Transcript Slide 1

Measurement of reactor antineutrino
disappearance driven by 13
New results
from all 3
this year
Steve Kettell
Brookhaven National Lab
NuFact 2013, IHEP, Beijing
1
Chooz, France
RENO, Korea
Daya Bay, China
Reactor
Neutrinos
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Neutrino Mixing
UMNSP Matrix
Maki, Nakagawa, Sakata, Pontecorvo
1
0

 0 cos 23

0 sin  23
U e1 U e 2 U e 3  0.8

 
U  U 1 U  2 U  3  0.4

 
U 1 U 2 U 3  0.4
  cos13
 
sin  23  
0


i CP
cos 23  
e sin 13
0
Super-K, MINOS,
T2K, NOvA
23 = ~ 45°
0.5
0.6
0.6
0 ei CP sin 13   cos12
 
1
0
 sin 12

0
cos13 
  0
Daya Bay, Double Chooz, RENO
MINOS,T2K, NOvA
13 = 9
U e 3 

0.7 
0.7 

sin 12
cos12
0
0 1
0
 
0 0 e i /
 
1 0
0
SNO, Super-K, KamLAND
12 ~ 34°
νe = cosθ13 (cosθ12 ν1 + sinθ12 ν2) +e-iδ sinθ13 ν3
νe  0.82 ν1 + 0.55 ν2 - 0.16 ν3
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Neutrino Mass
Δm2sol=m22-m127.5x10-5eV2
Δm2atm~=|m32-m12|2.4x10-3eV2
• Neutrinos have mass
•one small mass
difference (solar)
•one large mass
difference
(atmospheric)
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Neutrinos from Nuclear Reactors
•
•
•
Nuclear reactor fuel and subsequent fission fragments are neutron rich and decay by
turning neutrons to protons and emitting antineutrinos.
They produce a lot of antineutrinos: 61020 e/s/3GWth
We detect antineutrinos via the inverse beta decay (IBD) reaction
• Ee+ E - 0.8 MeV
Expected
Signal
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Measuring 13 with reactor neutrinos
m 2 L 
m 2 L 
4
2
2
Pee  1 sin 213 sin  31  cos 13 sin 212 sin  21 
 4 E 
 4 E 
2
2
•
•
•
•
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Measure relative rates in near and
far detectors to remove reactor
flux uncertainties
Build functionally identical
detectors to remove detector
mass and efficiency uncertainties
Measure distances accurately
Measure detector mass accurately
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Three active experiments
Experiment
Daya Bay
Double Chooz
RENO
Overburden Sensitivity
Power Detector(t)
(m.w.e.)
Goal (3-yr)
(GWth) Near/Far
Near/Far
(90%CL)
17.4
8.5
16.5
80/80
8/8
16/16
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250/860
120/300
120/450
~ 0.008
~ 0.03
~ 0.02
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Daya Bay
6 antineutrino detectors in 3 halls
 8 since Oct 2012
EH-2: Nov 5, 2011
320 t +
320 t
EH-3: Dec 24, 2011
6  2.9 GWth
EH-1: Sep 23, 2011
The RENO Experiment
16 ton,
120 m.w.e.
Near Detector
6  2.7
16.7 GWth
Far Detector
16 ton,
450 m.w.e.
Double Chooz
Mid-2014
Antineutrino Detectors
‘functionally identical’ detectors:
Reduce systematic uncertainties
Target mass measured to
3 kg (0.015%) during filling.
5m
All detectors filled from
common Gd-LS tanks.
LS
20t
Gd-LS
target
MO
192 8” PMTs: ~163 p.e./MeV.
Reflectors improve light collection and uniformity.
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Automated Calibration System
3 Automatic calibration units (ACUs) on each detector
R=1.7725 m
R=0
R=1.35m
Top view
3 sources in each ACU including:
• 10 Hz 68Ge (0 KE e+ = 20.511 MeV ’s)
• 0.5 Hz 241Am-13C neutron source (3.5 MeV n without )
+ 100 Hz 60Co gamma source (1.173+1.332 MeV )
• LED diffuser ball (500 Hz) for time calibration
Temporary special calibration sources:
Three axes: center, edge of target, : 137Cs (0.662 MeV), 54Mn (0.835 MeV), 40K (1.461 MeV)
middle of gamma catcher
n: 241Am-9Be, 239Pu-13C
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Muon Tagging System
Dual tagging systems: 2.5 meter thick two-zone water shield
and RPCs
• Outer layer of water veto
(sides and bottom) is 1m,
inner layer >1.5m. Water
extends 2.5m above ADs
•
•
288 8” PMTs per near hall
384 8” PMTs in Far Hall
• 4-layer RPC above pool
•
•
54 modules in near halls
81 modules in Far Hall
• Goal efficiency: > 99.5% with
uncertainty <0.25%
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Antineutrino
(IBD) event
selection
np→dγ
Fast neutrons
Signal
window
Prompt
Delayed
No additional prompt-like 400us before delayed and no delayed-like 200us after
“Identical” Antineutrino Detectors
Prompt Spectra
near
IBD
far
Expected ratio is 0.981
due to reactor core
distance.
Neutron Capture Time
Gadolinium concentration
is “identical” for the two
detectors
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RENO Status
 Data taking began on Aug. 1, 2011
with both near and far detectors.
(DAQ efficiency : ~95%)
 A (220 days) : First 13 result
[11 Aug, 2011~26 Mar, 2012]
PRL 108, 191802 (2012)
Near
A
 B (403 days) : Improved 13 result
[11 Aug, 2011~13 Oct, 2012]
NuTel 2013
 C (~700 days) : Shape+rate analysis
(in progress)
[11 Aug, 2011~31 Jul, 2013]
 Absolute reactor neutrino flux
measurement in progress
[reactor anomaly & sterile neutrinos]
Far
B
C
RENO Results
 RENO obtained the first result in April 2, 2012.
sin 2 213  0.113 0.013(stat)  0.019(syst )
 RENO has continued data-taking & data-analysis in a steady state, and
reported a new result in March, 2013.
sin 2 213  0.100 0.010(stat)  0.015(syst )
Far
observed
R  Far
 0.929 0.006(stat)  0.009(syst )
expected
 A clear deficit in rate
(7.1% reduction)
 Consistent with neutrino
oscillation in the spectral
distortion
Double Chooz
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Double Chooz
New rate analysis with
reactor rate modulation
sin2213 = 0.097  0.035
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Double Chooz
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Data Overview
A. Two AD Comparison:
arXiv:1202:6181
- Sep. 23, 2011 – Dec. 23, 2011 NIM A685:78
- Side-by-side comparison of 2 detectors
A
E
B. First Oscillation result: arXiv:1203:1669
- Dec. 24, 2011 – Feb. 17, 2012 (6 ADs)
- 1st observation of νe dis. PRL108:171803
B. Improved Result:
arXiv:1210:6327
- Dec. 24, 2011 – May 11, 2012
- 2.5x original data, CPC37:011001
B
D. New analysis
- Dec. 24, 2011 – July 28, 2012
- 4x original data; shape, m2ee analysis
E. Full experiment (8 AD)
C
- Oct. 19, 2012 – present
Results described in this talk
For details see Soeren Jetter in Friday 12:10 WG-1
Jiajie Ling talk at BNL
D
http://www.phy.bnl.gov/~partsem/fy13/BNL_Ling_dayabay.pdf
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Data Summary
EH-1
EH-2
EH-3
Over 300,000 antineutrino events
Consistent rates for side-by-side detectors
Uncertainty dominated by statistics
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Total backgrounds are 5%
(2%) in far (near) halls.
Backgrounds
Near Halls
σB/S
%
B/S
%
Far Hall
B/S
%
σB/S
%
Accidentals
1.5
0.01
4.0
0.04
Fast neutrons
0.1
0.07
0.06
0.03
9Li/8He
0.4
0.1
0.3
0.08
241Am-13C
0.04
0.02
0.36
0.16
13C(α,
0.01
0.01
0.05
0.03
n)16O
Estimate 9Li rate using
time-correlation with
muon
Background uncertainties are
0.3% (0.2%) in far (near) halls.
Simulated Am-C
source neutron
capture position
Constrain fast-n rate using
IBD-like signals in 10-50 MeV
Hot AmC source
deployment
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Uncertainty
Summary
Absolute Relative
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Influence of uncorrelated reactor systematics reduced by
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far vs. near measurement.
Antineutrino Rate vs. Time
Detected rate strongly
correlated with reactor
flux expectations.
Predicted Rate:
– Assume no oscillation
– Absolute normalization is
determined by data fit.
– Normalization is within a
few percent of
expectations.
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Shape and mass splitting
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Daya Bay
Status
 Near Site Operations (6/11-12/11)
 AD#1-2 comparison paper published
 NIM A685:78 (2012)
 First 13: March 8, 2012
Discovery of reactor e disappearance at ~2 km
 Phys.Rev.Lett. 108:171803 (2012)
 615 citations (~1.5 per day)
sin22θ13=0.092±0.016(stat)±0.005(syst)
 Updated result (55139 days) June 6, 2012
 Chinese Physics C37:011001 (2013)
sin22θ13=0.089±0.010(stat)±0.005(syst)
 6-AD (2-1-3) data (12/11-7/12)
sin22θ13=0.090+0.008-0.009
 Full 6-AD data analysis (217 days, shape & m232) |mee2 |=2.59+0.19-0.2010-3
 Final two ADs installed, calibration campaign completed 7-10/12
 Taking data with all 8-AD since Oct 19, 2012
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Future Plans
RENO’s Projected Sensitivity of 13
sin 213  0.100 0.010(stat.)  0.015(syst.)
2
(402 days) 0.100  0.018 (5.6 s)
(18 % precision)
2013. 3
 0.007 (~ 14 s)
(5 years)
(7 % precision)
 3 years of data : ±0.007 (7% precision)
- statistical error : ±0.010 → ±0.006
- systematic error : ±0.015 → ±0.005
ssyst =0.015
(7 % precision)
 Goals
- sin2213 to 7% precision
- direct measurement of m231
- precise measurement of reactor
neutrino flux and spectrum
- study for reactor anomaly and
sterile neutrinos
Double Chooz plans
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Daya Bay Plans
•
•
Measure of 13 with high precision
Measure mee2 complementary to
accelerator-based experiments.
•
Further scientific goals:
–
–
–
•
Measure reactor flux/spectrum: possibly resolve
ambiguities in reactor predictions and anomaly.
Multi-year measurement of reactor flux
throughout fuel cycles.
Measure neutron and spallation production for
various muon energies across DB depths.
Run for at least 3 years (thru 2015)
August 2012
8-AD run
Projected uncertainty in sin22θ13<4%. Reduction
Expect to achieve mee2 precision
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in uncertainty will improve CP reach of LBNE.
better than 110-4 eV2 after 3 years.
Accelerator experiments:
— normal, — inverted, CP=0, 23=45
Reactor experiments:
rate only, rate+shape, n-Gd, n-H
Summary
Daya Bay
sin22θ13=0.090+0.008-0.009
2|= (2.59
+0.19
-3
2
n-Heecoming
soon
|m
-0.20)10 eV
RENO
sin22θ13=0.100±0.010(stat)±0.015(sys)
Double Chooz
sin22θ13=0.109±0.030(stat)±0.025(sys) n-Gd
sin22θ13=0.097±0.034(stat)±0.034(sys) n-H
Electron neutrino contains 2 mass-splittings
(3 mass states) and the large splitting agrees
with that measured from muon neutrinos
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Backup
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Daya Bay
Selected as one of Science’s
top 10 breakthroughs of 2012.
“…result suggests that in the
coming decades neutrino
physics will be every bit as rich
as physicists had
hoped…neutrino physics could
be the future of particle
physics — as the fact that
neutrinos have mass is not
even part of the standard
model. If so, the Daya Bay
result may mark the moment
when the field took off.”
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Ling Ao 2
Ling Ao
Hall 3 (Dec 11)
Daya Bay
Experimental Halls
complete 12/24/11
Configuration
until July
2012
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Hall 1 (Aug 11)
Hall 2 (Nov 11)37
Definitive sin22θ13 measurement
– Important measurement of a fundamental parameter
• Daya Bay will have the best measurement for the foreseeable future
– Improve extraction of mass hierarchy and CP from accel. expts.
– Overconstrain PMNS matrix thru precision measurement of sin2213
– Improve ultimate precision on JCPν and allow tests of unitarity
Significance with which CP violation can be observed
by NOvA+T2K+LBNE, as a function of the true value
of CP. Observation of CP violation is equivalent to
the measurement CP0,. The significance is
calculated by minimizing over both the normal and
inverted hierarchies, as the mass hierarchy is not
assumed to be known. The effects of external
constraints on 13 from Daya Bay are shown.
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