Measuring sin22q13 with the Daya Bay nuclear power reactorsYifang WangInstitute of High Energy Physics

Neutrinos Basic building blocks of matter

Tiny mass, neutral, almost no interaction with matter, very difficult to detect.Enormous amount in the universe, ~ 100/cm3 , about 0.3% -1% of the total mass of the universeMost of particle and nuclear reactions produce neutrinos: particle and nuclear decays, fission reactors, fusion sun, supernova, g-burstcosmic-rays Important in the weak interactions P violation from left-handed neutrinosImportant to the formation of the large structure of the universe, may explain why there is no anti-matter in the universe

Brief history of neutrinos1930 Pauli postulated neutrinos 1956 Neutrinos discovered1995 Nobel prize1962 -neutrino discovered1988 Nobel prize 1957 Pontecorvo proposed neutrino oscillation1968 solar neutrino deficit, oscillation ? 2002 Nobel prize 1998 atmospheric neutrino anomaly => oscillation (2002 Nobel prize2001 SNO:solar ne conversion => oscillation 2002 KamLAND:reactor ne deficit => oscillation Neutrino oscillation: a way to detect neutrino massA new window for particle physics, astrophysics, and cosmology

Neutrino oscillation: PMNS matrix EXOGeniusCUORENEMOA total of 6 parameters: 2 Dm2, 3 angles, 1 phases+ 2 Majorana phasesIf Mass eigenstates Weak eigenstates Neutrino oscillationOscillation probability P(n1->n2) sin2(1.27Dm2L/E)Atmospheric solar bb decayscrossingCP q13Super-KK2KMinosT2KDaya BayDouble ChoozNOVAHomestakeGallexSNOKamLAND

Evidence of Neutrino Oscillations

Unconfirmed:LSND:Dm2 ~ 0.1-10 eV2

Confirmed:Atmospheric:Dm2 ~ 210-3 eV2Solar:Dm2 ~ 8 10-5 eV2

P(n1->n2) = sin22qsin2(1.27Dm2L/E)2 flavor oscillation in vacuum:

A total of six n mixing parametersat reactors: Pee 1 sin22q13sin2 (1.27Dm213L/E) cos4q13sin22q12sin2 (1.27Dm212L/E)at LBL accelerators: Pme sin2q23sin22q13sin2(1.27Dm223L/E) + cos2q23sin22q12sin2(1.27Dm212L/E) A(r)cos2q13sinq13sin(d)Known |D m232|, sin22q32 --Super-K D m221, sin22q21 --SNO,KamLANDUnknownsin22q13 d, sign of Dm232

Why at reactorsClean signal, no cross talk with d and matter effectsRelatively cheap compare to accelerator based experiments Can be very quickProvides the direction to the future of neutrino physics

Small-amplitudeoscillation due to 13 Large-amplitudeoscillation due to 12

Current Knowledge of 13Global fitfogli etal., hep-ph/0506083Sin2(213) < 0.09Sin2(213) < 0.18Direct search PRD 62, 072002Allowed region

No good reason(symmetry) for sin22q13 =0Even if sin22q13 =0 at tree level, sin22q13 will not vanish at low energies with radiative correctionsTheoretical models predict sin22q13 ~ 0.1-10 %

An experiment with a precision for sin22q13 less than 1% is desiredmodel prediction of sin22q13Experimentally allowedat 3s level

Importance to know q131A fundamental parameter 2important to understand the relation between leptons and quarks, in order to have a grand unified theory beyond the Standard Model

3important to understand matter-antimatter asymmetryIf sin22q13>0.01next generation LBL experiment for CP If sin22q13

Recommendation of APS study report:2004.11.4 APS

How to do this experiment

How Neutrinos are produced in reactors ?

The most likely fissionproducts have a total of 98 protons and 136 neutrons, hence on average there are 6 n which will decay to 6p, producing 6 neutrinosNeutrino flux of a commercial reactor with 3 GWthermal : 6 1020 /s

Fission rate evolution with time in the Reactor Neutrino rate and spectrum depend on the fission isotopes and their fission rate

Neutrino energy spectrumK. Schreckenbach et al., PLB160,325A.A. Hahn, et al., PLB218,365F exp(a+bEn+cEn2)P. Vogel et al., PRD39,3378

Reactor thermal powerFission rate depend on the thermal power

Typically Known to ~ 1%

Prediction of reactor neutrino spectrum Three ways to obtain reactor neutrino spectrum:Direct measurementFirst principle calculationSum up neutrino spectra from 235U, 239Pu, 241Pu and 238U 235U, 239Pu, 241Pu from their measured b spectra 238U(10%) from calculation (10%)They all agree well within 3%

10-40 keVNeutrino energy:Neutrino Event: coincidence in time, space and energy neutrino detection: Inverse- reaction in liquid scintillator1.8 MeV: Threshold t 180 or 28 ms(0.1% Gd)n + p d + g (2.2 MeV)n + Gd Gd* + g (8 MeV)

Reactor Experiment: comparing observed/expected neutrinos:Palo Verde CHOOZKamLANDTypical precision: 3-6%

How to reach 1% precision ?Three main types of errors: reactor related(~2-3%), background related (~1-2%) and detector related(~1-2%)Use far/near detector to cancel reactor errorsMovable detectors, near far, to cancel part of detector systematic errorsOptimize baseline to have best sensitivity and reduce reactor related errorsSufficient shielding to reduce backgroundsComprehensive calibration to reduce detector systematic errorsCareful design of the detector to reduce detector systematic errorsLarge detector to reduce statistical errors

Systematic error comparison

xperiAngra, BrazilDiablo Canyon, USABraidwood, USAChooz, FranceKrasnoyasrk, RussiaKashiwazaki,JapanDaya Bay, ChinaYoung Gwang, South KoreaProposed Reactor Neutrino Experiments

Currently Proposed experiments

Site(proposal)Power(GW)BaselineNear/Far (m)DetectorNear/Far(t)OverburdenNear/Far (MWE)Sensitivity(90%CL)Double Chooz (France)8.7150/106710/1060/300~ 0.03Daya Bay (China)11.6360/500/180040/40/80260/260/910~ 0.008Kaska(Japan)24.3350/16006/6/2 690/90/260~ 0.02Reno(S. Korea)17.3150/150020/20230/675~ 0.03

Daya Bay nuclear power plant4 reactor cores, 11.6 GW2 more cores in 2011, 5.8 GW Mountains near by, easy to construct a lab with enough overburden to shield cosmic-ray backgrounds

Convenient Transportation,Living conditions, communicationsDYB NPP region - Location and surrounding 60 km

Cosmic-muons at sea level: modified Gaisser formula

Cosmic-muons at the laboratory

Baseline optimization and site selection Neutrino spectrum and their errorNeutrino statistical errorReactor residual errorEstimated detector systematical error: total, bin-to-binCosmic-rays induced background (rate and shape) taking into mountain shape: fast neutrons, 9Li, Backgrounds from rocks and PMT glass

Best location for far detectorsRate onlyRate + shape

Total Tunnel length3200 mDetector swapping in a horizontal tunnel cancels most detector systematic error. Residual error ~0.2%BackgroundsB/S of DYB,LA ~0.5%B/S of Far ~0.2%Fast MeasurementDYB+Mid, 2008-2009Sensitivity (1 year) ~0.03Full MeasurementDYB+LA+Far, from 2010Sensitivity (3 year)

Geologic survey completed, including boreholesWeathering bursa (Faults(small)farnearnearmid

Site investigation completed

Engineering Geological Map

Engineering geological sectionsLine A

Tunnel constructionThe tunnel length is about 3000mLocal railway construction company has a lot of experience (similar cross section)Cost estimate by professionals, ~ 3K $/mConstruction time is ~ 15-24 monthsA similar tunnel on site as a reference

How large the detector should be ?

Detector: Multiple modulesMultiple modules for cross check, reduce uncorrelated errors Small modules for easy construction, moving, handing, Small modules for less sensitive to scintillator agingScalableTwo modules at near sitesFour modules at far site:Side-by-side cross checks

Central Detector modulesThree zones modular structure: I. target: Gd-loaded scintillatorII. g-ray catcher: normal scintillator III. Buffer shielding: oil Reflection at two ends20t target mass, ~200 8PMT/module sE = 5%@8MeV, ss ~ 14 cm

IIIIIIg Catcher thicknessOil buffer thickness

IsotopesPurity(ppb)20cm(Hz)25cm (Hz)30cm(Hz)40cm(Hz)238U(>1MeV)502.72.01.40.8232Th(>1MeV)501.20.90.70.440K(>1MeV)101.8 1.30.90.5Total5.74.23.01.7

Water Buffer & VETO2m water buffer to shield backgrounds from neutrons and gs from lab walls Cosmic-muon VETO Requirement: Inefficiency < 0.5%known to 95%Muon tracker, Eff. > 90%RPCscintillator stripstotal ineff. = 10%*5% = 0.5% Neutron background vs water shielding thickness2m water

Two tracker options :RPC outside the steel cylinderScintillator Strips sink into the waterRPC from IHEPScintillator Strips from UkraineContribution of JINR,Dubna

Background related errorNeed enough shielding and an active vetoHow much is enough ? error < 0.2%Uncorrelated backgrounds: U/Th/K/Rn/neutron single gamma rate @ 0.9MeV < 50Hz single neutron rate < 1000/day 2m water + 50 cm oil shieldingCorrelated backgrounds: n Em0.75Neutrons: >100 MWE + 2m water Y.F. Wang et al., PRD64(2001)0013012 8He/9Li: > 250 MWE(near) & >1000 MWE(far) T. Hagner et al., Astroparticle. Phys. 14(2000) 33

Fast neutron spectrumPrecision to determine the 9Li background in situSpectrum of accidental background

Background estimated by GEANT MC simulation

Near farNeutrino signal rate(1/day)56080Natural backgrounds(Hz)45.345.3Single neutron(1/day)242Accidental BK/signal0.04%0.02%Correlated fast neutron Bk/signal 0.14%0.08%8He+9Li BK/signal0.5%0.2%

Sensitivity to Sin22q13Reactor-related correlated error: sc ~ 2% Reactor-related uncorrelated error: sr ~ 1-2%Calculated neutrino spectrum shape error: sshape ~ 2%Detector-related correlated error: sD ~ 1-2%Detector-related uncorrelated error: sd ~ 0.5%Background-related error: fast neutrons: sf ~ 100%, accidentals: sn ~ 100%, isotopes(8Li, 9He, ) : ss ~ 50-60%Bin-to-bin error: sb2b ~ 0.5%Many are cancelled by the near-far scheme and detector swapping

Sensitivity to Sin22q13 Other physics capabilities:Supernova watch, Sterile neutrinos,

Prototype: 45 PMT for 0.6 t LS

Backgrounds 60Co spectrumUniformity before correction linearity s=5.6% @ 2.5 MeVIn agreement with or better than expectation

Development of Gd-loaded LSLS (Gd0.1% Mesitylene 40% 60% bicron mineral oil)IHEP and BNL both developed Gd-loaded LS using LAB: high light yield, high flash point, low toxicity, cheap, long attenuation length

SampleAttenuation Lengths (m)2: 8 mesitylene: dodecaneLS15.0PPO 5g/L bis-MSB 10mg/L in LS11.30.2% Gd-EHA in LS8.30.2% Gd-TMHA in LS7.2LAB~PPO 5g/L bis-MSB 10mg/L in LAB23.70.2% Gd-TMHA PPO 5g/L bis-MSB 10mg/L in LAB19.10.2% Gd-EHA PPO 5g/L bis-MSB 10mg/L in 2: 8 mesitylene: LAB 14.1

Electronics for the prototype Readout moduleReadout Electronics

From PMT

-5V

50

AD9215

+

-

High speedAmp.

AD8132

+

-

RC=50ns

RC=100ns

RC2

10K

10pF

Amp.

DAC

threshold

start

stop

S2D

10pF

50

`

CH2

Disc.

Single ended to diff.

10bit

L1 Trigger (LVPECL)

TDC

Pipeline

charge

40MHz Clock (LVPECL)

time

DATABUFFER

L1

VMEinterface

CLK

CLK

Single channel macro in FPGA

X 16

CLK

200ns width

10bit/40MSPSFlash ADC

FPGA

To VME bus

< 1s width

resol.: 0.5ns

1K

< 300ns width

1K

CH16

CH1

10ns width

+

-

1K

Energy sum to trigger module

AD8065

SUM

integrator

Test input

Aberdeen tunnel in HK:background measurement

North America (9)LBNL, BNL, Caltech, UCLAUniv. of Houston,Univ. of IowaUniv. of Wisconsin, IIT, Univ. of Illinois-Urbana-champagneChina (12)IHEP, CIAE,Tsinghua Univ.Zhongshan Univ.,Nankai Univ.Beijing Normal Univ., Shenzhen Univ., Hong Kong Univ.Chinese Hong Kong Univ.Taiwan Univ., Chiao Tung Univ.,National United univ.

Europe (3)JINR, Dubna, RussiaKurchatov Institute, RussiaCharles university, CzechDaya Bay collaboration

Status of the projectCAS officially approved the projectChinese Atomic Energy Agency and the Daya Bay nuclear power plant are very supportive to the projectFunding agencies in China are supportive, R&D funding in China approved and availableR&D funding from DOE approvedSite survey including bore holes completedR&D started in collaborating institutions, the prototype is operationalProposals to governments under preparation Good collaboration among China, US and other countries

Schedule of the projectSchedule2004-2006 R&D, engineering design, secure funding2007-2008 proposal, construction2009 installation2010 running

SummaryKnowing Sin22q13 to 1% level is crucial for the future of neutrino physics, particularly for the leptonic CP violationReactor experiments to measure Sin22q13 to the desired precision are feasible in the near future Daya Bay NPP is an ideal site for such an experimentA preliminary design is ready, R&D work is going on well, proposal under preparation