The Daya Bay Experiment to Measure 13

The Daya Bay Experimentto Measure 13

Herbert Steiner UC Berkeley & LBNL

On behalf of the Daya Bay Collaboration

Presented at the Erice School/Workshop on "Neutrinos in Cosmology,in Astro, in Particle and in Nuclear Physics”

Erice/Sicily/Italy, September 21, 2009

Outline• Overview• Physics• Detector• Backgrounds• Calibration• Schedule

The Daya Bay CollaborationEurope (3) (9)

JINR, Dubna, RussiaKurchatov Institute, RussiaCharles University, Czech

Republic

North America (15)(~89)BNL, Caltech, Cincinnati,

George Mason Univ., 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 (19) (~135)IHEP, Beijing Normal Univ., Chengdu

Univ. of Sci. and Tech., CGNPG, CIAE,

Dongguan Polytech. Univ., Nanjing Univ., Nankai

Univ., Shandong Univ., Shanghai Jiaotong

Univ., Shenzhen Univ., Tsinghua Univ., USTC, Zhongshan Univ., Univ.

of Hong Kong,Chinese Univ. of Hong Kong,

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

~ 233 collaborators

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55 km

45 km

Location of the Daya Bay Nuclear Power Plant

1 GWth generates 2 × 1020 e per sec

The Daya Bay Nuclear Power Plant

•12th most powerful in the world (11.6 GW)• Top five most powerful by 2011 (17.4 GW)• Adjacent to mountain, easy to construct tunnels to reach underground labs with sufficient overburden to suppress cosmic rays

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Total length: ~3100 mDaya Bay

NPP, 22.9 GW

Ling AoNPP, 22.9 GW

Ling Ao-ll NPP(under construction)

22.9 GW in 2010

295 m Daya Bay Near site363 m from Daya BayOverburden: 98 m

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

4 x 20 tons target mass at far site

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

810 m

465 m900 m

entranceFilling hall

Constructiontunnel

Water hall

Daya Bay Layout

Horizontal TunnelTotal length 3200 m

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Excellent overburden to reduce cosmogenic background

Baselines (m):TopographyQuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.

Tunnel Construction Status (July ‘09)

Ling Ao Hall Tunnel Entrance

Far Hall

Daya Bay Near HallConstruction Tunnel

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Position SensitivityQuickTime™ and aTIFF (Uncompressed) decompressor

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How to measure 13?

Measured ratio of Rates

Proton Number

Ratio

DetectorEfficiency

Ratio

sin2213Filling Gd-LS and

Mass measurementCalibration Systems

MethodQuickTime™ and aTIFF (Uncompressed) decompressor

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Daya Bay: Goal and Approach• Utilize the Daya Bay nuclear power complex to:

determine sin2213 with a sensitivity of 0.01 by measuring deficit in e rate and spectral distortion.

0.985

0.99

0.995

1

0 1 2 3 4 5 6 7 8

Ratio(1.8 km/Predicted from 0.3 km)

Prompt Energy (MeV)

sin2213 = 0.01

2 3 4 5 6 7 8 9 10

energy (MeV)

Reduce systematic uncertainties: Reactor-related:

Optimize baseline for best sensitivity and lowest residual errors

Near and far detectors to minimize reactor-related errors

Detector-related: Use “Identical” pairs of detectors to do relative

measurement Fill all detectors with same batch of Gd-LS.

Comprehensive program in calibration/monitoring Side-by-side calibration

Background-related Go as deep as possible to reduce cosmic-induced

backgrounds Enough active and passive shielding

B/S ~0.4% Near B/S ~0.2% Far

How to measure sin2213 to 0.01QuickTime™ and aTIFF (Uncompressed) decompressor

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Sensitivity of Daya Bay

sin2213 < 0.01 @ 90% CL in 3 years of data taking

0 1 2 3 4 5

0.05

0.04

0.03

0.02

0.01

0.

Number of years of data taking

Sensitivity in sin

2 2 1

3 (90%CL)

0.38% relative detector syst. uncertaintym2

31 = 2.5 103 eV2

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Reactor e• Fission processes in nuclear reactors produce

a huge number of low-energy e

e/MeV/

fisson

Resultant e spectrumknown to ~1%

3 GWth generates 6 x 1020 e per sec

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Detecting e in liquid scintillator

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.

• Detect inverse -decay reaction in 0.1% Gd-doped liquid scintillator:

0.3b

50,000b

• Energy of e is given by:

E Te+ + Tn + (mn - mp) + m e+ Te+ + 1.8 MeV 10-40 keV

Detection of e

Coincidence of prompt positron and delayed neutron signals

helps to suppress background events

Inverse -decay in Gd-doped liquid scintillator:Delayed Energy Signal Prompt Energy Signal

.

1 MeV 8 MeV 6 MeV 10 MeV

• Ee+(“prompt”) [1,8] MeV • En-cap (“delayed”) [6,10] MeV

• tdelayed-tprompt [0.3,200] s

n-p n-Gd

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Site RateDYB 840LA 740Far 90

Expected Antineutrino Rates(Per Day per Module)

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Systematic Uncertainty Control

Sources of UncertaintyQuickTime™ and aTIFF (Uncompressed) decompressor

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BackgroundsQuickTime™ and aTIFF (Uncompressed) decompressor

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740

Layout in DBY HallQuickTime™ and aTIFF (Uncompressed) decompressor

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Daya Bay Antineutrino Detector

• 8 “identical”, 3-zone detectors

target mass: 20t per detectordetector mass: ~ 110tphotosensors: 192 PMTsenergy resolution: 12%/√E

e + p → e+ + n

acrylic tanksphotomultipliers

steel tank

calibration system

Gd-doped liquid scintillator

liquid scintillator

mineral oil

Gd-Liquid Scintillator Test Production

500L fluor-LABTwo 1000L 0.5% Gd-LAB 5000L 0.1% Gd-

LS

0.1% Gd-LS in 5000L tank

Daya Bay experiment uses 200 ton 0.1% gadolinium-loaded liquid scintillator (Gd-LS). Gd-TMHA + LAB + 3g/L PPO + 15mg/L bis-MSB

4-ton test batch production in April 2009.Gd-LS will be produced in multiple batches but mixed in reservoir on-site, to ensure identical detectors.

Gd-LS stability in prototype

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Water Cherenkov Detector to Tag MuonsQuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.

CalibrationQuickTime™ and aTIFF (Uncompressed) decompressor

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FEE ANALOG CIRCUITS

INPUT STAGE

FAST ANALOG CIRCUIT for Analog Trigger

THRESHOLD CIRCUIT for Multiplicity Trigger

SHAPING & ADC CIRCUIT for Charge Measurement

Front End ElectronicsQuickTime™ and aTIFF (Uncompressed) decompressor

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Civil Construction

Control Room

Surface Assembly BldgEntrance

Inside tunnel

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Tunnel Construction Status

Pool Excavation in DBY Hall - Aug 09 Main Tunnels Join - June 09

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Detector Assembly

4-m vessel in the U.S.

Stainless steel tank in China

3-m acrylic vessel in Taiwan

SS Tank delivery Delivery of 4m AV Stainless steel tank in SAB

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AD Components QuickTime™ and aTIFF (Uncompressed) decompressor

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4-meter acrylic vessel arrives Unpacked 4-m acrylic vessel

PMT Ladder Mounting of non-refecting panelson ladder

AD AssemblyQuickTime™ and a

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Schedule• 2003-2007: Proposal, R&D, engineering design etc.• October 2007: Ground Breaking • March 2009: Surface Assembly Building occupancy • Fall 2010: Daya Bay Near Hall ready for data taking • Fall 2011: All near and far halls ready for data taking

Three years’ data taking to reach full sensitivity.

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Thank You !

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