The Daya Bay Experiment Steve Kettell BNL 1)Motivation 2)Reactor anti- e 3)Daya Bay Experiment 4)Collaboration/BNL involvement

The Daya Bay Experiment

Steve KettellBNL

1) Motivation2) Reactor anti-e

3) Daya Bay Experiment4) Collaboration/BNL involvement

April 18, 2006 Steve Kettell, BNL DOE HEP Review 2

• Connecting Quarks to the Cosmos: One of the eleven `profound questions’ addresses the mass and mixing of neutrinos. (2003)

• Quantum Universe: “Detailed studies of the properties of neutrinos their masses, how they mix, and whether they are Majorana particles will tell us whether neutrinos conform to the patterns of ordinary matter or whether they are leading us to the discovery of new phenomena.” (2004)

recommendation of the APS Study Group (11/04)•

NuSAG (2/28/06)

Neutrinos

The U.S. should mount one multi-detector reactor experiment sensitive to edisappearance down to sin22θ13 ~ 0.01.


BNL PAC

• BNL High Energy Nuclear Physics Program Advisory Committee meeting 3/23/06

• The BNL neutrino group's presentation of the Daya Bay experiment and their involvement in it was very well received. In particular, the committee noted the crucial role BNL plays in R&D work for the Daya Bay experiment. In conjunction with the BNL Chemistry department, the group studies solubility of Gd in scintillator, and attenuation of light in the Gd doped scintillator. These R&D issues are at the heart of the potential success of both the Daya Bay and Braidwood reactor efforts. The committee recognizes and encourages the great synergy between the BNL physicists and chemists in the reactor program.

• PAC Membership: Stanley Brodsky, Donald Geesaman, Miklos Gyulassy, Barbara Jacak, Peter Jacobs, Bob Jaffe, Takaaki Kajita, James Nagle, Jack Sandweiss, Yannis Semertzidis, (Bonnie Fleming, Frank Sculli)


The Last Unknown Neutrino Mixing Angle: 13

UMNSP MatrixMaki, Nakagawa, Sakata, Pontecorvo

1 0 0

0 cos23 sin23

0 sin23 cos23

cos13 0 e iCP sin13

0 1 0

e iCP sin13 0 cos13

cos12 sin12 0

sin12 cos12 0

0 0 1

1 0 0

0 e i / 2 0

0 0 e i / 2i

What ise fraction of 3?Is there symmetry in neutrino mixing?

Ue3 is the gateway to CP violation in neutrinos.

?

U Ue1 Ue2 Ue 3

U1 U2 U 3

U1 U 2 U 3

0.8 0.5 Ue 3

0.4 0.6 0.7

0.4 0.6 0.7

?

atmospheric, K2K reactor and accelerator 0SNO, solar SK, KamLAND

12 ~ 32° 23 = ~ 45° 13 = ?


Pee 1 sin2 213 sin2 m312L

4E

cos4 13 sin2 212 sin2 m21

2L

4E

Distance (km)

Pee

Pe e

Measuring 13 with Reactor Neutrinos

Search for 13 in oscillation experiment

Ue3

~1.8 km

~ 0.3-0.5 kmPure measurement of 13.

nuclear reactor

detector 1

detector 2

13

Daya Bay, China


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

• Energy of e is given by:

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

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

Arb

itra

ry

Flux Cross

Sectio

n

Observable Spectrum

From Bemporad, Gratta and Vogel

Detection of antineutrinos in liquid scintillator

e p e+ + n (prompt)

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

Gd + ’s(8 MeV) (delayed)

50,000b

0.3b


Current Knowledge of 13

2.7% without near detectors

m

• limited statistics• reactor-related systematic errors: - energy spectrum of e (~2%) - time variation of fuel composition (~1%)• detector-related systematic error (1-2%)• background-related error (1-2%)

Established technique (e.g. Chooz) with improvements for Daya Bay

Limit on from Chooz

At m231 = 2.4 103 eV2,

sin22 < 0.15

allowed region


Requirements for improving the sensitivity to sin2213 0.01

Higher statistics:• More powerful reactor cores• Larger target mass

Better control of systematic errors:• Utilize multiple detectors at different baselines (near and far)

measure RATIOS• Make detectors as nearly IDENTICAL as possible• Careful and thorough calibration and monitoring of each detector• Optimize baseline for best sensitivity and small residual reactor-related errors• Interchange detectors to cancel most detector systematics


Goals And Approach

• Utilize the Daya Bay nuclear power facilities to:- determine sin2213 with a sensitivity of 1%- measure m2

31

• Employ horizontal-access-tunnel scheme:- mature and relatively inexpensive technology- flexible in choosing overburden and baseline- relatively easy and cheap to add experimental halls- easy access to underground experimental facilities - easy to move detectors between different locations with good environmental control.

• Adopt three-zone antineutrino detector design.


Daya Bay, China

55 k

m

45 km


Ling Ao II NPP:2 2.9 GWth

Ready by 2010-2011

Ling Ao NPP:2 2.9 GWth

The Daya Bay Nuclear Power Facilities

Daya Bay NPP:2 2.9 GWth

1 GWth generates 2 × 1020 e per sec

• Powerful facilities (total thermal power):

11.6 GW (now) 17.4 GW (2011)

comparable to Palo Verde, the most powerful nuclear power plant in U.S.• Adjacent to mountain, easy to construct tunnels to underground labs with sufficient overburden to suppress cosmic rays


Daya BayNPP

Ling AoNPP

Ling Ao-ll NPP(under const.)

Entrance portal

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

Total length: ~2700 m

230 m(15% slope)290 m

(8% slope) 73

0 m

570 m

910 m

Daya Bay Near360 m from Daya BayOverburden: 97 m

Ling Ao Near500 m from Ling AoOverburden: 98 m

Far site1600 m from Ling Ao2000 m from DayaOverburden: 350 m

Mid site~1000 m from DayaOverburden: 208 m


buffer

20 tonnes

Gd-LS

gamma catcher

Antineutrino Detector

• Antineutrinos are detected via inverse -decay in Gd-doped liquid scintillator (LS)

Description:• 3 zones: Gd-LS target (20 tonnes), LS gamma catcher, oil buffer• 2 nested acrylic vessels, 1 stainless vessel• 200 8” PMT’s on circumference of 5m 5m cylinder• reflective surfaces on endplates of cylinder• energy resolution is 14%/E


Conceptual Design of Muon Veto

• Detector modules enclosed by 2m of water to shield neutrons (and gamma-rays)

• Water shield also serves as a Cherenkov veto• Augmented with a muon tracker: scintillator or RPC's• Combined efficiency of Cherenkov and tracker > 99.5%

2m ofwater

~0.05

Neutron background vs. thickness of water

water

muon tracker

rock

a conceptual design


Findings of Geotechnical Survey

• No active or large faults

• Earthquakes are infrequent

• Rock: massive and blocky granite

• Rock mass: slightly weathered or fresh

• Groundwater: low flow at tunnel depth

• Quality of rock: stable and hard

Good geotechnical conditions for tunnel construction

Pat Dobson(LBL)

Chris Laughton (FNAL)

Joe Wang(LBL) Yanjun Sheng

(IGG)

U.S. experts in geology andtunnel construction assistgeotechnical survey:

Borehole drilling


Tunnel construction

• The total tunnel length is ~3 km

• Preliminary civil construction design: ~$3K/m

• Construction time is ~24 months (5 m/day)

• A similar tunnel already exists on site

7.2 m

7.2

m


Background

Near Site Far Site

Radioactivity (Hz) <50 <50

Accidental B/S <0.05% <0.05%

Fast neutron B/S 0.14%0.16% 0.08%0.1%8He/9Li B/S 0.41%±0.18% 0.02%±0.08%

• Accidental Background:• Natural Radioactivity: PMT glass, Rock, Radon in the air, etc• Neutrons

• Correlated Background:• Fast neutrons Neutrons produced in rock and water shield (99.5% veto

efficiency)

• Cosmic Ray production of 8He/9Li which can decay via -n emission

For reference, 560(80) neutrino events per detector per day at the near(far) site


Systematic Uncertainty

Systematic error Chooz Daya BayReaction Cross Section 1.9% 0, near-far cancellation

Energy released per fission 0.6% 0, near-far cancellation

Reactor Power 0.7% 0.1%, near-far cancellation

Number of Protons 0.8% 0, detector swapping

Detection efficiency 1.5% ~0.2%, fewer cuts, detector swapping

Total 2.75% ~0.2%

Statistical Error (3 years): 0.2% 2.8% (Chooz) Residual systematic error: ~ 0.2% 2.7%


Sensitivity

Daya Baynear (40t)

Tunnel entrance

Ling Aonear (40t)

Far (80t)

Antineutrino detectormodules, each with 20 tonne target mass

Horizontal tunnel

3-year run with 80 t at far site


The Daya Bay Collaboration: China-Russia-U.S.

X. Guo, N. Wang, R. WangBeijing Normal University, Beijing

L. Hou, B. Xing, Z. ZhouChina Institute of Atomic Energy, Beijing

M.C. Chu, W.K. NgaiChinese University of Hong Kong, Hong Kong

J. Cao, H. Chen, J. Fu, J. Li, X. Li, Y. Lu, Y. Ma, X. Meng, R. Wang, Y. Wang, Z. Wang, Z. Xing, C. Yang, Z. Yao, J. Zhang, Z. Zhang, H. Zhuang, M. Guan, J. Liu, H. Lu, Y. Sun, Z. Wang, L. Wen, L. Zhan, W. ZhongInstitute of High Energy Physics, Beijing

X. Li, Y. Xu, S. JiangNankai University, Tianjin

Y. Chen, H. Niu, L. NiuShenzhen University, Shenzhen

S. Chen, G. Gong, B. Shao, M. Zhong, H. Gong, L. Liang, T. XueTsinghua University, Beijing

K.S. Cheng, J.K.C. Leung, C.S.J. Pun, T. Kwok, R.H.M. Tsang, H.H.C. WongUniversity of Hong Kong, Hong Kong

Z. Li, C. ZhouZhongshan University, Guangzhou

Yu. Gornushkin, R. Leitner, I. Nemchenok, A. Olchevski

Joint Institute of Nuclear Research, Dubna, Russia

V.N. Vyrodov

Kurchatov Institute, Moscow, Russia

B.Y. Hsiung

National Taiwan University, Taipei

M. Bishai, M. Diwan, D. Jaffe, J. Frank, R.L. Hahn, S. Kettell,

L. Littenberg, K. Li, B. Viren, M. Yeh

Brookhaven National Laboratory, Upton, NY 11973-5000, U.S.

R.D. McKeown, C. Mauger, C. Jillings

California Institute of Technology, Pasadena, CA 91125, U.S.

K. Whisnant, B.L. Young

Iowa State University, Ames, Iowa 50011, U.S.

W.R. Edwards, K. Heeger, K.B. Luk

University of California and Lawrence Berkeley National Laboratory, Berkeley, CA 94720, U.S.

V. Ghazikhanian, H.Z. Huang, S. Trentalange, C. Whitten Jr.

University of California, Los Angeles, CA 90095, U.S.

M. Ispiryan, K. Lau, B.W. Mayes, L. Pinsky, G. Xu,

L. Lebanowski

University of Houston, Houston, Texas 77204, U.S.

J.C. PengUniversity of Illinois, Urbana-Champaign, Illinois 61801, U.S.

20 institutions, 89 collaborators



Accomplishments at Feb Collaboration Meeting

• Bylaws were ratified by the collaboration.• Institutional board, with one representative from each member

institution and two spokespersons, was established.• Executive board was established:

Y. Wang (China) A. Olshevski (Russia)C. Yang (China) K.B. Luk (U.S.)M.C. Chu (Hong Kong) R. McKeown (U.S.)Y. Hsiung (Taiwan)

• Scientific spokespersons were chosen:Y. Wang (China), K.B. Luk (U.S.)

• Project management in China and U.S. were compared.• Initial discussions of construction project management.• Task forces were set up. Each task is led by at least one member

from China and one from U.S.


Collaboration Communications

• Weekly collaboration phone meetings

• Weekly U.S. Daya Bay phone meetings

• LBL serves as the hub for both phone meetings

• BNL provides web archive for phone meetings

• Several face-to-face collaboration meetings have been held in Beijing, Shenzhen, Hong Kong, and Berkeley. The most recent one was held at IHEP in February 2006.

• Next collaboration meeting in Beijing, June 9-12, 2006.


Joint U.S.-China Task Forces

1. Antineutrino DetectorCo-Chairs: S. Kettell (BNL, U.S.)

Y. Wang (IHEP, China)

2. Calibration Co-Chairs: R.D. McKeown (Caltech, U.S.)

X. Biao (CIAE, China)

3. CommunicationsCo-Chairs: J. Cao (IHEP, China)

K.M. Heeger (LBNL, U.S.) W. Ngai (CUHK, Hong Kong)

4. Liquid ScintillatorCo-Chairs: R.L. Hahn (BNL, U.S.)

Z. Zhang (IHEP, China) I. Nemchenok (Dubna, Russia)

5. Muon Veto Co-Chairs: L. Littenberg (BNL, U.S.)

K. Lau (Houston, U.S.) Y. Changgen (IHEP, China)

6. Offline Data Distribution and ProcessingCo-Chairs: J. Cao (IHEP)

B. Viren (BNL)

7. Project Management and IntegrationCo-Chairs: B. Edwards (LBNL, U.S.)

S. Kettell (BNL, U.S.) Y. Wang (IHEP, China) H. Zhuang (IHEP, China)

8. Simulation Co-Chairs: J. Cao (IHEP, China)

C. Jillings (Caltech, U.S.)

9. Tunneling and Civil ConstructionLead: C. Yang (IHEP, China)U.S. Consultant: C. Laughton (FNAL, U.S.)

International working groups with U.S.-China co-leadership for main detector systems and R&D issues established at the February collaboration meeting.


Why BNL?

• The Physics is compelling! and a critical step to CP

• BNL provides a strong National Laboratory presence to assure the success of the experiment.

• BNL has a rich and storied tradition in physics: in both the Physics and Chemistry departments

• BNL Chemistry has been involved in liquid scintillator research for Daya Bay for 3 years

• This experiment provides a bridge from the current Physics Department effort on MINOS to a long-baseline effort to measure CP violation in the neutrino sector.


BNL involvement in Daya Bay

• Formally joined collaboration at Feb. 2006 meeting in Beijing• Member of Institutional Board (Kettell)• Lead of liquid scintillator task force (Hahn,Yeh)• Lead of muon veto task force (Littenberg, Diwan, Bishai)• Central detector task force (Kettell)• Simulations task force (Jaffe)• Project and other engineering resources available


• BNL is deeply involved in the muon tracker design

• BNL is working with engineer from LBNL on antineutrino detector design and project management

• BNL is looking to incorporate additional BNL engineering

• One third of R&D request for BNL projects

• As MINOS analysis effort matures, more effort directed to Daya Bay construction project and later to DB analysis

VLBN

MINOS

E734

BNL in Daya Bay


U.S. R&D Plan

Primary R&D Goals:• Ensure a strong U.S. contribution to the

Daya Bay experiment.• Match the schedule of Chinese R&D and

design. Don’t let U.S. slow project down!

• Optimize U.S. scope while minimizing cost.

Full R&D funding in FY06 (and FY07):

• Enable U.S. input to experiment design.

• Timely technology choices.

• Early determination of project cost and schedule.

• Finalize preparations for CD-1 in about six months.

DOE-HEP Daya Bay FY06 R&D Request1/23/06, revised 1/31/06

R&D Tasks FY06 ($k)

1) Simulations 195

2) Liquid Scintillator 255

3) Antineutrino Detector 500

4) Calibration 370

5) Electronics 150

6) Muon Veto 419

7) Site Development 200

8) Project Definition 265

Total 2354


Gd-Loaded Liquid Scintillator

BNL lead role: substantial R&D at BNL on metal loaded LS (funded by ONP + LDRD)• Avoid the chemical/optical degradation problems encountered in the Chooz and Palo Verde

experiments

Primary R&D Goals: • Study alternatives to PC (Low flashpoint: 48oC, health/environmental issues, attack acrylic)

– For example, mixture of 20% PC and 80% dodecane– Current R&D is with Linear Alkyl Benzene, LAB, which is very attractive (high

flashpoint:130o, biodegradable and environmentally friendly, readily available with tons produced by industry for detergents)

• Successfully prepared Gd-LS in 100% LAB, with favorable properties (over Gd in PC)

• Further studies needed to determine stability over time• Develop mass-production techniques to go from the current bench-top scale of kg (several

liters) to tonnes (thousands of liters)

1. Require stable (~years) Gd-LS with high light yield, long attenuation length.2. Explore alternatives to pseudocumene, PC.3. Evaluate chemical compatibility of Gd-LS with acrylic (detector vessel).


Calendar Date

Ab

sorb

ance

at

430

nm

Optical Attenuation of BNL Gd-LS

Gd-LS under UV light (in 10 cm cells)

Stable for ~500 days so far


Muon Veto/Tracker

Understanding muon and spallation backgrounds:

1. High efficiency, redundant muon vetoes.

2. Tracking ability for systematic studies and event identification.

Primary R&D Goals:

• Evaluate candidate technologies for muon tracker:• Plastic scintillator strips• Resistive Plate Chambers• Liquid scintillator modules

• Evaluate candidate technologies for muon veto:• Water pool Cherenkov • Modular water Cherenkov

BNL Role• Subsystem in which U.S. is likely to take the lead BNL has extensive experience in both plastic and liquid scintillator.


Primary R&D Goals:• Mechanical design of central detector.• Design of transportation and installation systems for detectors.• Identify vendors for fabricating acrylic vessels.

BNL Role:• Engineering and leadership experience at LBNL and BNL.

On the critical path (civil construction design contract).

Antineutrino Detector

Measurement of sin2213 0.01 requires detector systems designed tominimize systematic uncertainties.

1. Identical detector modules:• identical scintillator volumes, optical transparency.• facilitate calibration/monitoring system.

2. Moveable detectors: • design detectors for identical performance at all sites.• engineer support and movement structures.• time critical due to close interface with tunnel/cavern design.

KamLAND 2005


Site Development

1. Analyze core samples: input for detailed civil construction design studies.

2. Define surface building and underground halls (space and infrastructure).

3. Define liquid scintillator purification and handling (space and infrastructure).

Primary R&D Goals:• Define underground hall specifications in order to proceed to final civil design contract.• Interface between experiment design and hall design.

BNL Role:• Engineering and physics design experience

• Specification of civil design is on the critical path; minimize delay and reduce risk for civil construction.

KamLAND 2005


Project Definition

1. Develop complete project scope and schedule (joint with China).2. Define U.S. and Chinese deliverables (joint with China).3. Develop U.S. cost and schedule ranges.4. Build U.S. project team and organization.

Primary R&D Goals:• Develop the U.S. project scope, cost and schedule.• Coordinate with China on total project scope, cost and schedule.

BNL Role:• U.S. responsibility. Exploit project experience at LBNL and BNL.

• Continue to develop coordination with Chinese effort.• Develop baseline project.• Develop overall experiment design.

KamLAND 2005


Initial definition of Project Scope

• Muon tracking system (veto system)

• Gd-loaded liquid scintillator

• Calibration systems

• Antinu Detector (Acrylic, PMT’s)

• Electronics/DAQ/trigger hardware

• Detector integration activities

• Project management activities Majority Responsibility

WBS Description China US

4 DAQ, Trigger, Online & Offline Hardware ĆDAQ & trigger board co-design, board manufacture, racks, Ćmonitoring & controls hardware, some on-line hardware ĆDAQ & trigger board co-design, crates, cables, on-line hardware Ćoff-line hardware & data archiving in US, system test platform Ć

5 DAQ, Trigger, Online & Offline Software Ć ĆOverall software architecture, DAQ & trigger software, shared sharedon-line & off-line software, simulations software shared sharedMonitoring & controls software Ć

6 Conventional Construction & Equipment ĆTunnels, entrances, experimental halls, underground utilities, Ćsafety systems, surface facilities Ć

7 System Integration Ć Ć

8 Project Management Ć Ć

Majority ResponsibilityWBS Description China US

1 Central Detector ĆSystem design, steel vessels, unloaded LS, mineral oil, Ćreadout electronics co-design, electronics mfg, safety Ćsystems, racks, assembly & installation ĆAcrylic vessels, PMT's & support structure, Gd loaded LS, Ć LS purification system, locomotion system, readout Ćelectronics co-design, cables, crates Ć

2 Veto Detector ĆSystem design, muon tracker system, supplemental water Ćveto PMT's, muon tracker assy & test ĆWater veto system hardware, compensation coils, readout Ćelectronics mfg, safety syst, water veto assy & test Ć

3 Calibration & Monitoring Systems ĆAutomated deployment system & glove box, laser sources, Ćmonitoring system & system test ĆManual calibration sys & glovebox, LED sources, radioactive Ćcalib. sources, low-background source & matls counting syst Ć

U.S.-China primary responsibilitiesU.S. Scope

• Russia: liquid scintillator, calibration, and plastic scintillator• Taiwan: acrylic vessels and trigger• Hong Kong: calibration and data storage

other contributions


U.S. Project Scope & Budget

BudgetInstitution WBS element Lead? target ($K) Comments

BNL Muon tracker system Y 5,000 joint with university groupsGd-loaded liquid scintillator Y 1,500 may include LS purification system

California Institute Techology Calibration systems Y 2,000 joint with univ groups & LBNL

University of Houston DAQ hardward & software 1,000 joint with univ groups & LBNL

LBNL Project management Y 1,700System integration Y 1,700 joint with BNLPMT's, bases & control Y 3,000 joint with university groupsLocomotion & cranes Y 600 joint with BNLReadout & trigger electronics 1,000 joint with univ groups & BNLAcrylic Vessels Y 2,000

U. Ill at Urbana-Champaign, addn'l university-based scope 4,200 see next slide for detailsIowa State University,UCLA + other universities

Other Necessary ItemsCommon fund 2,000Project contingency ~30% 7,000

Total:Total: 32,700


Overall Project Schedule


Project Development

• Schedule/activities over next several months:

Determine scale of detector for sizing halls:

Continue building strong U.S. team - key people:

Conceptual design, scale & technology choices:

Firm up U.S. scope, schedule & cost range:

Write CDR, prepare for CD-1:

now – June

now – summer

now – Aug

July – Nov

Aug – Nov


Funding Profile

CD-1 review November 2006

Begin construction in China March 2007

CD-2 review September 2007

Begin data collection January 2010

Measure sin2213 to 0.01 March 2013

FY06 U.S. R&D $2M FY07 $3.5MFY08 U.S. Construction $10MFY09 $14MFY10 $8M


Summary and Prospects

• The Daya Bay nuclear power facility in China and the mountainous topology in the vicinity offer an excellent opportunity for carrying out a measurement of sin2213 at a sensitivity of 0.01.

• The Chinese funding agencies have agreed in principle to a request of RMB 150M to fund civil construction and ~half of the detector.

• NuSAG endorsed U.S. participation in a 13 experiment, P5 is evaluating 13

experiments as part of the Roadmap, and we are hopeful for a positive decision by DOE.

• BNL/LBNL submitted R&D request to DOE for FY06 in January 2006.

• Have begun to form project leadership team with China: progress on organization, scope and cost.

• Will complete a conceptual design of detectors, tunnels and underground facilities in 2006, aiming for CD1 review this year and a CD2 review in 2007.

• In the ~3 months since BNL joined the Daya Bay collaboration we have made huge strides in defining and understanding the project and the U.S. scope.

• Plan to commission a Fast Deployment plan in 2009, with full operation in 2010.


Backup


A Versatile Site

• Rapid deployment:- Daya Bay near site + mid site - 0.7% reactor systematic error

• Full operation: (A) Two near sites + Far site (B) Mid site + Far site (C) Two near sites + Mid site + Far site Internal checks, each with different systematic


~350 m

~97 m

~98 m~208 m

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

DYB LingAo Mid Far

Elevation (m) 97 98 208 347

(m.w.e.) 280 280 560 930

Flux (Hz/m2) 1.2 0.94 0.17 0.045

Mean Energy (GeV) 55 55 97 136

near site

far site


Science Goals → Experiment Design → R&D

Reduce and control systematic errors:

• “Identical” detectors at multiple sites → detector design/construction, side-by-side comparisons

U.S. R&D tasks focused on achieving these goals

• Detector performance - well-understood, stable → materials/construction, calibration/monitoring• Reduce radioactivity background → materials/construction, Gd-loaded scintillator• Reduce and measure cosmogenic backgrounds → shielding, muon veto and tracking, DAQ system• Swap detectors → horizontal tunnel system, locomotion equipment


Background estimated by GEANT MC simulation

Near far

Neutrino signal rate(1/day) 560 80

Natural backgrounds(Hz) 45.3 45.3

Single neutron(1/day) 24 2

Accidental BKG/signal 0.04% 0.02%

Correlated fast neutron Bkg/signal 0.14% 0.08%

8He+9Li BKG/signal 0.5% 0.2%


Detector-related Uncertainties

Baseline: currently achievable relative uncertainty without R&D Goal: expected relative uncertainty after R&D

Absolutemeasurement

Relativemeasurement

→ 0→ 0.006

→ 0.06%

w/Swapping

→ 0

Swapping: can reduce relative uncertainty further


Experimental Parameters


H/C ratio

• CHOOZ claims 0.8% absolute based on multiple lab analyses (combustion)

• We need only relative measurement

• Double-CHOOZ claims 0.2%

Adopt 0.2% baseline Adopt 0.1% goal

R&D: measure via NMR or neutron capture


Target Volume

• KamLAND: ~1%• CHOOZ: 0.02%?

• Flowmeters – 0.02% repeatability

Baseline = 0.2% Goal = 0.02%


Energy Cuts

• CHOOZ = 0.8% absolute• Baseline 0.2%• Goal = 0.05% for

2% energy calibration


Energy Cuts

KamLAND calibration data:


Time Cuts

Neutron time window uncertainty:

t = 10 ns 0.03% uncertainty Use common clock for detector modules

Baseline = 0.1% Goal = 0.03%


H/Gd ratio

CHOOZ measured to ±0.5s =0.01% for t1=0.2s

Measure neutron capture time


Livetime

• Measure relative livetimes using accurate common clock• Should be negligible error (note SNO livetime error of ~10-5


What Have We Learned From Chooz?

CHOOZ Systematic Uncertainties

Reactor flux & spectrumDetector Acceptance

2%1.5%

Total 2.7%

5 t Gd-loaded liquid scintillatorto detect

L = 1.05 km

D = 300 mwe

P = 8.4 GWthRate: ~5 events/day/t (full power) including 0.2-0.4 bkg/day/t

e + p e+ + n

e+ + e- 2 x 0.511 MeV n + Gd 8 MeV of s; ~ 30 s

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


Num

ber o

f Ant

i-neu

trino

s per

0.05

MeV

per

fissio

n0

2

4

6

8

10

0 2 4 6 8 10

Total

Cro

ss S

ectio

n (10

-40

cm2 )

Energy (MeV)

Cross Section

dN/dE

Observed Events (arbitrary scale)

Reactor anti-e

For 235U, for instance, an average of 6 es are produced per fission (~200 MeV).

e/M

eV

/fiss

ion

3 GWth generates 61020 e per sec

P(e e )1

- 42


Time Variation of Fuel Composition

Typically known to ~1%

235U

238U239Pu

241Pun

orm

aliz

ed

flu

x t

imes

cross

sect

ion

(arb

itra

ry u

nit

s)

0

0

.5

1

1.5

2

2.5

3

3

.5

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


Calibration

• Radioactive Source 137Cs, 22Na, 60Co, 54Mn, 65Zn , 68Ge, Am-Be

252Cf, Am-Be

• Gamma generator

p+19F→ α+16O*+6.13MeV; p+11B→ α+8Be*+11.67MeV

• Backgrounds

40K, 208Tl, cosmic-induced neutrons, Michel’s electrons, …

• LED calibration

KI & CIAE

Hong Kong


What Target Mass Should Be?

Systematic errorBlack : 0.6%

DYB: B/S = 0.5% LA: B/S = 0.4% Far: B/S = 0.1%

m231 = 2 10-3 eV2

tonnes

(3 year run)

Red : 0.25% (baseline goal)Blue : 0.12%


Sensitivity

For 3 years

With four 20-t modules at the far site and two 20-t modules at each near site:


Precision of m231

sin2213 = 0.02

sin2213 = 0.1


Synergy of Reactor and Accelerator Experiments

Δm2 = 2.5×10-3 eV2 sin2213 = 0.05

Reactor experiments can help in Resolving the 23 degeneracy

(Example: sin2223 = 0.95 ± 0.01)

90% CL

Reactor w 100t (3 yrs) + Nova Nova only (3yr + 3yr) Reactor w 10t (3yrs) + Nova

90% CL

McConnel & Shaevitz, hep-ex/0409028

90% CL

Reactor w 100t (3 yrs) +T2K T2K (5yr,-only) Reactor w 10t (3 yrs)+T2K

Reactor experiments providea better determination of 13

Documents

The Daya Bay Experiment Steve Kettell BNL 1)Motivation 2)Reactor anti- e 3)Daya Bay Experiment 4)Collaboration/BNL involvement