Stainless Steel Buffer
Muon VETO
Goal technical solutions for construction and
integration
39
Additional Work Ongoing

• 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 RD into the simulation effort
• Non-Proliferation
• Collaboration with LLNL and IAEA

40
Status of Double Chooz (Europe - I)

• 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

41
Status of Double Chooz(Europe - II)

• 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
• Rumors that the canceled BTeV may free up Italian
  money
• Russians have agreed to produce radioactive
  sources but little money is expected

42
Status of Double Chooz(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
• Establishing neutrino SAG
• Double Chooz Construction Proposal competes
  with RD requests from Braidwood and Daya Bay
• US groups are continuing to finalize design work
  on expectation of approval
• New groups are continuing to join
• Recent additions of Los Alamos and Livermore

43
Expected Schedule

• Detector Construction
• Can begin in 2006 (No known reason for delays in
  construction and installation of far detector)
• Near Laboratory
• Finalize designs in 2005
• Hope to have civil construction 2006-7
• Install near detector at end of 2007 or early
  2008
• Data Taking
• Can begin taking data with far detector as soon
  as it is installed (middle 2007)
• Near detector will hopefully follow in 16 months

44
Expected Sensitivity 2007-2012

• Far Detector starts in 2007
• Near detector follows 16 months later
• Double Chooz can surpass the original Chooz bound
  in 6 months

90 C.L. contour if sin2(2?13)0 ?m2atm 2.8
10-3 eV2 is supposed to be known at 20 by MINOS
45
Double Chooz Complements Off-Axis

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

from M. Shaevitz
Sensitivity regions for resolving the Mass
Hierarchy at 2? (with Proton Driver)
46
Conclusion outlook

• Strong Collaboration
• Saclay, APC, Subatech, TU Munich,
  MPIK-Heidelberg, Tubingen Univ., Univ. Hamburg,
  Kurchatov, Lousiana State, Drexel, Argonne, Univ.
  Alabama, Univ. Notre Dame, Kansas State, Univ.
  Tennessee, LNGS
• Experience from Chooz, Palo Verde, KamLAND,
  Borexino, LENS
• Known Technology
• Conservative design (incremental improvement on
  Chooz)
• Reasonably achievable improvements in detector
  systematics
• Known Environment
• Direct comparison to previous Chooz results /
  backgrounds
• Excellent Physics Opportunity
• Current Chooz bound is sin2(2?13)lt0.19 _at_ 90 C.L
• Expect sensitivity of sin2(2?13)lt0.02-0.03 with 3
  to 5 year run
• Continuing to maintain aggressive schedule
• Price is right!