1
First Results from Double Chooz
• Current Status of Neutrino Oscillations and θ13 • Recent Double Chooz Results
On behalf of the Double Chooz Collaboration
MIAMI 2011 Conference
December 16th 2011
Brandon White, University of Tennessee
Double Chooz Collaboration
2 2
3
Oscillations • PMNS matrix describing the relationship between mass and flavor
eigenstates. • θ12, θ23, Δm2
21, and Δm231 oscillation parameters are now
experimentally known.
Atmospheric Super Kamiokanda & MINOS
Solar SNO & KamLand
€
s232 = sin2θ23 = 0.50−0.06
+0.07
Δm312 = 2.40−0.11
+0.12 ×10−3eV 2
€
s122 = sin2θ12 = 0.318−0.016
+0.019
Δm212 = 7.59−0.18
+0.23 ×10−5eV 2
€
U =
1 0 00 c23 s230 −s23 c23
⎡
⎣
⎢ ⎢ ⎢
⎤
⎦
⎥ ⎥ ⎥
c13 0 s13e−iδ
0 1 0−s13e
−iδ 0 c13
⎡
⎣
⎢ ⎢ ⎢
⎤
⎦
⎥ ⎥ ⎥
c12 s12 0−s12 c12 00 0 1
⎡
⎣
⎢ ⎢ ⎢
⎤
⎦
⎥ ⎥ ⎥
θ13 parameter is small making measurements difficult
4
Measuring θ13 • From reactor neutrino experiments looking for
survival of electron anti-neutrinos.
€
P νµ →νe( ) ≈ sin2θ23 sin2 2θ13sin2(Δ 31 −αL)(Δ 31 −αL)
2 Δ 312 + 2sin2θ13 sin2θ23 sin2θ12 cosθ13
sin(Δ 31 −αL)(Δ 31 −αL)
Δ 31
∗sin(αL)(αL)
Δ 21⋅ (cosΔ 32 cosδ − sinΔ 32 sinδ) + cos4 θ13 cos2θ23 sin
2 2θ12sin2(αL)(αL)2
Δ 212
• From accelerator neutrino experiments looking for appearance of electron neutrinos from muon neutrino beams.
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Reactor Neutrinos • Much cleaner measurement.
Eν = 4MeV Δm213 = 2.5 10-3 eV2
Short baseline reactor experiment sensitivity
Longer baseline reactor experiments KamLand sensitivity range Black sin2 2θ13= 0
Red sin2 2θ13= 0.1
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CHOOZ Experiment
• The original CHOOZ Experiment was designed to measure θ13. First results in 1998.
• Due to limited statistics and high systematic uncertainty of the absolute neutrino flux, only upper limits were set for sin2 2θ13 .
M. Apollonio[CHOOZ Collaboration], PLB 466 1999 415
sin2 2θ13 < 0.19 @ Δm213 = 2.0 10-3 eV2
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New Generation of Reactor Experiments
• Near and Far detectors are used in the new generation of detectors. • The relative rates between near and far will eliminate the reactor flux
uncertainty. Double Chooz: Far detector data taking since April 2011 First results presented at LowNu11 in November 2011 Near detector running early 2013
Reno: Both near and far detectors running since August 2011
Daya Bay: First Near Hall running since August 2011 Full running Summer 2012
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Accelerator Neutrino Experiments
• T2K: Running (delayed now due to the earthquake and tsunami) • MINOS: Running • Noνa: Under Construction
MIN
OS
: arX
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108.
0015
8
T2K
: arX
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106.
2822
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Double Chooz • Double Chooz was designed on improvements of
the first CHOOZ experiment. • Two identical detectors will be deployed, one at
the previous CHOOZ site (~1.05km from reactors) and a near detector (~400m from reactors).
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Detector Design
Target area: 10.3m3 liquid scintillator doped with Gd
Gamma Catcher: 22.3m3 liquid scintillator
Buffer Area: 110m3 non-scint. mineral oil
Inner Veto: 90m3 liquid scintillator
Outer Muon Veto:
Scintillator Plastic
15cm Steel Shielding
• Reactor electron anti-neutrinos are detected by inverse beta decay reactions inside the target area.
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Detecting Reactor Anti-Neutrinos • The electron anti-neutrinos are detected with inverse beta decay
reactions.
€
ν e + p = n + e+
€
Δt ≅ 30µs
Reactor Spectrum
Thermal Power from EDF Time Evolved Fission Rates
- Th.A. Mueller et al, Phys.Rev. C83(2011) 054615. - P. Huber, Phys.Rev. C84 (2011) 024617
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Calibration Data
68Ge In Gamma Catcher
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252Cf Source Spontaneous fission neutrons deployed in Target
Preliminary Data H Gd
Gd + H Gd + Gd
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Far Detector Outer Veto Outer Veto and Chimney
Muons tagged by OV and Inner Detector
Preliminary
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Inner Veto
Muon rates from Inner Veto Michel Electrons after tagged stopping Muons
Detector Timing working well down to the µs level
Preliminary
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Events Following Muons
H neutron Capture
Gd neutron Capture
Preliminary
Visible Energy Spectrum Rate of neutron capture on Hydrogen following Muons
Preliminary
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Backgrounds Accidental:
Gamma from radioactive contamination followed by a thermalized neutron from an untagged muon. Rate 0.332 0.004 day-1
Long lived Muon induced isotopes: Beta + n decay of 9Li and 8He Rate 2.3 1.2 day-1
Muon induced fast neutrons: Recoil proton followed by thermalized neutron. Rate 0.7 0.5 day-1
γ µ
n
µ
nβ
n
p +
+
+
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Two Reactors Off Data
• Double Chooz had the unique opportunity to have ~1 day of running with both reactors off.
Preliminary
• Two recorded events during this time within IBD prompt visible energy. • 9.8 MeV (200ms after high
energy Muon) • 4.8 MeV (241ms after high
energy Muon)
Consistent with background estimations from data
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Inverse Beta Decay • Neutrino event candidates via Inverse Beta Decay
Reactions: – Prompt Event (0.7-12 MeV visible energy) – Delay Event (6-12MeV visible energy) – Delta T between prompt and delay(2-100µs) – Veto events 1ms after tagged muons. – Multiplicity conditions
• No event 100µs before prompt events • Only delay event 400µs after prompt events
– Cut of PMT spontaneous light emission • Ratio of max charge/total charge • RMS of PMT hit time
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Timing and Spatial Distribution
• Time between Prompt and Delay events
• Distance between Prompt and Delay events
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Candidate Position Reconstruction
• No Cuts made on position
• Cuts are made for delay events to capture on Gd
• Well contained in target
Prompt Events
Delay Events
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Inverse Beta Decay Rates
Day0 20 40 60 80 100 120 140
)-1
Neu
trin
o R
ate
(day
0
20
40
60
80
rate�Expected
rate�Measured
Neutrino rate (background subtracted)
Double Chooz preliminary
Day0 20 40 60 80 100 120 140
Rat
e D
ata-
MC
rat
io
0.0
0.5
1.0
1.5
2.0
2.5
Neutrino Rate Data-MC ratio (background subtracted)
Double Chooz preliminary
24 Visible Energy Spectrums
Delayed energy [MeV]6 7 8 9 10 11 12
Eve
nts
/0.2
5 M
eV
0100200300400500600700800900
1000
Data
Neutrino MC
Double Chooz preliminary
Delayed energy [MeV]6 7 8 9 10 11 12
Eve
nts
/0.2
5 M
eV
0100200300400500600700800900
1000
Energy [MeV]2 4 6 8 10 12
Even
ts
0
100
200
300
400
500
600
700
PRELIMINARY
Double Chooz
DataNo Oscillation
) = 0.08513θ(22Best Fit: sin2 = 2.4e-3 eV13
2 mΔ @ Lithium-9Fast nAccidentals
Energy [MeV]2 4 6 8 10 12
Even
ts
0
100
200
300
400
500
600
700
Prompt Delay
Rate + Shape Analysis Rate Only Analysis
€
sin2 2θ13 = 0.085 ± 0.029(stat) ± 0.042(syst)
€
sin2 2θ13 = 0.093 ± 0.029(stat) ± 0.073(syst)
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Results Presented
First at LowNu11 Conference November 2011
More recently presented on CBS “The Big Bang Theory” December 2011
Episode: “The Speckerman Recurrence” Images Copyright CBS http://www.cbs.com/shows/big_bang_theory/video
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Combined Results
0
10
20
30
Δχ2
T2K+MINOS+CHOOZ+DCT2K+MINOS+CHOOZCHOOZDCDC+CHOOZ
★
0 0.1 0.2 0.3 0.4 0.5sin22θ13
-1
-0.5
0
0.5
1
δ / π
normal orderingΔm2
DC = 2.35e-3 eV2
68%, 95% CL (2 dof)
curves: T2K+MINOS +CHOOZshaded: T2K+MINOS +CHOOZ+DC
3σ
2σ
A non-zero θ13 value above 3σ.
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Comparison to Theory
0
2
4
6
8
10
12
14
16
18
20
Δχ2
arXiv:hep-ex/0410081v1
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Conclusion • Double Chooz Far Detector has been running stably
since April of this year, publication coming soon. • Double Chooz will continue to run with the Far detector
as the Near detector is built (completed 2013). • A “clean” measurement of a large θ13 will impact current
and future accelerator neutrino experiments probing for CP-violating phase and mass hierarchy.
€
P νµ →νe( ) ≈ sin2θ23 sin2 2θ13sin2(Δ 31 −αL)(Δ 31 −αL)
2 Δ 312
+2sin2θ13 sin2θ23 sin2θ12 cosθ13sin(Δ 31 −αL)(Δ 31 −αL)
Δ 31
∗sin(αL)(αL)
Δ 21⋅ (cosΔ 32 cosδ − sinΔ 32 sinδ)
+cos4 θ13 cos2θ23 sin
2 2θ12sin2(αL)(αL)2
Δ 212
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Thank You
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Backup Slides
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Readout Threshold
Preliminary
32
Data Analysed
33
Spontaneous Light Emission Cut
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Prompt vs Delay
prompt E (MeV)0 2 4 6 8 10 12
del
ayed
E (M
eV)
6
7
8
9
10
11
12
0
1
2
3
4
5
6
7delayed vs EpromptE
Double Chooz preliminary
35
Background There are unavoidable events that can mimic inverse beta decay
in our detector. Much care was taken in the detector construction to limit these
events. We must carefully determine the rate and energy spectrum of
these events to get a pure anti-neutrino spectrum.
€
ν e + p = n + e+
€
Δt ≅ 30µs
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Accidental Background
– Accidental background events come from prompt-like signal from radioactivity.
– Muon induced long lived isotopes resulting in beta + n.
– Fast Neutrons with recoil protons
γ
µ
n Gd
µ
9Li
n β
Gd n
p
Gd
37
Accidental BG • Accidental events are found by using an off time window between
prompt and delay events of Δt 1-100ms. • Rate 0.332 0.004 day-1
Preliminary
+
38
Correlated BG 9Li
• For 9Li events, look for time since last high energy muon to prompt event.
Rate 2.3 1.2 day-1
Preliminary
+
39
Correlated BG Fast Neutrons
• For Fast Neutron events, look at high energy prompt spectrum above neutrino signal energy range.
Rate 0.7 0.5 day-1 Preliminary
+
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Reactor Spectrum
• A total reactor errors of 1.74% remains for a far detector analysis only.
• Having two identical detectors will cancel these uncertainties.
Preliminary
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Preliminary Data • Stable Data taking at the Far Detector begain
April 13, 2011
Now over 100 days of physics data analyzed.
~75% physics data efficiency ~10% calibration data Preliminary
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Neutrino Future
€
P ν µ →ν e( ) ≠ P νµ →νe( )For accelerator experiments compare appearance rates for neutrinos and anti-neutrinos.
arX
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v2
Noνa: Beam from Fermi Lab to detector in Ash River MN Baseline 810km
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Two Reactors Off Data • Due to one reactor undergoing two month refueling period and
tests to the second reactor, one day of data was taken with both reactors off.
Preliminary
• Three recorded events during this time with prompt visible energy < 30MeV • 2 events with prompt
visible energy within the IBD spectrum range (9.8 and 4.8 MeV).
• 1 event with high prompt visible energy (26.5 MeV)
Consistent with background estimations from data
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Included Theories
arXiv:hep-ex/0410081v1
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Preliminary Results
Preliminary
Rate + Shape Analysis Rate Only Analysis
€
sin2 2θ13 = 0.085 ± 0.029(stat) ± 0.042(syst)
€
sin2 2θ13 = 0.093 ± 0.029(stat) ± 0.073(syst)
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