Post on 16-Oct-2021
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
1 / 21
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
2 / 21
Double Chooz experimental layout
3 / 21
Principle of ν̄e detection
4 / 21
2014 RESULTS WITHTHE FAR DETECTOR
(“DC-III” n-Gd)
5 / 21
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
0.2
0.4
0.6
0.8
1.0
1.2
Visible Energy (MeV)5 10 15 20
En
trie
s / M
eV
10
210
310
DC-III selection
DC-II selection
Double Chooz Preliminary
BG not subtracted
fast-n / stopping-μreduction
accidentalsreduction
DC
-III
/ D
C-I
IIR
AT
IO
0.0
0.2
0.40.6
0.8
1.01.2
Visible Energy (MeV)4 5 6 7 8 9 10
En
trie
s
1
10
210
310
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
10
210
310
Double Chooz Preliminary
BG not subtracted
accidentalsreduction
stopping-μreduction
DC-III selection
DC-II selection
— Prompt — — Delayed — — ∆T —
6 / 21
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
-610
-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
7 / 21
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
8 / 21
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
0
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
9 / 21
2014 Two reactors OFF results
Visible Energy (MeV)0 5 10 15 20
)-1
MeV
-1B
ack
grou
nd
Rat
e (d
ay
-0.2
-0.1
0
0.1
0.2
0.3
0.4
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
10 / 21
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
11 / 21
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
12 / 21
STATUS OF THE NEAR DETECTORFIRST COMMISSIONING DATA
13 / 21
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
14 / 21
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
18 / 21
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!)
19 / 21
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!)
19 / 21
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
0.04
0.05
0.06
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)
20 / 21
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
22 / 21
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
23 / 21
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
300
400
500
600
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
24 / 21
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
0.7
0.8
0.9
1
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
2000
3000
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)
25 / 21
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)
26 / 21
E/L structure vs other experiments
same pattern is confirmed by other reactor experiments
27 / 21
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!
28 / 21