Status of Double Chooz and first near detector data
Transcript of Status of Double Chooz and first near detector data
Status of Double Choozand first near detector data
Emmanuel Chauveauon behalf of the Double Chooz collaboration
Research Center for Neutrino ScienceTohoku University, Sendai, Japan
GDR Neutrino, MarseilleNovember 27th, 2014
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Measurement of θ13 with reactor neutrinos
L/E (km/MeV)
-210 -110 1 10 2100
0.2
0.4
0.6
0.8
1
NEA
R D
ETEC
TO
R
FAR
DETEC
TO
R
Sur
viva
l Pro
babi
lity
0
Pν̄e→ν̄e = 1 − sin2(2θ13) sin2(
∆m231L
4 E
)+ O(10−3) for L/E . 1
survival probability depends of L/Eν → measurement based on rate and shape deformation
reactor neutrinos: pure ν̄e , high intensity (∼ 1021 ν̄e/sec), low energy → short baseline,no oscillation parameters correlation and no matter effect (direct measurement)precise measurement of θ13 by 2 identical detectors (cancel flux & efficiency uncertainties)– far detector → disappearance of ν̄e around first minimum– near detector → unoscillated neutrino flux
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Double Chooz experimental layout
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Principle of ν̄e detection
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2014 RESULTS WITHTHE FAR DETECTOR
(“DC-III” n-Gd)
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DC-III new event selection
DC-II (2012) DC-III (2014)
Prompt Energy 0.7 – 12.2 MeV 0.5 – 20 MeV
Delayed Energy 6 – 12 MeV 4 – 10 MeV
∆ t 2 – 100 µs 0.5 – 150 µs
∆ R n/a < 1 m
isolation window [-100, +400] µs [-200, +600] µs
muon veto: ∆tlast−µ > 1 ms
OV veto: no OV hit coincident with prompt9Li veto: likelihood method trained with 12B9Li rejection > 50% with dead time < 0.5%
“FV” veto: point-like characterisation ofenergy deposit (reject stopping muons)
IV veto: reject fast-neutrons and accidentals
light noise: improved criteria on chargeisotropy and simultaneity of PMT signals
opened selection cut (more signal) + new vetos (less background)
DC
-III
/ D
C-I
IIR
AT
IO
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Visible Energy (MeV)5 10 15 20
En
trie
s / M
eV
10
210
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DC-III selection
DC-II selection
Double Chooz Preliminary
BG not subtracted
fast-n / stopping-μreduction
accidentalsreduction
DC
-III
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C-I
IIR
AT
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0.40.6
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1.01.2
Visible Energy (MeV)4 5 6 7 8 9 10
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trie
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10
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Double Chooz Preliminary
BG not subtracted
background reduction
DC-III selection
DC-II selection
DC
-III
/ D
C-I
IIR
AT
IO
0.20.40.60.81.01.21.4
Correlation Time (us)20 40 60 80 100 120 140
En
trie
s
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310
Double Chooz Preliminary
BG not subtracted
accidentalsreduction
stopping-μreduction
DC-III selection
DC-II selection
— Prompt — — Delayed — — ∆T —
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DC-III neutrino backgrounds
μn-Gd
β⁹Li
Visible Energy (MeV)2 4 6 8 10 12
Eve
nts
/ 0.5
MeV
0
20
40
60
80
100
120data
MC
DC-III (n-Gd) Preliminary
Cosmogenetic backgroundβ-n emitter (mainly 9Li)
0.97 +0.41−0.16 /day
DC-II: 1.25 ± 0.54 /day
μ
n-Gd
p-recoil
stopping-μ
Michel e¯
Visible Energy (MeV)2 4 6 8 10 12 14 16 18 20
Ent
ries
/ 0.
5 M
eV
210
310 IBD candidates
OV vetoed candidates
DC-III (n-Gd) Preliminary
Correlated backgroundfast neutrons, stopping-µ
0.60 ± 0.05 /dayDC-II: 0.67 ± 0.20 /day
μ
n-Gd
γ
Visible Energy (MeV)1 2 3 4 5 6 7 8 9 10
) / 2
50ke
V-1
Rat
e (d
ay
-710
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-510
-410
-310
-210
-110DC-III (n-Gd) Preliminary
Accidental backgroundnatural radioactivity
0.070 ± 0.005 /dayDC-II: 0.261 ± 0.002 /day
less background + more precise measurement of rate and shape
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DC-III neutrino candidates
Day0 100 200 300 400 500 600
)-1
Neu
trino
Rat
e (d
ay
0
20
40
60
80
100rateνExpected
Measured candidates rateDC-III (n-Gd) Preliminary
-10.3 day±Average Rate: 37.1-10.0 day±MC Average Rate: 37.5
PREVIOUS DATA SET NEW DATA
2 REACTORS ON
1 REACTOR ON
0 REACTOR ON
New Gd data set
data from April 2011 to January 2013live time: 467.9 days (previously: 227.9 days)→ including 7.5 days of two reactors OFF data17’358 neutrinos candidates (previously: 8’249 candidates)
statistics of neutrino candidates is doubled
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2014 Rate + Shape results (Gd)
0.25
MeV
Eve
nts
200
400
600
800
1000
1200
DC-III (n-Gd) PreliminaryLivetime: 467.90 days
Background-subtracted data
No oscillation
Systematic uncertainty
= 0.09013θ22Best fit: sin
2= 0.00244 eV2mΔat
0.25
MeV
Dat
a / P
redi
cted
0.8
0.9
1.0
1.1
1.2
Visible Energy (MeV)1 2 3 4 5 6 7 8 9 10
0.25
MeV
Dat
a - P
redi
cted
-100
-50
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50
JHEP 10 (2014) 086arXiv:1406.7763 [hep-ex]
sin2(2θ13) = 0.090 +0.035−0.028 previous results: 0.109 ± 0.039
excellent spectral distortion in 0.5 – 4 MeV (region constraining θ13 fit)origin of E/L structure > 4 MeV under investigation integrated effect negligible on θ13
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2014 Two reactors OFF results
Visible Energy (MeV)0 5 10 15 20
)-1
MeV
-1B
ack
grou
nd
Rat
e (d
ay
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BG model
2-Off BG
DC-III (n-Gd) Preliminary
only experiment with 7.5 days of data with all reactors OFF→ unique opportunity to measure backgroundobserved events rate: 0.97 ± 0.37 /day vs expected: 1.78 +0.43
−0.19 /day
good agreement in 4 – 8 MeV regionsmall deficit of data outside → disfavor missing/unknown background
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2014 Reactor Rate Modulation analysis
)-1Expected rate (day0 10 20 30 40 50
)-1
Ob
serv
ed r
ate
(day
0
10
20
30
40
50
Data
/dof=55/7)2χNo osc. (
/dof=4.5/5)2χBest fit (
90% CL interval
=1.02χΔerror defined as σ1
-1day-0.16
+0.18Background rate: 1.55
(stat+sys)-0.035+0.034) = 0.09013θ(22sin
DC-III (n-Gd) Preliminary
2 χΔ
0
5
10
)13θ(22sin
0 0.05 0.1 0.15 0.2
)-1
Bac
kgr
oun
d r
ate
(day
1
1.5
2
2.5
DC-III (n-Gd) Preliminary
99.7% C.L.
95.5% C.L.
68.3% C.L.
Best-fit
2χΔ0 5 10
exploit the 100 % variation in reactor power unique with Double Choozindependent measurement of θ13 (slope) and background (intercept):
sin2(2θ13) = 0.090 +0.034−0.035 background rate = 1.55 +0.18
−0.16 /dayconsistent with rate+shape fit and OFF-OFF datamost precise “rate-only” measurement
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More 2014 results ...
Precision Muon Reconstruction in Double ChoozNucl. Inst. Meth. A 764 (2014) 330 arXiv:1405.6227
Improved measurements of the neutrino mixing angle θ13 ...JHEP 10 (2014) 086 arXiv:1406.7763
Ortho-positronium observation in the Double Chooz ExperimentJHEP 10 (2014) 032 arXiv:1407.6913 −→ Timothée’s talk this afternoonfinalising an improved n-H analysis using DC-III data set
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STATUS OF THE NEAR DETECTORFIRST COMMISSIONING DATA
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Near Laboratory
Far Laboratory
Near Laboratory
larger laboratory divided into 3 clean roomsto parrallelise integration tasks for ≈ 1 year constructionlarger pit to afford a 1 m thickness water shielding around the detectordigging of tunnel + underground laboratory started in 2011laboratory fully delivered on May 2013 → beginning of the detector integration
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Near detector integration (1/3)
Inner-Veto vessel → Inner-Veto PMTs → Inner-Detector vessel15 / 21
Near detector integration (2/3)
Inner-Detector PMTs → acrylics vessels → chimney connections16 / 21
Near detector integration (3/3)
detector closed → filling → top shielding → DAQ/electronics17 / 21
Near detector commissioning status
detector is alive (ON) and stable for few weeks nowstart training shifters handling 2 detectors with new GUIsworking on data reduction scheme by DAQ: replace PMTs waveforms by reduced data(PMT charge, tstart, ..) for muon events tagged by trigger (> 200 Hz)
preparation of an automated data reconstruction at CC/IN2P3
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Observation of first “near” neutrinos
first neutrinos candidates were seen!basic selection based on DC-III cut: muon veto, ∆t prompt-delay, isolation window
clear and clean IBD signal (no calibration + no advanced reconstruction!)
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Observation of first “near” neutrinos
first neutrinos candidates were seen!basic selection based on DC-III cut: muon veto, ∆t prompt-delay, isolation window
clear and clean IBD signal (no calibration + no advanced reconstruction!)
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Future prospect with near+far detector
Total years of data-taking since April 20110 1 2 3 4 5 6 7 8
= 0.
113θ22
erro
r on
sin
σE
xpec
ted
1
0
0.01
0.02
0.03
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0.05
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0.07DC-II (n-Gd only): Far detector only
DC-II (n-Gd only): Near and far detectors
DC-III (n-Gd only): Far detector only
DC-III (n-Gd only): Near and far detectors
Range of potential n-Gd-based precision with near and far detectors
remarkable improvement with the new Gd analysisfirst data near the detector will improve sharply the precision(projection based on DC-III background model → improvement expected and in preparation)
expect to challenge a final sensitivity of ≈ 0.01 on sin2(2θ13)
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Talk summary
2014 results with far detector only:– more statistics, better selection and background rejection– sin2 2θ13 = 0.090 +0.035
−0.028 fully consistent with previous publications– new improved H analysis to follownear detector status:– detector is completed, filled and alive– excellent performance at early commissioning stagecoming phase with 2 detectors:– quick cancellation of systematics of flux and detection efficiency– target a final precision of ≈ 10 % on sin2(2θ13)– investigate further the E/L structure above 4 MeV– more physics: reactor anomaly, sterile neutrino, reactor monitor, ...
DOUBLE CHOOZ HAS TWO DETECTORS NOWSTAY TUNE FOR UPCOMING 2015 RESULTS!
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BACKUP
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E/L structure investigation: robustness of rate+shape fit
Visible Energy (MeV)1 2 3 4 5 6 7 8
0.25
MeV
Dat
a / P
redi
cted
0. 8
0. 9
1. 0
1. 1
1. 2 Background-subtracted data
No oscillationReactor flux uncertainty
Total systematic uncertainty
= 0.09013θ22Best fit: sin2= 0.00244 eV2mΔat
DC-III (n-Gd) PreliminaryLivetime: 467.90 days
test rate+shape fit with an additional/hypothetical background:n-C-capture-like peak (≈ 5 MeV) with several normalisations and shapes
largest deviation observed: 0.3 σ on sin2(2θ13), 0.1 σ on 9Li rate, < 0.1 σ on others
→ negligible impact on θ13
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E/L structure investigation: possible culprits
Visible Energy (MeV)4.0 4.5 5.0 5.5 6.0
Ent
ries/
40 k
eV
200
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DC-III (Gd-n) Preliminary
DATA
Visible Energy (MeV)4.0 4.5 5.0 5.5 6.0
Ent
ries/
40 k
eV
500
1000
1500
2000
2500MC
n-C peak reconstruction in GC
detection systematics: no impact on shapeenergy reconstruction: C-n peak in GC with ∆(data,MC) < 0.5 % → disfavoredbackground: constrained → possible but not only the sole causereactor flux: possible
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E/L structure investigation: correlation with reactor neutrino flux
Visible Energy (MeV)1 2 3 4 5 6 7 8
2On
-1O
n D
ata/
MC
Rat
io
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1.1
1.2Data
=0.0913θ22MC sin
Data
=0.0913θ22MC sin
Data
=0.0913θ22MC sin
Double Chooz preliminary
Visible Energy (MeV)3 4 5 6 7
Ent
ries
/ 0.2
5 M
eV
0
1000
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Gd-III
H-II
Double Chooz Preliminary
region of excess
extrapolation of IBD + its backgrounds
Number of Reactor(s) ONONE TWO ONE TWO
Exc
ess
rate
(/da
y)
0
1
2
excess after subtraction
all candidates scaled (same integral)
Gd-III H-II
“2-ON data” – “1-ON data” investigation of 4 – 6 MeV region (excess)
2 reactors ON data – 1 reactor ON data = pure 1-ON data (background free)→ deviation consistent with observation on rate+shape fit resultinvestigation of the region 4 – 6 MeV (excess of neutrino candidates):→ rate is correlated with flux of reactor neutrinos (empirical data-driven observation)
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E/L structure vs previous DC results
same pattern observed in DC-II resultswith different selection (Gd, H) and detector volume (H)better resolved with DC-III (more statistics, better energy scale and less background)
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E/L structure vs other experiments
same pattern is confirmed by other reactor experiments
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E/L distortion @Neutrino 2014
Reactor ν
Rate only analysis è Rate + shape analysis è
Semi -‐ What is this?!?
The field benefits greatly from 3 exps!
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