Daya Bay and Other Reactor Neutrino Oscillation Experiments

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Daya Bay and Other Reactor Neutrino Oscillation
Experiments
Jen-Chieh Peng
University of Illinois at Urbana-Champaign
International Workshop on High Energy Physics in
the LHC Era Valparaiso, Chile, December 11-15,
2006
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Outline
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What we have learned from neutrino oscillation
experiments
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What we do not know about the neutrinos

• Dirac or Majorana neutrinos?
• Mass hierachy and values of the masses?
• Existence of sterile neutrinos?
• Value of the ?13 mixing angle?
• Values of CP-violation phases?
• Origins of the neutrino masses?
• Other unknown unknowns ..

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What we know and do not know about the neutrinos

• What is the ?e fraction of ?3? (proportional to
  sin2?13)
• Contributions from the CP-phase d to the flavor
  compositions of neutrino mass eigenstates depend
  on sin2?13)

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Why measuring ?13?
A recent tabulation of predictions of 63 neutrino
mass models on sin2?13
(hep-ph/0608137)

• Models based on the Grand Unified Theories in
  general give relatively large ?13
• Models based on leptonic symmetries predict small
  ?13

• A measurement of sin22?13 at the sensitivity
  level of 0.01 can rule out at least half of the
  models!

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Why measuring ?13?
A recent tabulation of predictions of 63 neutrino
mass models on sin2?13
(hep-ph/0608137)

• A measurement of sin22?13 AND the mass
  hierarchy can rule out even more models!

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Why measuring ?13?
Leptonic CP violation
If sin22?13gt0.02-0.03, then NOvAT2K will have
good coverage on CP d. Reactor experiments sets
the scale for future studies
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Current Knowledge of ?13
Global fit
Direct search
allowed region
Fogli etal., hep-ph/0506083
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Some Methods For Determining ?13
Method 1 Accelerator Experiments

• ?? ? ?e appearance experiment
• need other mixing parameters to extract ?13
• baseline O(100-1000 km), matter effects present
• expensive

Method 2 Reactor Experiments

• ??e ? X disappearance experiment
• baseline O(1 km), no matter effect, no ambiguity
  
• relatively cheap

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Discovery of the Neutrino 1956
F. Reines, Nobel Lecture, 1995
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Detecting?? Inverse ? Decay

• The reaction is the inverse ?-decay in 0.1
  Gd-doped liquid scintillator

0.3b
50,000b

• Time- and energy-tagged signal is a good
• tool to suppress background events.

• Energy of ??e is given by

E?? ? Te Tn (mn - mp) m e ? Te 1.8 MeV
10-40 keV
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Measuring ?13 with Reactor Neutrinos
Search for ?13 in new oscillation experiment
Small-amplitude oscillation due to ?13 integrated
over E
Large-amplitude oscillation due to ?12
1-1.8 km
detector 2
detector 1
gt 0.1 km
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Results from Chooz
Systematic uncertainties
Rate 5 evts/day/ton (full power)
including 0.2-0.4 bkg/day/ton
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How to Reach a Precision of 0.01 in sin22?13?

• Increase statistics
• Use more powerful nuclear reactors
• Utilize larger target mass, hence larger
  detectors
• Suppress background
• Go deeper underground to gain overburden for
  reducing cosmogenic background
• Reduce systematic uncertainties
• Reactor-related
• Optimize baseline for best sensitivity and
  smaller reactor-related errors
• Near and far detectors to minimize
  reactor-related errors
• Detector-related
• Use Identical pairs of detectors to do relative
  measurement
• Comprehensive program in calibration/monitoring
  of detectors
• Interchange near and far detectors (optional)

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World of Proposed Reactor Neutrino Experiments
Krasnoyasrk, Russia
Chooz, France
Braidwood, USA
Kashiwazaki, Japan
RENO, Korea
Diablo Canyon, USA
Daya Bay, China
Angra, Brazil
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Reactor ?13 Experiment at Krasnoyarsk, Russia
Original ideal, first proposed at Neutrino2000
Krasnoyarsk - underground reactor - detector
locations determined by infrastructure
Reactor
Ref Marteyamov et al, hep-ex/0211070
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KASKA at Kashiwazaki, Japan
- 7 nuclear power stations, Worlds most powerful
reactors - requires construction of underground
shaft for detectors
6 m shaft hole, 200-300 m depth
sin2(2?13) lt 0.02
http//kaska.hep.sc.niigata-u.ac.jp/
See poster by F. Suekane
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Daya Bay collaboration
Europe (3) (9) JINR, Dubna, Russia Kurchatov
Institute, Russia Charles University, Czech
Republic
North America (13)(46) BNL, Caltech, LBNL, Iowa
state Univ. Illinois Inst. Tech., Princeton, RPI,
UC-Berkeley, UCLA, Univ. of Houston, Univ. of
Wisconsin, Virginia Tech., Univ. of
Illinois-Urbana-Champaign,
Asia (13) (70) IHEP, CIAE,Tsinghua
Univ. Zhongshan Univ.,Nankai Univ. Beijing Normal
Univ., Nanjing Univ. Shenzhen Univ., Hong Kong
Univ. Chinese Hong Kong Univ. Taiwan Univ., Chiao
Tung Univ., National United Univ.
125 collaborators
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Location of Daya Bay

• 45 km from
• Shenzhen
• 55 km from
• Hong Kong

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The Daya Bay Nuclear Power Complex

• 12th most powerful in the world (11.6 GWth)
• Fifth most powerful by 2011 (17.4 GWth)
• Adjacent to mountain, easy to construct tunnels
  to reach underground labs with sufficient
  overburden to suppress cosmic rays

Ling Ao II NPP 2 ? 2.9 GWth Ready by 2010-2011
Ling Ao NPP 2 ? 2.9 GWth
1 GWth generates 2 1020 ??e per sec
Daya Bay NPP 2 ? 2.9 GWth
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Empty detectors moved to underground halls
through access tunnel. Filled detectors
transported between underground halls via
horizontal tunnels.
900 m
Ling Ao Near 500 m from Ling Ao Overburden 112
m
Ling Ao-ll NPP (under const.)
465 m
Construction tunnel
810 m
Ling Ao NPP
Filling hall
entrance
295 m
Daya Bay NPP
Total length 3100 m
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Conceptual design of the tunnel and the Site
investigation including bore holes completed
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Tunnel construction

• The tunnel length is about 3000m
• Local railway construction company has a lot of
  experience (similar cross section)
• Cost estimate by professionals, 3K /m
• Construction time is 15-24 months
• A similar tunnel on site as a reference

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Antineutrino Detectors

• Three-zone cylindrical detector design
• Target zone, gamma catcher zone
• (liquid scintillator), buffer zone (mineral
  oil)
• Gamma catcher detects gamma rays that leak out
• 0.1 Gd-loaded liquid scintillator as
• target material
• Short capture time and high released energy
• from capture, good for suppressing background
• Eight identical detector modules, each with 20
  ton
• target mass
• Identical modules help to reduce
  detector-related systematic uncertainties
• Modules can cross check the performance of each
  other when they are brought to the same location
  

20 ton 0.1 Gd-LS
? catcher
buffer
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Event Rates per Detector Module
Source Units DB LA far Use
Antineutrino Signal (day-1) 930 760 90 signal
Radioactive Backgrounds (Hz) 30 30 30 e-thresh.
Rock (Hz) 4 4 4
PMT glass (Hz) 8 8 8
other materials (steel) (Hz) 18 18 18
Gd contamination (Hz) 1 1 1
Muons (Hz) 24 14 1
Single neutron (day-1) 9000 6000 400 cal.
Tagged single neutron (day-1) 480 320 45 cal./bkg.
Tagged fast neutron (day-1) 20 13 2 Bkg est
b emitters (6-10 MeV) (day-1) 210 140 15 n-thresh.
12B (day-1) 400 270 28 cal.
8He9Li (day-1) 4 3 0 Bkg
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Key Requirements for Gd-LS for Daya Bay

• High light transmission high optical
  attenuation length (low optical absorbance).
• High light output in the Liquid Scintillator, LS.
• Long-term chemical stability, since the
  experiment will go on for at least 3 years.
• Stability of the LS means no development of
  color no colloids, particulates, cloudiness, nor
  precipitation no gel formation no changes in
  optical properties.

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BNL Gd-LS Optical Attenuation Stable So Far 700
days

• Gd-carboxylate in PC-based LS stable for 2
  years.
• - Attenuation Length gt15m (for abs lt 0.003).
• Promising data for Linear Alkyl Benzene, LAB
• (LAB use suggested by SNO experiment).

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Detector Prototype at IHEP

• 0.5 ton prototype
• (currently unloaded liquid scintillator)
• 45 8 EMI 9350 PMTs
• 14 effective photocathode coverage with
  top/bottom reflectors
• 240 photoelectron
• per MeV
• 9/?E(MeV)

prototype detector at IHEP
Energy Resolution
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Background Sources

• 1. Natural Radioactivity PMT glass, steel,
  rock, radon in the air, etc
• 2. Slow and fast neutrons produced in rock
  shield by cosmic muons
• 3. Muon-induced cosmogenic isotopes 8He/9Li
  which can ?-n decay
• - Cross section measured at CERN (Hagner et.
  al.)
• - Can be measured in-situ, even for near
  detectors with muon rate 10 Hz

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Cosmic-ray Muon

• Use a modified Geiser parametrization for
  cosmic-ray flux at surface
• Apply MUSIC and mountain profile to estimate
  muon intensity energy

DYB LingAo Mid Far
Overburden (m) 98 112 208 355
Muon intensity (Hz/m2) 1.16 0.73 0.17 0.041
Mean Energy (GeV) 55 60 97 138
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Muon Veto System
(Water buffer water cherenkov RPC tracker)

• Water shield also serves as a
• Cherenkov counter for tagging
• muons
• Water Cherenkov modules
• along the walls and floor
• Augmented with a muon
• tracker RPCs
• Combined efficiency of Cherenkov
• and tracker gt 99.5 with error
• measured to better than 0.25

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Summary of Systematic Uncertainties
sources Uncertainty
Reactors 0.087 (4 cores) 0.13 (6 cores)
Detector (per module) 0.38 (baseline) 0.18 (goal)
Backgrounds 0.32 (Daya Bay near) 0.22 (Ling Ao near) 0.22 (far)
Signal statistics 0.2
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Funding and other supports

• Funding Committed from
• Chinese Academy of Sciences,
• Ministry of Science and Technology
• Natural Science Foundation of China
• China Guangdong Nuclear Power Group
• Shenzhen municipal government
• Guangdong provincial government
• Gained strong support from
• China Guangdong Nuclear Power Group
• China atomic energy agency
• China nuclear safety agency
• Supported by BNL/LBNL seed funds
• Supported by DOE 800K RD fund
• Support by funding agencies from other
• countries regions
• China plans to provide civil construction and
  half of the detector
• systems U.S.plans to bear half of the
  detector cost

IHEP CGNPG
IHEP LBNL
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Schedule

• begin civil construction April
  2007
• Bring up the first pair of detectors Jun 2009
• Begin data taking with the Near-Mid
• configuration Sept 2009
• Begin data taking with the Near-Far
• configuration Jun 2010

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Sensitivity to Sin22q13

Other physics capabilities Supernova watch,
Sterile neutrinos,
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Double Chooz
10 tons detectors 8.4 GWth reactor power 300 mwe
overburden at far site 60 mwe overburden at near
site
1.05 km
Sensitivity sin2(2?13) lt 0.03 at 90 CL after 3
yrs, ?matm2 2 x 10-3 eV2
http//doublechooz.in2p3.fr/
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Reactor Experiment for Neutrino Oscillations
(RENO) at YongGwang, Korea
20tons (fid. vol.) of liquid scintillator
detectors 3 nearest detectors of 200300kg
scintillators Begin of data taking 2009/2010
sin2(2?13) lt 0.02
(88m high)
(260m high)
Near Detector
Tunnel length 100m
Far Detector
Tunnel length 600m
1.5 km
150m
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Prospects for a Reactor Measurement of sin22?13

• Angra, Brazil sin22?13 lt 0.005
• RD on reactor monitoring. Proposal for ?13
  measurement after Double Chooz.
• Daya Bay, China sin22?13 lt 0.01
• Approved by the Chinese Academy of Science for
  50M RMB.
• Other Chinese agencies are expected to
  contribute 100M RMB.
• US DOE has provided 0.8M for RD for FY06.
  Working towards US project start in FY08.
• Plan to start near-mid data taking in 2009, and
  begin full operation in 2010.
• Double-CHOOZ, France sin22?13 lt 0.03
• Funding committment in France and Germany.
• Begin running far detector in 2008.
• Complete near detector in 2009.
• RENO, Korea sin22?13 lt 0.02
• Approved by Ministry of Science and Technology
  for US 9M. RD program starting.
• Plan to begin data taking in 2009/2010.

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Neutrino Physics at Reactors
Past Experiments Hanford Savannah River ILL,
France Bugey, France Rovno, Russia Goesgen,
Switzerland Krasnoyark, Russia Palo Verde Chooz,
France Reactors in Japan
1956 First observation of neutrinos
1980s 1990s Reactor neutrino flux measurements
in U.S. and Europe
1995 Nobel Prize to Fred Reines at UC Irvine
2002 Discovery of reactor antineutrino
oscillation
2006 and beyondPrecision measurement of
?13 Exploring feasibility of CP violation studies
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S. Glashow