θ13 Measurements with Reactor Antineutrinos and the KASKA experiment
WIN’05 Neutrino Working Group
Delphi Greece
onJune 8th, 2005
Y.Fukuda
for the KASKA collaboration

Miyagi University of Education

Understanding of Neutrino Sector
 Pontecorvo-Maki-Nakagawa-Sakata mixing
matrix (leptonic version of CKM matrix)νe νµ ντ : flavor eigenstateν1 ν2 ν3 : mass eigenstateSK(atmν)+ K2K
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Solarν +KL
Weak Interactions and Neutrinos
2005 (WIN05)

2Unknown (1-3) sector
 Current status

Next important step is to measure θ13cf. finite value of sin22θ13 indicates the possibility ofCPV phase δl measurement in the future

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Experimental limits for (1-3) sector
 Experimental upper limit obtained by CHOOZ
reactor experiment:
sin22θ13＜0.2 @ ∆m213=2×10-3eV2

http://www.ifi.unicamp.br/~lenews05/talks/KerretDoubleChooz.pdf

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Measurement of θ13 using by reactor
 Neutrinos from reactor¾ Nuclear fission produce ~ 6νeby β-decay¾ Usual 1GW reactor emits
6×1020 νe /sec
¾ Neutrino energy spectrum
determined by spallation
products data with 2.5%
accuracy¾ Neutrino absorption byprotonνe+p →e++n (Ee=Eν-1.8MeV)
e++e- → 2γ (0.511MeV)
Esignal=Eν – 0.8MeV>1.0MeV
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~4MeV

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How to measure the θ13
 Disappearance νe from reactor

P(νe→νe)=1-sin22θ13sin2(∆m213L/4E)+O(10-3) (as ∆m12~solarν )cf. E=4MeV and sin22θ13=0.1

νe→ντνe→νµ1.2
113

0.8

Measure this small deficit.
Due to ∆m212<∆m223(13),this is almost pure θ13
measurement

P(νe→νe)sin22θ

sin2θ 13=0.1

0.6
0.4
0.2
00.1

110100

1000

L(km)

Need 1% accuracy
for the measument
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1~2km forreactor νe

Weak Interactions and Neutrinos
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KamLAND6

θ13 projects
http://www.ifi.unicamp.br/~lene05/talks/Freedman_DeyaBay.ppt

Diablo Canyon, CA

Kashiwazaki (KASKA), JapanChooz, France

Daya Bay, China

Angra dos Reis , Brasil

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Braidwood

Young Gwang, Korea

7

Summary for θ13 project Characteristics
meritdemerit

sensitivity¾

Double-Chooz old tunnel (realistic) ,know how

L might short
0.02@σsys
systematic error? ~0.6% 5yrs

¾KASKAlargest reactor, small
detector, know how

man power?
budget?

0.015@σsys~0.5% 3yrs¾

Braidwoodlarge and movabledetector (cross calib.)
Daya-bay
cheep construction
cost (tunnel etc)
Angra?
Young Gwang?

security?
expensive?
budget?

< 0.01
shape+cnt.
~0.01

¾¾
¾

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Funding?
?

Weak Interactions and Neutrinos
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8KASKA experiment
http://www.jp.wikipedia.org

 Kashiwazaki –Kariwa
nuclear power station¾ Largest power in theworld (24.3GW)¾ 7 reactors in two cluster
Kashiwazaki-Kariwa（日）The world’s most powerfulreactor complex

CHOOZ（仏）DiabloCanyon（米）Braidwood（米）DayaBay（中）P=24.3GWthAngora（ブラジル）
Krasnoyarsk（露）Young Gwang

051015202530

Site Power (GWth)

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Weak Interactions and Neutrinos2005 (WIN05)

9KASKA collaboration list
Niigata University: N.Tamura, M.Tanimoto, H.Miyata, H.Nakano
T.Kawasaki, M.Katsumata, R.Watanabe, T.Iwabuchi, M.Sasaki,M.Aoki, K.Sakai
Tohoku University: F.Suekane, Y.Sakamoto, Y.Tsuchiya
Tokyo Metropolitan University: T.Sumiyoshi, H.Minakata, O.Yasuda ,T.Matsumoto, K.Sakuma, T.Nakagawa
Tokyo Institute of Technology: M.Kuze, K.Nitta, H.Furuta, J.Maeda
Kobe University: T.Hara
KEK: N.Ishihara, H.Sugiyama
Okayama University: M.Sakuda
Miyagi University of Education: Y.Fukuda
Hiroshima Institute of Technology: Y.Nagasaka

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Geometry of KASKA experiment Location of detectors
Reactor and Detector Locations
2300#51800#6#7

NEAR-B Detector

1300
FAR Detector

800300#4#3

NEAR-A Detector

Far detector is moved to outside of reactor area, so that thebase line could be set at 1.6~ 1.8km#2Reactor-#1-200-500

0500

1000

1500

2000

Relative Position (m)1.6~1.8km
24.3GW~0.4km~0.37km
70m
~50m

150m
8ton

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How to detect anti-νe Absorption by proton via inverse β-decay
νe + p → n + e+e+ + e- → 2γ (Ε=Εν−0.8MeV)
n + Gd → Gd’ + γs (ΣEγ~8MeV)
Cf. KamLAND has no Gd in LS
n + p → d + γ (2.2MeV)

Delayed coincidence candrastically reduce thebackground
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12Detector under the ground Shaft hole
 Aim :To reduce cosmic raybackgrounds
 Measure actual cosmicray BG

6cmcurrent design
Near : ~100HzFar : ~10Hz
LeadShield

Plastic
Scintillators

Hygrometer8th of June, 2005

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KASKA Detector
More bufferLess oil & Less costν detector Gd-LS (11.5m3)=9.2ton (ρ=0.8)
Cosmic ray
trackerγ-catcher LS (70cmt)
Buffer Oil(115cmt)

10”PMT*300, (13”*150)+2”PMT*50

Water

Acrylic vessel
Stainless steel tank

Fe shield(10cmt)
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Fe tank(1cmt)
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Expected sensitivity for KASKA
Expected event rate : 50,000/3years @ far detector
1,200,000events/3years @ near detector precise reactor-ν science(rate only)

σstat ~ 0.5%
(2.8% @CHOOZ)
σsys<1%
2.7%@CHOOZ
If σsys achieves 0.5%,
Sin22θ13<0.015

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Why θ13 with reactor
 Accelerator long-base line experiment : νe appearance(νµ→νe)¾J-PARC –SK(T2K) has
sensitivity sin22θ13 < 0.006
with 5yrs opr.
¾KASKA has sin22θ13~0.02
Conflict them?

 No : νµ→νe appearance
experiment can not measure
pure θ13 (νe disappearance
experiment can do it)
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θ13 measurement by reactor
 Reactor experiment as clean lab.
⎛ ∆m 2 L ⎞⎛ ∆m 2 L ⎞422Pee ≈ 1− sin 2θ13 sin ⎜ 31 ⎟ − cos θ13 sin 2θ12 sin ⎜ 21 ⎟⎝ 4 Eν ⎠⎝ 4 Eν ⎠22O(10-3)¾ νe→νe disappearance experiment¾ Measurement rate (deviated from 1/r2 dependence) andspectral distortion¾ Multi-detectors¾ O(1km) base-line : no matter effect

http://www.ifi.unicamp.br/~lene05/talks/Freedman_DeyaBay.ppt
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θ13 measurement by accelerator
 Intrinsic ambiguity (CP phase)

here, sin2(∆m231L/4E)~1

Munakata, Sugiyma, Yasuda
Phys.Rev.D68(2003)033017

Pµe¾ νµ→νe appearancePµe has ambiguity
due to sinδ
¾ O(100-1000km)
long-baseline :matter effectsin22θ13
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θ13 measurement by accelerator
 Intrinsic ambiguity 2 (θ23 degeneracy)

PµeIf sin22θ23=0.95 then sin2θ23=0.61 or 0.39

J-PARCsensitivity
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Munakata, Sugiyma, Yasuda
Phys.Rev.D68(2003)033017

sin22θ13
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θ13 measurement by reactor and accelerator Both experiments are complementary¾ Both results complete physics issue

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R&D for KASKA project R&D budgets have been approved inJFY2004~2005¾ Boring study at near-B site
¾ Prototype detector¾ Electronics development¾ LS developments (another budget 2005-2006)¾ Detector and Shaft hole design study¾ Cosmic-ray detector development (2005-2006)

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Possible schedule
JFY

2005

2006

2007

2008

N-A

N-B

Far

Cost ? : JFY2005 Budget request ~$30M
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Other reactor θ13 experiment Double CHOOZ

8th of June, 2005

http://www.ifi.unicamp.br/~lenews05/programws05.html/talks/StatusDoubleChooz_Angra.pdf.gz

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Concept of Double Chooz experiment νe disappearanceνe
8.4GW Chooz
PWR stations

νe,µ,τ
Near detector

Far detector¾ Tuned sensitivity by optimal base line and 10t for
far detector (sin22θ13~ 0.018 @1.35km , 0.02 @1.1-1.7km assuming ∆m213=2.8×10-3eV2 + 3years)

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Expected sensitivity
 10t far detector¾ sin22θ13 ~0.02 @ 1.1-1.7km
assuming ∆m213=2.8×10-3eV2+ 3year¾ Flat sensitivity for 100tons,but…
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Improve of Chooz
 Statistical error (σstat= 2.7% @ Chooz)

 Systematic error (σsys = 2.8% @ Chooz)¾ two identical detector
make σrelative=0.6%¾ Dead time ~50% @ neardetector …
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Braidwood
http://mwtheta13.uchicago.edu/

 Experimental site

Braidwood

http://www.ifi.unicamp.br/~lenews05/talks/Stefanski1.ppt
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Detector of Braidwood
 Fiducial volume : 5.2m
radius with Gd-LS
VetoDetectors
 Buffer volume : 7m
radius with mineral oil 1000 8”PMT with 25%
coverage Movable detector (directcross calibration)
 Identify and veto the few
shower producing muons
which produce theneutrons and spallation
products
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Shieldingnpnnµ

6 metersµhttp://www.ifi.unicamp.br/~lenews05/talks/Stefanski1.ppt

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Uncertainty and Sensitivity of Braidwood
 Sensitivity

http://www.ifi.unicamp.br/~lenews05/talks/Stefanski1.ppt

 Unceitainty¾ Calibrate near/far eff. vol…
¾ Multi-layer veto
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Cost estimation and schedule for Braidwood
 Schedule¾ 2004: R&D proposal submission.
¾ 2005: Full proposal submission¾ 2007: Project approval; start construction¾ 2009: Start data-taking

 Cost¾ Estimated 4 detector $18M +$5M = $23M
¾ Estimated civil construction $34M + $8.5M =$42.5M¾ Total : $65.5M
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Daya Bay
 Experiment site
http://www.ifi.unicamp.br/~lenews05/talks/Freedman_DeyaBay.ppt

Concept:¾Minimize correlated BG¾Use horizontal tunnel¾Multi-detectors

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Sensitivity of the Daya Bay
 Baselines at Daya Bay allow near/far and mid/faranalysis¾volume: 5×40 tons
¾shape+rate information¾reactor systematics
mid/far: 0.2%
near/far: 0.08%¾3 years of running(cores 5+6 turn on after 2years)
http://www.ifi.unicamp.br/~lenews05/talks/Freedman_DeyaBay.ppt
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Schedule and status of Daya Bay
 Schedule¾ Summer 2005 completed geological survey¾ 2006
begin civil construction¾ Early 2007
complete tunnels and undergroundlaboratories for near site
¾ 2007
construction of tunnels for mid- and far site
¾ 2008complete tunnels and experimental halls¾ 2008/2009
begin data taking with all facilities operation

 Status¾¾¾¾¾

Good cooperation from the Daya Bay Nuclear power plant.
R&D agreement between US and China.
Have formed a proto-collaboration.
Two collaboration meetings (Dec 2004 and Jan 2005).
LOI / proposal in preparation

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Summary Reactor medium base-line experiment could becomplementary with accelerator long base-line
experiment for θ13 physics.
 Most powerful reactor Kashiwazaki-Kariwa station(Tokyo Electronic Power Co.) agree with our project.
 Collaboration is growing up and welcome to yourparticipation.
 Discussing actual design for 3 identical detector andlocation for far detector, shaft hall, construction
methods…
 Getting R&D fund, need REAL budget!
 KASKA will start from JFY2008, if it’s on schedule
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