Status of Double Chooz and first near detector data

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Status of Double Chooz and first near detector data Emmanuel Chauveau on behalf of the Double Chooz collaboration Research Center for Neutrino Science Tohoku University, Sendai, Japan GDR Neutrino, Marseille November 27th, 2014 1 / 21

Transcript of Status of Double Chooz and first near detector data

Page 1: 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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Page 2: Status of Double Chooz and first near detector data

Measurement of θ13 with reactor neutrinos

L/E (km/MeV)

-210 -110 1 10 2100

0.2

0.4

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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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Page 6: Status of Double Chooz and first near detector data

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

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trie

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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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IO

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1.01.2

Visible Energy (MeV)4 5 6 7 8 9 10

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trie

s

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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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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

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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

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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

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-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

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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

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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

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600

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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

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1.2

Visible Energy (MeV)1 2 3 4 5 6 7 8 9 10

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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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-0.1

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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

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2

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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

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Near detector integration (2/3)

Inner-Detector PMTs → acrylics vessels → chimney connections16 / 21

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Near detector integration (3/3)

detector closed → filling → top shielding → DAQ/electronics17 / 21

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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

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)

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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

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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

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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

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1000

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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

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ata/

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io

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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

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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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