determining the neutrino mixing angle 13 with the daya bay nuclear power plants kam-biu luk...
TRANSCRIPT
Determining The Neutrino Mixing Angle 13 With The Daya Bay Nuclear Power
Plants
Kam-Biu Luk
University of California, Berkeley
andLawrence Berkeley National
Laboratory
Seminar at BNL, November 4, 2005
Kam-Biu Luk Daya Bay Experiment 2
Neutrino Mixing
Majorana phases
Six parameters: 2 m2, 3 angles, 1 phase + 2 Majorana phases
Pontecorvo-Maki-Nakagawa-Sakata Matrix
€
cosθ12 sinθ12 0
−sinθ12 cosθ12 0
0 0 1
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
cosθ13 0 sinθ13eiδ
0 1 0
−sinθ13eiδ 0 cosθ12
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
1 0 0
0 cosθ23 sinθ23
0 −sinθ23 cosθ23
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
1 0 0
0 e iδ1 0
0 0 e iδ 2
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
• For three generations of massive neutrino, the weak eigenstates are not the same as the mass eigenstates:
€
νe
νμ
ντ
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟=
Ue1 Ue2 Ue3
Uμ1 Uμ2 Uμ3
U τ1 U τ2 U τ3
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
ν1
ν2
ν3
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
solar ν reactor ν atmospheric ν neutrinolessreactor ν accelerator LBL ν accelerator LBL ν double- decay
• Parametrize the PMNS matrix as:
m12
m22
m32
m12
m22
m32
Normalhierarchy
Invertedhierarchy
m232
m221
Kam-Biu Luk Daya Bay Experiment 3
Neutrino Oscillation
• The probability of νμ νe appearance is given by:
• The probability of νe X disappearance is:
€
P νe → X( ) ≈sin2 213 sin2 m312 L
4E
⎛
⎝ ⎜ ⎜
⎞
⎠ ⎟ ⎟−cos4 13 sin2 212 sin2 m21
2 L
4E
⎛
⎝ ⎜ ⎜
⎞
⎠ ⎟ ⎟
€
P νμ → νe( ) ≈sin2 213 sin2 23 sin2 m312 L
4E
⎛
⎝ ⎜ ⎜
⎞
⎠ ⎟ ⎟
+ sin2 212 cos2 23 sin2 m212 L
4E
⎛
⎝ ⎜ ⎜
⎞
⎠ ⎟ ⎟
- (A ρ)cos2 13 sin13 sinδ
Kam-Biu Luk Daya Bay Experiment 4
Current Status of Mixing Parameters
(23, m232)
(12, m221)
(13, m231)
m231 m2
32 >> m221
12 and 23 are large
Unknowns: sin2213 , δ , sign of m2
32
m232 =(2.4+0.4
-0.3)10-3 eV2
23 45 m2
21 =(7.8+0.6-0.5)10-5 eV2
12 =(32+4-3)
Kam-Biu Luk Daya Bay Experiment 5
Current Knowledge of 13
Maltoni etal., New J. Phys. 6,122(04)
Sin2(213) < 0.09
Sin2(213) < 0.18
At m231 = 2.5103 eV2,
sin2213 < 0.15
Kam-Biu Luk Daya Bay Experiment 6
Some Ideas For Measuring 13
decay pipehorn absorbertargetp detector
+
+ μ+
Method 1: Accelerator Experiments
• appearance experiment:• need other mixing parameters to extract 13• baseline O(100-1000 km), matter effects present • expensive
Method 2: Reactor Experiments
• disappearance experiment: νe X• baseline O(1 km), no matter effects • relative cheap
QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.
€
ν μ → ν e
€
Pμe ≈sin2 213 sin2 223 sin2 m31
2L
4E ν
⎛
⎝
⎜ ⎜
⎞
⎠
⎟ ⎟+ ...
€
Pee ≈1−sin2 213 sin2 m31
2L
4E ν
⎛
⎝
⎜ ⎜
⎞
⎠
⎟ ⎟+ cos4 13 sin2 212 sin2 m21
2L
4E ν
⎛
⎝
⎜ ⎜
⎞
⎠
⎟ ⎟
Kam-Biu Luk Daya Bay Experiment 7
Synergy of Reactor and Accelerator Experiments
Δm2 = 2.5×10-3 eV2 sin2213 = 0.05
Reactor experiments can help in Resolving the 23 degeneracy
(Example: sin2223 = 0.95 ± 0.01)
90% CL
Reactor w 100t (3 yrs) + Nova Nova only (3yr + 3yr) Reactor w 10t (3yrs) + Nova
90% CL
McConnel & Shaevitz, hep-ex/0409028
90% CL
Reactor w 100t (3 yrs) +T2K T2K (5yr,ν-only) Reactor w 10t (3 yrs)+T2K
Reactor experiments providea better determination of 13
Kam-Biu Luk Daya Bay Experiment 8
Reactor νe
nXXnU 221
2 3 5
92+++
For 235U fission, for instance,
where X1 and X2 are stablenuclei e.g.
4094 Zr Ce140
58
yielding a total of 98protons, whereas 235U has 92protons. That is, on average, 6 neutrons must beta decay,giving 6 νes (per ~200 MeV).
νe/MeV/
fisson
3 GWth generates 6 × 1020 νe per sec
Kam-Biu Luk Daya Bay Experiment 9
Detection of ν in liquid scintillator:Inverse Decay
ν
μ
νe p e+ + n (prompt)
+ p D + (2.2 MeV) (delayed by ~180 μs)
+ Gd Gd* + ’s(sum = 8 MeV) (delayed by ~30 μs)
Time-, space- and energy-tagged signal is a goodtool to suppress background events.
Energy of νe is given by:
Eν Te+ + Tn + (mn - mp) + m e+ Te+ + 1.8 MeV 10-40 keV
Threshold of inverse decay is about 1.8 MeV; thus only about 25%of the reactor νe is usable.
Kam-Biu Luk Daya Bay Experiment 10
σ(E) =0.0952Eepe
1MeV2⎛ ⎝ ⎜ ⎞
⎠ ⎟ ×10−42cm2P(ν e → ν e)=1
- 42
Kam-Biu Luk Daya Bay Experiment 11
How To Measure 13 With Reactor νe?
0
2
4
6
8
10
0 2 4 6 8 10
Energy of ν ( )MeV
0.05 Number of Events per MeV
= 2 L km
sin2213 = 1
No oscillation
m231 = 0.0025 eV2
1. Rate deficit: deviation from 1/r2 expectation2. Spectral distortion
Kam-Biu Luk Daya Bay Experiment 12
Time Variation of Fuel Composition
Typically known to ~1%
235U
238U239Pu
241Punormalized flux times cross section (arbitrary units)
0 0.5 1 1.5 2 2.5 3 3.5
1 2 3 4 5 6 7 8 9 10E (MeV)
Kam-Biu Luk Daya Bay Experiment 13
Uncertainty in νe Energy Spectrum • Three ways to obtain the energy spectrum:
– Direct measurement– First principle calculation– Sum up anti-neutrino spectra from 235U,
239Pu, 241Pu and 238U 235U, 239Pu, 241Pu from their measured
spectra 238U(10%) from calculation (10%)
• Measurements agree with calculations to ~2%
Gö
sg
en
Bugey3 Measurement Best calculation
Bugey3 Measurementfirst-principle calculation
Kam-Biu Luk Daya Bay Experiment 14
Background
12B12N
Depends on theflux of cosmicmuons in thevicinity of thedetector
Go as deepas possible!
Keep everything as radioactively pure as possible!
KamLAND
Kam-Biu Luk Daya Bay Experiment 15
Location of Daya Bay
• 45 km from Shenzhen
• 55 km from Hong Kong
Kam-Biu Luk Daya Bay Experiment 16
LingAo II NPP:2 2.9 GWth
Ready by 2010
The Site
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
Daya Bay NPP:2 2.9 GWth
LingAo NPP:2 2.9 GWth
Kam-Biu Luk Daya Bay Experiment 17
Ranking of Nuclear Power Plants
0 2 4 6 8 10 12 14 16 18 20 22 24 26 GWth
1. Kashiwazaki (Japan) (7)
2. Zaporozhye (Ukraine) (6)
5. Gravelines (France) (6)
6. Paluel (France) (4)
6. Cattenom (France) (4)
9. Hamaoka (Japan) (5)
11. Fukushima Daini (Japan) (4)10. Ohi (Japan) (4)
8. Fukushima Daiichi (Japan) (6)
3. Yonggwang (S. Korea) (6)3. Ulchin (S. Korea) (6)
12. Daya Bay-Ling Ao (China) (4+2)~2010
Kam-Biu Luk Daya Bay Experiment 18
Horizontal Access Tunnels
• Advantages of horizontal access tunnel:
- mature and relatively inexpensive technology
- flexible in choosing overburden
- relatively easy and cheap to add expt. halls
- easy access to underground experimental facilities
- easy to move detectors between different
locations with good environmental control.
Kam-Biu Luk Daya Bay Experiment 19
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
A ~1.5 km-long Tunnel Onsite
Kam-Biu Luk Daya Bay Experiment 20
Cross Section of Tunnel For Daya Bay Experiment
1.2 m1.2 m7.2 m
0.8 m
3.2 m 3.2 m
Kam-Biu Luk Daya Bay Experiment 21
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
0.1 1 10 100
Nosc
/N
no_osc
Baseline (km)
Sin2(213) = 0.1m2
31 = 2.5 x 10-3 eV2
Sin2(212) = 0.825m2
21 = 8.2 x 10-5 eV2
Where To Place The Detectors ?
reactor near detector to measure raw flux at L1
far detector to measurechanges at L2
νe
Kam-Biu Luk Daya Bay Experiment 22
Where To Place The Detectors At Daya Bay?
Daya Bay
Ling Ao~1700 m
Kam-Biu Luk Daya Bay Experiment 23
Daya BayNPP
Ling AoNPP
Daya BayNear
Ling AoNear
Far site
Ling Ao-ll NPP(under const.)
590 m
1175 m 570 m
Possible Locations of Detector SitesEmpty detectors are moved to underground halls through an access tunnel with 8% slope.Filled detectors can be swapped between the underground halls via the 0%-slope tunnels.
Excessportal
Kam-Biu Luk Daya Bay Experiment 24
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
Location ofTunnel Entrance
Entrance portal
Kam-Biu Luk Daya Bay Experiment 25
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
Location of Daya Near Detector
Kam-Biu Luk Daya Bay Experiment 26
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
Location of Ling Ao Near Detector
Kam-Biu Luk Daya Bay Experiment 27
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
Location of Far Detector
Kam-Biu Luk Daya Bay Experiment 28
A Versatile Site• Rapid deployment:
- Daya near site + mid site - 0.7% reactor systematic error
• Full operation: (1) Two near sites + Far site (2) Mid site + Far site (3) Two near sites + Mid site + Far site Internal checks, each with different systematic
Kam-Biu Luk Daya Bay Experiment 29
What Target Mass Should Be?
Systematic error (per site): Black : 0.6% Red : 0.25% Blue : 0.12%
Solid lines : near+farDashed lines : mid+far
DYB: B/S = 0.5% LA: B/S = 0.4% Mid: B/S = 0.1% Far: B/S = 0.1%
m231 = 2 10-3 eV2
Kam-Biu Luk Daya Bay Experiment 30
Conceptual Design of Detector Modules
• Three-layer structure: I. Target: Gd-loaded liquid
scintillatorII. Gamma catcher: liquid
scintillator, 45cmIII. Buffer shielding: mineral oil,
~45cm • Possibly with diffuse reflection
at ends. For ~200 PMT’s around the
barrel:
vertex
14%~ , 14cm
(MeV)=
E Eσ σ
buffer
20t
Gd-doped
LS
gamma catcher
40 t
Kam-Biu Luk Daya Bay Experiment 31
~350 m
~97 m
~98 m~208 m
Cosmic-ray Muon• Apply the Geiser parametrization for cosmic-ray flux at surface• Use MUSIC and mountain profile to estimate muon flux & energy
DYB LingAo
Mid Far
Elevation (m) 97 98 208 347
Flux (Hz/m2) 1.2 0.94 0.17 0.045
Mean Energy (GeV)
55 55 97 136
near site
far site
Kam-Biu Luk Daya Bay Experiment 32
Conceptual Design of Shield-Muon Veto
• Detector modules enclosed by 2m+ of water to shield neutrons and gamma-rays from surrounding rock• Water shield also serves as a Cherenkov veto• Augmented with a muon tracker: scintillator strips or RPCs• Combined efficiency of Cherenkov and tracker > 99.5%
detectormodule
PMTsTracker
rock
Kam-Biu Luk Daya Bay Experiment 33
Alternative Design
40t-3 layermodule
top ofwater pool
Kam-Biu Luk Daya Bay Experiment 34
Background Inside Detector
Two classes of background:
1. Uncorrelated:
Accidental ─ random coincidence of two unrelated events appear close in space and time.
2. Correlated::
Fast neutron ─ a fast spallation neutron gets into the detector, creates a prompt signal (knock-out proton), thermalizes and is captured.
CosmogenicCosmogenic isotopes isotopes ─ 9Li and 8He with β-n decay modes are created in spallation of μ with 12C. Thedecays mimic the antineutrino signal.
Kam-Biu Luk Daya Bay Experiment 35
-n Decay Of 8He And 9Li
Correlated final state: Correlated final state: ββ+n+2+n+2αα
Correlated final state: Correlated final state: ββ+n++n+77LiLi
τ½ = 178 ms 49.5% Correlated
τ½ = 119 ms 16%
Correlated
Kam-Biu Luk Daya Bay Experiment 36
Background
Near Site
Far Site
Radioactivity (Hz) <50 <50Accidental B/S <0.05% <0.05%
Fast Neutron background B/S
0.15% 0.1%
8He/9Li B/S 0.55% 0.25%
• Use a modified Palo-Verde-Geant3-based MC to model response of detector.
• Cosmogenic isotopes: 8He/9Li which can -n decay - Cross section measured at CERN (Hagner et. al.)
- Can be measured in-situ, even for near detector with muon rate ~ 10 Hz.
The above number is before shower-muon cutwhich can further reduce cosmogenic background.
20t moduleQuickTime™ and a
TIFF (LZW) decompressorare needed to see this picture.
Kam-Biu Luk Daya Bay Experiment 37
Detector Systematic Issues
Potential sources of systematic uncertainty are:
• detector efficiency • gadolinium fraction (neutron detection efficiency)• target mass• target chemistry: fraction of free proton (target particle) in terms of hydrogen/carbon• trigger efficiency• cut efficiency• live time• surprises at the 0.01 level
Kam-Biu Luk Daya Bay Experiment 38
Possible Solutions
• Relative detector efficiency Calibrate all detectors with the same set of radioactive sources.
• Gd fraction (i) Control synthesis of liquid scintillator (ii) Measure the Gd- to H-capture ratio
• Target mass(i) Use the same batch or equally splitting batches of liquid scintillator, and measure flow rates(ii) Use νe events to cross calibrate, implying moving detectors.
Kam-Biu Luk Daya Bay Experiment 39
Detector Systematic Uncertainties
permodule
absolute measurementsrelative
measurement
0.10.1
0.1
0.25%
Kam-Biu Luk Daya Bay Experiment 40
• Topography survey: Completed• Geological Survey: Completed
• Verified topographic information• Generated new map covering 7.5 km2
• Geological Physical Survey: Completed• High-resolution electric resistance• Seismic • Micro-gravity
• Bore-Hole Drilling: November-December, 2005
Geotechnical Survey
raw data
Kam-Biu Luk Daya Bay Experiment 41
Daya BayNPP
Ling AoNPP
Daya Bay Near360 m from Daya BayOverburden: 97 m
Far site1600 m from Lingao1900 m from DayaOverburden: 350 m
Ling Ao-ll NPP(under const.)
8% slope
672 m(12% slope)
Ling Ao Near500 m from LingaoOverburden: 98 m
Mid site~1000 m from DayaOverburden: 208 m
Total length: ~3200 m
Kam-Biu Luk Daya Bay Experiment 42
• Daya Bay site Daya Bay site - baseline = 360 m- baseline = 360 m
- target mass = 40 ton- target mass = 40 ton
- B/S = ~0.5%- B/S = ~0.5%
• LingAo site LingAo site - baseline = 500 m- baseline = 500 m
- target mass = 40 ton- target mass = 40 ton
- B/S = ~0.5%- B/S = ~0.5%
• Far site Far site - baseline = 1900 m to DYB - baseline = 1900 m to DYB
corescores
1600 m 1600 m to LA coresto LA cores
- target mass = 80 ton- target mass = 80 ton
- B/S = ~0.2%- B/S = ~0.2%
• Three-year run (0.2% Three-year run (0.2% statistical error)statistical error)
• Detector residual error = Detector residual error = 0.2%0.2%
• Use rate and spectral Use rate and spectral shapeshape
90% confidence level90% confidence level
Sensitivity of sin2213
Sept, 2005
2 near + far
near (40t) + mid (40 t)
1 year
Kam-Biu Luk Daya Bay Experiment 43
Precision of m231
sin2213 = 0.02
sin2213 = 0.1
Kam-Biu Luk Daya Bay Experiment 44
Gd-loaded Liquid Scintillator
• It can significantly reduce backgrounds
(short capture time, high capture energy)
• Problems:
(a) doping Gd into organic LS from inorganic
Gd compound and achieve Light yield = 55% of
anthracene Att. length = 11m
(b) Aging Palo Verde: 0.03%/day Chooz: 0.4%/day
Kam-Biu Luk Daya Bay Experiment 45
Synthesis of Gd-loaded Liquid Scintillator• Investigating a few candidates at IHEP:
Date 2005.
06.13
2005.
08.01
2005.
08.26
Gd (%) 0.1 0.098 0.1
One candidate:
- 0.1% Gd (D2EHP-ligand) in
20% mesitylene-80% dodecane
- Light yield: 91% of pure LS
- attenuation length = 6.2 m
- stable for more than two months:
- no effect on acrylic
• R&D collaborative effort at BNL: - Gd (carboxylate ligands) in PC and dodecane - all stable for almost a year
Kam-Biu Luk Daya Bay Experiment 46
Prototype Detector at IHEP• Constructing a 2-layer prototype with
0.5 t Gd-doped LS enclosed in 5 t of
mineral oil, and 45 8” PMTs to evaluate
design issues at IHEP, Beijing
Steel tank
acrylic vessel
PMT mount
Front-end board (version 2)
Kam-Biu Luk Daya Bay Experiment 47
Installing proptubes in Sept, 2005
The Aberdeen Tunnel Experiment• Study cosmic muons & cosmogenic background in Aberdeen Tunnel, Hong Kong.
similar geologybetween Aberdeen and Daya Bay
Overburden ~Daya Bay sites
Kam-Biu Luk Daya Bay Experiment 48
Precision Measurement of 12 and m221
Kam-Biu Luk Daya Bay Experiment 49
Precise Measurement of 12
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
0.1 1 10 100
Nosc
/N
no_osc
Baseline (km)
Large-amplitude oscillation at ~55 km
due to 12
• Near detectors close to reactors measure raw flux and spectrum of νe, reducing reactor-related systematic
• Position a far detector near the first oscillation maximum to get the highest sensitivity of 12
Sin2(213) = 0.1m2
31 = 2.5 x 10-3 eV2
Sin2(212) = 0.825m2
21 = 8.2 x 10-5 eV2
• Since reactor νe are low-energy, it is a disappearance experiment:
KamLAND
Kam-Biu Luk Daya Bay Experiment 50
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.Tai Mo Shan(957 m)
~55 km
Daya BayNPP
Hong Kong
Shenzhen
Location of Hong Kong Site For 12 Measurement
Kam-Biu Luk Daya Bay Experiment 51
Precision of 12 With The Daya Bay Facility
Inputs:• Thermal power = 17.4 GW• Baseline = 55 km• Target mass = ~ 500 ton LS• Mixing parameters:
sin2212 = 0.825
sin2213 = 0.1
m212 = 8.2 10-5 eV2
m213 = 2.5 10-3 eV2
Kam-Biu Luk Daya Bay Experiment 52
Summary and Prospects• The Daya Bay nuclear power facility in China and the mountainous
topology in the vicinity offer an excellent opportunity for carrying out a reactor neutrino program using horizontal tunnels.
• The Daya Bay experiment has excellent potential to reach a sensitivity of 0.01 for sin2213.
• The three Chinese funding agencies are discussing cost-sharing of a request of RMB$200 million.
• The US team is waiting for the NuSAG’s decision.
• Will complete detailed design of detectors, tunnels and underground facilities in 2006.
• Plan to commission the Fast Deployment scheme in 2007-2008, and Full Operation in 2009.
• Welcome more collaborators to join.
Kam-Biu Luk Daya Bay Experiment 53
What Have We Learned From Chooz?
CHOOZ Systematic Uncertainties
Reactor ν flux & spectrumDetector Acceptance
2%1.5%
Total 2.7%
5 t Gd-loaded liquid scintillatorto detect
L = 1.05 km
D = 300 mwe
P = 8.4 GWthRate: ~5 evts/day/t (full power) including 0.2-0.4 bkg/day/t
νe + p e+ + n
e+ + e- 2 x 0.511 MeV n + Gd 8 MeV of s; τ ~ 30 μs
~3000 νe candidates(included 10% bkg) in335 days