Double Chooz 1st Results
and Related Topics

Fumihiko Suekane
RCNS, Tohoku Univ.

2012.3.29 @ICRR
25th 宇宙ニュートリノ研究会
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I made the following talk on Nov./2002 here.	

It was my 1st workshop talk on this subject.	

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And we published this paper on 2003.	

This is the 1st paper pointing out reactor-accelerator complementarity.	

(Cited 166 times (Spires)) 	

9 years have passed 	
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Then we formed KASKA project which uses Kashiwazaki-Kariwa
Nuclear Power Station in 2002 and performed R&D and wrote LoI.
However, it was not funded and we joined Double Chooz in 2007.	
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Contents* Motivation* Reactor Neutrino Experiment* Double Chooz Experiment* Results* Relation with Other Results* Future possibilities of reactor
experiments* Summary
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Why we study neutrino oscillation
There are many oscillations (Irrespective to it is observable or not)	
00
00＊ K ⇔ K , B ⇔ B Oscillation． CP violation＊spin precession by B (= ⇑ ⇔ ⇓ oscillation)  Formation of Q.M.
€€€

＊21cm wave of Hp(⇑)e(⇓) ⇔ p(⇓)e(⇑) oscillation

 Astronomy＊ uu ⇔ dd oscillation in π0  Hadron structure, mass pattern. QCD€＊ d ⇔ s oscillation Cabbibo angle, Higgs-Quark coupling€* B ⇔ W3 oscillation  EW theory, Weinberg angle, Higgs-GB coupling.

 These oscillations are related to important physics.

€ Neutrino Oscillation ν α ⇔ ν βshould be related toimportant physics, too.
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Purpose of ν oscillation experiments	is to measure ν flavor transition amplitudes
and to give hints to theorists to explain our world
and to construct unified theory.
Now we know

να

νβ

H0

H0

Non Standard Higgs?

exists.
or

Sub Structure??
dG

For Example, d?

PS mixing	ss⎛π 0 ⎞ ⎛ 0.7 0.7
0 ⎞⎛ uu ⎞⎜ ⎟ ⎜
⎟
⎟⎜
η
~
−0.4
0.4
0.8
dd
⎜ ⎟ ⎜⎟⎟⎜⎜ ηʹ′ ⎟ ⎜ 0.6 −0.6 0.6 ⎟⎜ ss ⎟⎠⎝⎠⎝ ⎠ ⎝Or something else??

?
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CKM matrix & MNS matrix	
CKM mixing matrix	⎛d ʹ′⎞ ⎛ 0.9743 0.2253 0.0035 ⎞⎛d ⎞⎟⎜ ⎟⎜ ⎟ ⎜ʹ′s=0.2252
0.97350.041⎟⎟⎜⎜ s ⎟⎟⎜⎜ ⎟⎟ ⎜⎜⎝ bʹ′⎠ ⎝0.0086 0.040 0.9992 ⎠⎝ b ⎠Neutrino mixing matrix (MNS matrix) before 2011	€⎛ ν e ⎞ ⎛ 0.8 0.5 sin θ13eiδ ⎞⎛ν1 ⎞⎟⎜ ⎟⎜ ⎟ ⎜sinθ13<0.2	

ν
~
0.4
0.6
0.7
ν
⎟⎜ 2 ⎟⎜⎜ µ ⎟⎟ ⎜
⎜0.4 0.6⎟⎜ν ⎟
ν0.7
⎝ τ ⎠ ⎝⎠⎝ 3 ⎠* Finite size of θ13 was not known* CP violation depends much on θ13 (as well as on other angles) Need€ to measure120329suekane@ICRR

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Importance of determinatin of θ13* It is one of the fundamental parameters.
* Future ν experiments strongly depends on θ13.
Parameter	δCP	θ23 degeneracy	

Measurement Method 	[P (ν µ → ν ) − P (ν µ → ν )]
A

e

A

e

@Δ 23

~ 0.1sin 2θ13 sin δ

2
2
P
ν
→
ν
+
P
ν
→
ν
~
2
sin
θ
sin
2θ13
[ A ( µ e ) A ( µ e )]@Δ
23
23

Mass Hierarchy

€

2
2
ʹ′
ʹ′
P
ν
→
ν
;
L
+
P
ν
→
ν
;
L
~
sign
Δm
L
−
L
sin
2θ13
(
)
[ A ( €µ e ) A ( µ e )]@Δ 23( 23 )
PR (ν e → ν e )@Δ12 ~ 1− 0.5 sin 2 2θ13 (sin 2 Δ 31 + tan 2 θ12 sin 2 Δ 32 )€€We can not go further without knowing θ13.	
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9€How θ13	 can be measured	 Δm132 L π@~
4E
2

E~MeV, L~1km
Reactor Experiments
E~GeV, L=100~1000km; Accelerator experiments
ντνµ2
E Δm13~L
2π

2
P (ν µ → ν e ) = sin€
θ 23sin 2 2θ13

€ δ
− 0.045 ⋅ sin2θ13sin€

P (ν µ → ν τ ) = cos2θ 23sin 2 2θ13
+ 0.045 ⋅ sin2θ13sinδνeAccelerator
Measurements
P (ν e€→€ν µ ) + P (ν e → ν ) = sin 2 2θ13
T2K, MINOS, NOvA
Reactor measurements
τDoubleChooz, Dayabay, RENO
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Why reactor measurement is important	  θ23 degeneracy

0.50 ± 0.11
2
PAC (ν µ → ν e ) =sin
2θ13 ± 0.045sin2θ13sinδ
2(1  0.00017L [km])δ dependece

Mass Hierarchy€
Hypothetical example	  120329suekane@ICRR

Contrary, reactor 	measurement is pure 	

sin22θ13 measurement 	&	
Combining Reactor and 	

Accelerator will restrict 	parameter space. 	

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Reactor neutrino & Its detection
235nν e + p → e+ + nU

γ(0.511MeV)

e-

236

*

U

€

γ(0.511MeV)e+νeprompt signalpnDelayed signal

n
e

ν

94

140

Te

e-

Rb
e

140

I

94

30μs

γ

n

γ
Gd

νe
-

∑ E ~ 8MeV
γ

γ

Sr

γ

νe

νe

e-

140

Xe
νe

e-

94

e-

Y

νe
140

Cs

94

σ (ν e + p → e+ + n)

Zr e

ν are produced in
β-decays of fission products.	

~ 6 ×10 20 ν e / s / reactor
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How to measure θ13 by reactor neutrinos	ν e Detector
ν e + p → e+ + n
sensitive only to ν	

 eReactor= Rich ν e Generator	ν oscillation	
€ νµ
€
νe

νe
νe

€

1.5x1021ν/s 	

 €@Chooz reacors	

deficit of ν e 	

€

€

€

€

Signal	€~1km	
Deficit of ν e ∝ sin22θ13 	

sin2(2θ13)=0.04
sin2(2θ13)=0.1
sin2(2θ13)=0.2

P(ν e → ν e ) = 1− sin 2 2θ13€
The probability for ν e to remain ν e	ν e spectrum€

120329€€E (MeV)	
 13

suekane@ICRR€

How to realize good precision: 2 detector scheme	

sin22θ13=0.1	

Eν=4MeV	

Original idea Kr2Det	

sin22θ12	

P (ν e → ν e )sin22θ13	

Far
Near
Detector	
 Detector	

€Ratio measurement Far/Near Detectors => Cancels most systematics	

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Then we are performing Double Chooz
experiment to measure Pure θ13	νe	Chooz Reactors
4.27GWth x 2 cores	
120329Near Detector<L> 400m
400ν/day
120m.w.e.
suekane@ICRR

Far Detector<L> 1050m
70ν/day
300m.w.e.
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Double Chooz collaboration	

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DoubleChooz Collaborationmeeting @ Tohoku 2012	

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DC-Japan 	*Tohoku Univ.,*Tokyo Institute of Technology,*Tokyo Metropolitan Univ.,*Niigata U., Kobe Univ.,*Tohoku Gakuin Univ.,*Hiroshima Institute of Technology
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Main Components 	

of DC Detector	

Target ν :10m3 Gd loaded Liquid Scintllator
8mmt Acrylic Tankγ Catcher :Liquid Scintillator
12mmt Acrylic Tank

22m3

Light Detection:
390 Low BKG 10’’ PMTs

7m	

Buffer oil :110m3 Paraffine Oil
3mmt Stainless Steel Tank
Inner Muon Veto :90m3 LS + 78 8’’ PMTs
Iron shield:
15cmt
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7m	

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DC Milestones	
(2008/5~) 2010/10	

2010/12/	

2011/4	

2011/7	

2011/11	

2013	

120329Far Detector Structure complete	

Liquid Scintillator Loading 	Far detector commissioning	Physics data taking started.	

Excavation of near tunnel started	Outer Veto Detector in Operation	

1st Result @ LowNu conference	

(Accepted by PRL)	

Near Detector will be in Operation	

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23/12/2010: Official start of Double Chooz	
Press release 23/12/2010	

Tohoku Univ. News	Pysics Run Start 2011/4/13	

Data taking time and efficiency	

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Stability of Liquid scintillator	
  

±1%	

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Trigger Efficiency 	

Analysis
Threshold	Physics Thresholde+e-  2γ (1.02MeV)	

100+0-0.4% @0.7MeV	

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Calibration Systems
Glove Box

Fish-line

GC guide Tube

Embedded LED
calibration system
385, 420, 470 nm

120329Buffer guideTubesuekane@ICRR
F. Ardellier, Ch. Veyssière, Th. Lasserre, D. Lhuillier, CEA-Saclay, Nov. 09th 201126

Energy calibration	
e.g.) 68Ge positron source（e+e- annihilation1.02 MeV γs）	@ Detector Center	
Guide-tube systemin γ-catcher	Double Chooz preliminary	

1203292011/11/17	

suekane@ICRR

Double Chooz preliminary	2727	

Neutrino Signal	
γ(0.511MeV)e-γ(0.511MeV)e+νeprompt signalpnDelayed signal

Ed	

30μs

γ

γ
Gd

∑ E ~ 8MeV
γ

γ

γ

Ep	

Prompt signal	
Delayed signal	
t	

τ~30µs	

120329

1~8MeV	suekane@ICRR

8MeV	

28

12MeV for rate analysis	

0.7MeV	

Ep cut (ε=99.9±0.1%)	

Physics thresholde+e-  2γ (1.02MeV)	
120329(Actual data will be shown at result page.)	
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TDelay - TPrompt cut	

Edelay cut	ε=94.5±0.6%	

ε=96.5±0.5%	

Difference (~1%) is taken into 	

account in the error. 	

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Event Selection Summary	
Condition	

Trigger efficiency	

0.7MeV < E 	

Efficiency [Inefficiency]	

100+0-0.4% [0+0.4-0.0%] 	

0.7MeV < Ep < 12MeV	

 99.9±0.1% [0.1±0.1%] 	

Neutrino Selection	

After Muon Cut	6MeV < Ed < 12MeV 	

 94.5±0.6% [14.0±0.6%]	

2µs < ΔTp-d < 100µs	

96.5±0.5% [3.5±0.5%]	

1ms < ΔTm-p 	

95.5±0.0% [4.5±0.0%] 	

Multi Neutron
rejection	

<3 triggers	

99.5±0.0% [0.5±0.0%]	

@-100µs< ΔTp<400µs	

Light noise rejection	

MaxQ/TotalQ	

signal time structure 	

100±0.0% [0.0±0.0%]	

Gd Capture efficiency	

86.0±0.5% [14.0±0.5%]	

Total	

74±1.0%	

1203294121 events Remained	
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120329

1 Reactor 0FF	suekane@ICRR

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Back grounds	

Accidental BG	* e+-like signal: γ-rays from radioactivity	

(208Tl, etc.). 	

n-signal: n from muon induced spallation 	

ΔT accidentally <100us	

Correlated BG	

* Long Life (9Li, 8He) 	

β+n –decaying spallation isotopes	

* Fast neutrons: 	

Recoil proton + neutron capture	* Stopping muon + its decay 	

(Michel electron)	

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Stability of accidental BKG	120329suekane@ICRR

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120329

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120329

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Reactor Off-Off	
OFF	
OFF	

OFF-OFF data	• Reactor 1 stopped for 2 months (refueling)• Reactor 2 stopped for 1 day (maintenance) In-situ background measurement (Unique capability of Double Chooz)	
2 events within 0.7~12 MeV… (Agree with the estimation)	
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120329

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Background summary	Background

Rate/day	error(%)	

Accidental	

0.33	

<0.1	

Fast Neutron	

0.83	

0.9	

9Li	

2.3	

2.8	

Total

3.46
(335events)	

3.0

Observed Neutrino =4121-355=3766 events	

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Expected Neutrino Flux	
Bugey4 (L~15m) is considered as "near detector".
(Water target & 3He proportional counter. only neutron
was tagged (=no prompt energy threshold))	

Bugey4; Uncorrelated error with DC (1.7%)
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Expected Neutrino Event rate Calculation	

N p ε Pth (t)(E,t) =
×
× σf
2
4π L
Ef

Average nergy release / fission	

E f = ∑ α k (t) Ek
Bugey k+ ∑ (α kDC (t)− α kBugey (t) ) σ f k
k

BGY4	

∞

€

difference between 	

BGY4 and DC	

σ f k = ∫ dE ⋅ Sk (E) ⋅ σ IBD (E)
0

43

€

σf = σfk=235U, 239Pu, 241Pu, 238U	
αk: relative fission rate	

Detected ! ( fission-1 MeV -1 x10 )

N

exp
ν

2.5

241Pu
2

239Pu
235U

1.5

1

0.5

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0

2

3

4

5

41

6
7
8
9
! kinetic energy (MeV)Relative Fission Rate	

Opeartion Power	

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Expected Event Rate and Error

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Systematic error summary	Event Selection	

Efficiency	

error	

Event selection	

4121 events	

1.0%	

Background	

355 events	

3.0%	

Spill in/out	+1.4%	

0.4%	4344 events	

1.7%	

Energy response	

-	

1.7%	

# of proton	

-	

0.3%	

Expected Event rate	

Total	

N
N

Observed 4121
Expected 4344

4.0%	

obs
ν
exp
ν

rate analysis	
N obs − N BKG 4121− 335
1==±± 0.027 2 + 0.032
N exp − N BKG 4344 − 335
4121= 0.944 ± 0.016 ± 0.040

120329€sin 2 2θ13 = 0.104 ± 0.030(stat.) ± 0.076(syst.)
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Spectrum analysis	

Best fit: sin22θ13 = 0.086±0.041(stat.)±0.030(syst.)
χ2/DOF = 23.7/17 (best fit); 26.6/18 (sin22θ13=0)
sin22θ13=0 excluded at 94.6%C.L.
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9/Nov./2011 1st result was shown@ LowNu conference Korea

Paper is accepted by PRL	120329suekane@ICRR

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Press conference and news on TVs and news papers	

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Comparison with other θ13 measurements	
  MINOS: PRL 107, 181802 (2011)
T2K: PRL 107, 041801 (2011)
Double Chooz: arXiv:1112.6353 [hep-ex]
DayaBay: rXiv:1203.1669 [hep-ex]

MINOS	

Normal hierarchy	
  Inverted hierarchy	
  
NH	
  

T2K	

IH	
  

sin22θ23=1.0	
  δCP=0	
  任意のδCP	
  Double Chooz	

Daya Bay	  
68% C.L.	
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1st View of Reactor-Accelerator complementarity	

written by handand not precise	

T2K	

120329(Double Chooz	

Daya Bay)	

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Unique features of Double Chooz	
  Double Chooz

Daya BayRENO

923 m.w.e	  120 m.w.e	  291 m.w.e	
  

400m	
  

2.9GWth	  300m.w.e	
  P=8.5GWth (2基)
L=1.05km
M=10ton481m	
  2.3GWth	
  

5m	
  

1,050m	
  1,98

4.25GWth	
  230 m.w.e	  255 m.w.e	
  
360m	
  

P=17.4GWth (6基)
L~1.8km
M=20ton x 4675m.w.e	
  P=16.1GWth (6基)
L~1.4km
M=20ton* Baseline is shortest  reactor complementarity* # of reactor is only 2  direct background measurement	
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Measurement of L dependence of oscillation 	  Double Chooz now	  RENO FD	  120329suekane@ICRR

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Measurement of L dependence of oscillation 	  Double Chooz expected（３years with Far&Near）	
  DC errors assuming• 0.5% uncorrelated syst. errors• Stat. error for 3 years observation	
  RENO FD	  120329suekane@ICRR

52(DB error 	will reduce 	also)	

Measurement of |Δm213| 	

by combination of reactor experiments	

(DC & DB results use |Δm232|)	

3σ	

2σ	

1σ	
  

Double Chooz	  Daya Bay	
  δP=0.5%	
  δΔm132~10% 	

2
Δm23− Δm1322Δm23120329Δm122
Any significant~ cos 2θ12
~
±1%
<<
10%
Δm132
Difference=> new physics	
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Double Chooz Near Lab.
2012 Near detector construction2013 Data taking with Near + Far	
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12/2011	What reactor neutrino could do in the future? 	
KamLAND

precise θ13
Chooz, PaloVerde
DoubleChooz, RENO, Dayabay	

Δm212, θ12

Reactor Neutrino Oscillation
sin22θ13=0.1 assumed

1.2

P(!e --> !e )

1
0.8
0.6

Normal Hierarchy

0.4

Inverted Hierarchy

0.2
No experiment yet	

0
1

Δm213

10

100

No experiment yet	

1000

L(km)

Very precise θ12
Mass Hierarchy
080520120329suekane@ICRR

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More Precise sin22θ13
Very high statistics  sin22θ13 can be measured from distortionof spectrum precisely

P.Hauber et al. hrp-ph/0303232	

DC

120329	RENO

DB

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1000ton x 20GW x 5year

Early "δ" detetion by Accelerator+ Reactor	νeν mode operation of accelerator 	
PAC (ν µ → ν e ) ~ 0.5sin 2 2θ13 − 0.05sin2θ13sinδ
≡ 0.5sin 2 2θ13AC
Reactor measurement	PRE (ν e → ν e ) = 1- sin 2 2θ13 ≡ 1- sin 2 2θ13RE
Difference between reactor θ13 & 	

accelerator θ13 indicates sinδ	

€
2
RE
2
AC
sin δ ~ 30 × (sin 2θ13 − sin 2θ€
13 )

€

€

1203292
E Δm23
~
L
2π

νµ
ν€µ

ντ
ντ
2
E Δm23
~
L €2π

ν€

€
May be possible to identify finite δ 	

before ν mode operation which costs $$$ 	

€ν

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νe
57

€

Parameter region to determine non-0 δ	
加速器	

原子炉	

10ton x 20GW x 5year	

100ton x 20GW x 5year	

Determine	

Determine	

H.Sugiyama hep-ph/0411209v1	

If sin22θ13>0.05 there is a possibility to determine non-0 δ120329	suekane@ICRR	

58	

Mass Hierarchy determination at 50km	
Principle	
Petcov et al., Phys. Lett. B 533, 94 (2002)
S.Choubey et al., Phys. Rev. D 68,113006 (2003)
J. Learned et al., hep-ex/062022
L.Zhan et al., hep-ex/0807.3203
M.Batygov et al., hep-ex/0810.2508
etc.

2
2
2
2
∝
sin
2
θ
sin
Δ
+
tan
θ
sin
Δ 32 )
Ripple	13 (31
12

It is essential that θ12 is not maximum (tan2θ12~0.4) 	
2
2
ω
=
Δm
,
Δm
Foueier analysis will show peaks at
31
32 	
2
2
€ is Δm32
Smaller peaklarger peak is Δm	
 31 ,Where is 	ΔΔ
optimam L?	

ω	:NormalHierarchy	

Power	€
Need more 	

Δ€€:
Inverted
Hierarchy	 study.	

Δ
ω	

32	

31	

32	

12032931	

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Precise θ12 @50km
P(ν e → ν e ) ~ cos 4 θ13 (1− sin 2 2θ12 sin 2 Δ 21 )at 50km, ~80% of ν disappears due to N.O.
 A high sensitivity θ12 measurement is possible.	
€

H.Minakata, hep-ph/07-1070	

1kton x25GW x2.5y	δ sin 2 θ12~ 2.4%(1σ )2sin θ12Current Global fit	δ sin2 θ12~ 6.3%(1σ )sin2 θ12€120329suekane@ICRR€

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Settlement of θ23 Degeneracy	P (ν µ → ν e )K.Hiraide, et al. PRD73, 093008(2006)	

Accelerator
4MW*0.54Mt
2+6years	

sin2Θ23	

€Reactor:100t * 20GW *5y€120329Accelerator Only	€

P (ν µ → ν µ )Accelerator+Reactor	P (ν e → ν e )

DC	

DB	

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Conclusions	* 1st positive neutrino oscillation result from short baseline	experiment. 	

sin22θ13 = 0.086±0.041(stat.)±0.030(syst.) (rate+shape)	

θ13=0 is excluded with 94.6%CL	

* Near Detector will be in operation in 2013.	

sin22θ13 error will be ±0.02	

* Relatively large θ13 opens up next round neutrino studies.	

Combinations of reactor and accelerator experiments 	

will work effectively.
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