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Daya Bay and Other Reactor Neutrino Oscillation Experiments

Jen-Chieh Peng

International Workshop on “High Energy Physics in the LHC Era” Valparaiso, Chile,

December 11-15, 2006

University of Illinois at Urbana-Champaign

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Outline

13 Physics case for a precise measurement

Status and plan for the Daya Bay neutrinos

oscillation experiment

Other reactor neutrino oscillation experiments

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What we have learned from neutrino oscillation experiments

2 2 2 5 221 2 1

2 2 2 3 232 3 2

e 12 13 12 13 13

12 23 12 2

(7.9 0.7) 10 ev (90%c.l.)

| | | | (2.4 0.6) 10

1) Neutrinos are massive

2) Neutrinos do mix with each ot

ev (90% )

e

c.l.

h ri

m m m

m m m

c c s c s e

s c c s

1

3 13 12 23 12 23 13 23 13 2

12 23 12 23 13 12 23 12 23 13 23 13 3

12 23 3

3 1

1

12 2 3

( cos , sin )

13 , 2.

34 , 45 , 13 for the l

2 , 0

epton MNSP Matrix

i i

i i

ij ij ij ij

s e c c s s s e s c

s s c c s e c s s c s e c c

c s

3) Neutrino masses and mixings have provided clear evidence for

physic

.22 for the quark C

s beyond the Stand

KM Matrix

ard Model

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What we do not know about the neutrinos

• Dirac or Majorana neutrinos?

• Mass hierachy and values of the masses?

• Existence of sterile neutrinos?

• Value of the θ13 mixing angle?

• Values of CP-violation phases?

• Origins of the neutrino masses?

• Other unknown unknowns …..

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What we know and do not know about the neutrinos

e 12 13 12 13 1

12 23 12 23 12 23 12 23 23 13 2

12 23 12 23 12 23

13

13

12 23 23 1

3

3

1

13 13 3

i

i i

i i

s e

s e s e

s

c c s c

s c c s c c s s s c

s s c c c se sc ces c

• What is the νe fraction of ν3? (proportional to sin2θ13)

• Contributions from the CP-phase δ to the flavor compositions of neutrino mass eigenstates depend on sin2θ13)

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Why measuring θ13?

A measurement of sin22θ13 at the sensitivity level of 0.01 can rule out at least half of the models!

• Models based on the Grand Unified Theories in general give relatively large θ13

• Models based on leptonic symmetries predict small θ13

A recent tabulation of predictions of 63 neutrino mass models on sin2θ13

(hep-ph/0608137)

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Why measuring θ13?

A measurement of sin22θ13 AND the mass hierarchy can rule out even more models!

A recent tabulation of predictions of 63 neutrino mass models on sin2θ13

(hep-ph/0608137)

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Why measuring θ13? Leptonic CP violation

212 12 13 13 23 23

2 2213 2312

( ) ( ) 16

sin sin sin sin4 4 4

e eP P s c s c s c

m mmL L L

E E E

If sin22θ13>0.02-0.03, then NOvA+T2K will have good coverage on CP δ.

Reactor experiments sets the scale for future studies

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Current Knowledge of 13

Direct search

At m231 = 2.5 103 eV2,

sin22 < 0.17

allowed region

Fogli etal., hep-ph/0506083

Global fit

sin2213 < 0.11 (90% CL)

Best fit value of m232 = 2.4 103

eV2

sin2213 = 0.04

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decay pipehorn absorbertargetp detector

+

+ +

Method 1: Accelerator Experiments

Method 2: Reactor Experiments

Pe sin2 213sin2 223sin2 m31

2L

4E

...

Pee 1 sin2 213sin2 m31

2L

4E

cos4 13sin2 212sin2 m21

2L

4E

• e X disappearance experiment• baseline O(1 km), no matter effect, no ambiguity • relatively cheap

• e appearance experiment• need other mixing parameters to extract 13

• baseline O(100-1000 km), matter effects present • expensive

Some Methods For Determining 13

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Discovery of the Neutrino – 1956

F. Reines, Nobel Lecture, 1995

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Detecting : Inverse Decay

e p e+ + n (prompt)

+ p D + (2.2 MeV) (delayed) + Gd Gd*

Gd + ’s(8 MeV) (delayed)

• Time- and energy-tagged signal is a good tool to suppress background events.

• Energy of e is given by:

E Te+ + Tn + (mn - mp) + m e+ Te+ + 1.8

MeV 10-40 keV

• The reaction is the inverse -decay in 0.1% Gd-doped liquid scintillator:

Arb

itra

ry

Flux Cross

Sectio

n

Observable Spectrum

From Bemporad, Gratta and Vogel

0.3b

50,000b

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Measuring 13 with Reactor NeutrinosSearch for 13 in new oscillation experiment

~1-1.8 km

> 0.1 km

24 2 2 21

13

22 2 31

13 12cos sin 2sin 2 si sin4

1 n4ee

m L

E

mP

L

E

13

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

0.1 1 10 100

Nos

c/Nn

o_os

c

Baseline (km)

Large-amplitudeoscillation due to 12

Small-amplitude oscillation due to 13 integrated over E

m213≈ m2

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detector 1 detector 2

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Results from Chooz

5-ton 0.1% Gd-loaded liquid scintillatorto detect e + p e+ + n

L = 1.05 km

D = 300 mwe

P = 8.4 GWth

Rate: ~5 evts/day/ton (full power) including 0.2-0.4 bkg/day/ton

~3000 e candidates(included 10% bkg) in335 days

Systematic uncertainties

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• Increase statistics:– Use more powerful nuclear reactors

– Utilize larger target mass, hence larger detectors

• Suppress background:– Go deeper underground to gain overburden for reducing cosmogenic background

• Reduce systematic uncertainties:– Reactor-related:

• Optimize baseline for best sensitivity and smaller reactor-related errors

• Near and far detectors to minimize reactor-related errors– Detector-related:

• Use “Identical” pairs of detectors to do relative measurement

• Comprehensive program in calibration/monitoring of detectors

• Interchange near and far detectors (optional)

How to Reach a Precision of 0.01 in sin2213?

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World of Proposed Reactor Neutrino Experiments

Angra, Brazil

Diablo Canyon, USA

Braidwood, USAChooz, France Krasnoyasrk, Russia

Kashiwazaki, Japan

RENO, Korea

Daya Bay, China

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Ref: Marteyamov et al, hep-ex/0211070

Reactor

~20000 ev/year~1.5 x 106 ev/year

Reactor 13 Experiment at Krasnoyarsk, Russia

Original ideal, first proposed at Neutrino2000

Krasnoyarsk- underground reactor- detector locations determined by infrastructure

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KASKA at Kashiwazaki, Japan

near near

far

70 m 70 m

200-300 m

- 7 nuclear power stations, World’s most powerful reactors - requires construction of underground shaft for detectors

Kashiwazaki-KariwaNuclear Power Station

6 m shaft hole,

200-300 m depth See poster by F. Suekane

sin2(213) < 0.02http://kaska.hep.sc.niigata-u.ac.jp/

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North America (13)(46)

BNL, Caltech, LBNL, Iowa state Univ.

Illinois Inst. Tech., Princeton, RPI,

UC-Berkeley, UCLA, Univ. of Houston,

Univ. of Wisconsin, Virginia Tech.,

Univ. of Illinois-Urbana-Champaign,

Asia (13) (70)IHEP, CIAE,Tsinghua Univ.

Zhongshan Univ.,Nankai Univ.Beijing Normal Univ., Nanjing Univ.

Shenzhen Univ., Hong Kong Univ.Chinese Hong Kong Univ.

Taiwan Univ., Chiao Tung Univ.,National United Univ.

Europe (3) (9)

JINR, Dubna, Russia

Kurchatov Institute, Russia

Charles University, Czech Republic

Daya Bay collaboration

~ 125 collaborators

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Location of Daya Bay• 45 km from Shenzhen

• 55 km from Hong Kong

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Ling Ao II NPP:2 2.9 GWth

Ready by 2010-2011

Ling Ao NPP:2 2.9 GWth

Daya Bay NPP:2 2.9 GWth

1 GWth generates 2 × 1020 e per sec

The Daya Bay Nuclear Power Complex• 12th most powerful in the world (11.6 GWth)• Fifth most powerful by 2011 (17.4 GWth)• Adjacent to mountain, easy to construct tunnels to reach underground labs with sufficient overburden to suppress cosmic rays

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Daya BayNPP

Ling AoNPP

Ling Ao-ll NPP(under const.)

Empty detectors: moved to underground halls through access tunnel.Filled detectors: transported between underground halls via horizontal tunnels.

Total length: ~3100 m

295 m

81

0 m

465 m

900 m

Daya Bay Near363 m from Daya BayOverburden: 98 m

Ling Ao Near~500 m from Ling AoOverburden: 112 m

Far site1615 m from Ling Ao1985 m from DayaOverburden: 350 m

entrance

Filling hall

Mid site 873 m from Ling Ao1156 m from DayaOverburden: 208 m

Constructiontunnel

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Conceptual design of the tunnel and the Site investigation including bore holes completed

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Tunnel construction• The tunnel length is about 3000m

• Local railway construction company has a lot of experience (similar cross section)

• Cost estimate by professionals, ~ 3K $/m

• Construction time is ~ 15-24 months

• A similar tunnel on site as a reference

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Antineutrino Detectors• Three-zone cylindrical detector design

– Target zone, gamma catcher zone (liquid scintillator), buffer zone (mineral oil)– Gamma catcher detects gamma rays that leak out

• 0.1% Gd-loaded liquid scintillator as target material

– Short capture time and high released energy from capture, good for suppressing background

• Eight ‘identical’ detector modules, each with 20 ton target mass

– ‘Identical’ modules help to reduce detector-related systematic uncertainties

– Modules can cross check the performance of each other when they are brought to the same location

20 ton0.1% Gd-LS

catcherbuffer

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Event Rates per Detector ModuleSource Units DB LA far Use

Antineutrino Signal (day-1) 930 760 90 signal

Radioactive Backgrounds (Hz) 30 30 30 e+-thresh.

Rock (Hz) 4 4 4

PMT glass (Hz) 8 8 8

other materials (steel) (Hz) 18 18 18

Gd contamination (Hz) 1 1 1

Muons (Hz) 24 14 1

Single neutron (day-1) 9000 6000 400 cal.

Tagged single neutron (day-1) 480 320 45 cal./bkg.

Tagged fast neutron (day-1) 20 13 2 Bkg est

emitters (6-10 MeV) (day-1) 210 140 15 n-thresh.

12B (day-1) 400 270 28 cal.

8He+9Li (day-1) 4 3 0 Bkg

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High light transmission = high optical attenuation length (low optical absorbance).

High light output in the Liquid Scintillator, LS. Long-term chemical stability, since the

experiment will go on for at least 3 years. Stability of the LS means no development of

color; no colloids, particulates, cloudiness, nor precipitation; no gel formation; no changes in optical properties.

Key Requirements for Gd-LS for Daya Bay

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BNL Gd-LS Optical Attenuation: Stable So Far ~700 days- Gd-carboxylate in PC-based LS stable for ~2 years. - Attenuation Length >15m (for abs < 0.003).- Promising data for Linear Alkyl Benzene, LAB (LAB use suggested by SNO+ experiment).

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Detector Prototype at IHEP• 0.5 ton prototype

(currently unloaded liquid scintillator)• 45 8” EMI 9350 PMTs:

14% effective photocathode coverage with top/bottom reflectors

• ~240 photoelectron per MeV :

9%/E(MeV)

prototype detector at IHEP

En

erg

y R

eso

lutio

n

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Background Sources1. Natural Radioactivity: PMT glass, steel, rock, radon in the air, etc

2. Slow and fast neutrons produced in rock & shield by cosmic muons

3. Muon-induced cosmogenic isotopes: 8He/9Li which can -n decay

- Cross section measured at CERN (Hagner et. al.)

- Can be measured in-situ, even for near detectors with muon rate ~ 10 Hz

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355 m

98 m

112 m208 m

Cosmic-ray Muon• Use a modified Geiser parametrization for cosmic-ray flux at surface• Apply MUSIC and mountain profile to estimate muon intensity & energy

DY

B

Ling

Ao

Mid Far

Overburden (m) 98 112 208 355

Muon intensity

(Hz/m2)

1.16 0.73 0.17 0.041

Mean Energy (GeV) 55 60 97 138

Daya BayLing Ao

Far

Mid

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Muon Veto System

•Water shield also serves as a Cherenkov counter for tagging muons

• Water Cherenkov modules along the walls and floor

•Augmented with a muon tracker: RPCs

•Combined efficiency of Cherenkov and tracker > 99.5% with error measured to better than 0.25%

(Water buffer + water cherenkov + RPC tracker)

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Summary of Systematic Uncertainties

sources Uncertainty

Reactors 0.087% (4 cores)

0.13% (6 cores)

Detector

(per module)

0.38% (baseline)

0.18% (goal)

Backgrounds 0.32% (Daya Bay near)

0.22% (Ling Ao near)

0.22% (far)

Signal statistics 0.2%

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Funding and other supports• Funding Committed from

• Chinese Academy of Sciences, • Ministry of Science and Technology• Natural Science Foundation of China• China Guangdong Nuclear Power Group• Shenzhen municipal government• Guangdong provincial government

• Gained strong support from:•China Guangdong Nuclear Power Group•China atomic energy agency•China nuclear safety agency

• Supported by BNL/LBNL seed funds • Supported by DOE $800K R&D fund• Support by funding agencies from other countries & regions• China plans to provide civil construction and ~half of the detector systems; U.S.plans to bear ~half of the detector cost

IHEP & CGNPG

IHEP & LBNL

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Schedule

• begin civil construction April 2007

• Bring up the first pair of detectors Jun 2009

• Begin data taking with the Near-Mid configuration Sept 2009

• Begin data taking with the Near-Far configuration Jun 2010

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Sensitivity to Sin2213

Other physics capabilities:Supernova watch, Sterile neutrinos, …

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Double Chooz

Sensitivity

sin2(213) < 0.03 at 90% CL

after 3 yrs, matm2 = 2 x 10-3 eV2

0.1-0.2 km1.05 km

10 tons detectors8.4 GWth reactor power300 mwe overburden at far site60 mwe overburden at near site

http://doublechooz.in2p3.fr/

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Reactor Experiment for Neutrino Oscillations (RENO) at YongGwang, Korea

Near Detector

Far Detector

~1.5 km150m

(88m high)

Tunnel length: ~600m

Tunnel length: ~100m

(260m high)

20tons (fid. vol.) of liquid scintillator detectors

3 nearest detectors of 200~300kg scintillators

Begin of data taking 2009/2010

sin2(213) < 0.02

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Prospects for a Reactor Measurement of sin2213

Angra, Brazil sin2213 < 0.005- R&D on reactor monitoring. Proposal for 13 measurement after Double Chooz.

Daya Bay, China sin2213 < 0.01- Approved by the Chinese Academy of Science for 50M RMB.- Other Chinese agencies are expected to contribute ~100M RMB.- US DOE has provided 0.8M$ for R&D for FY06. Working towards US project start in FY08.- Plan to start near-mid data taking in 2009, and begin full operation in 2010.

Double-CHOOZ, France sin2213 < 0.03- Funding committment in France and Germany.- Begin running far detector in 2008.- Complete near detector in 2009.

RENO, Korea sin2213 < 0.02- Approved by Ministry of Science and Technology for US $9M. R&D program starting.- Plan to begin data taking in 2009/2010.

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1980s & 1990s Reactor neutrino flux

measurements in U.S. and Europe

2002 Discovery of reactor

antineutrino oscillation

2006 and beyondPrecision measurement of 13

Exploring feasibility of CP violation studies

Past ExperimentsHanfordSavannah RiverILL, FranceBugey, FranceRovno, RussiaGoesgen, SwitzerlandKrasnoyark, RussiaPalo VerdeChooz, FranceReactors in Japan

1995Nobel Prize to Fred Reines

at UC Irvine

Neutrino Physics at Reactors

1956 First observation of neutrinos

44S. Glashow