Daya Bay Experiment and

the Future of

Chinese Neutrino Physics Program

Yifang Wang

Institute of High Energy Physics

Oxford, March 4, 2014

Supernova

Sun

Earth Reactor

Galaxy

Big Bang

Accelerator

Human body

Neutrinos around us

Astrophysics

Cosmology

Nuclear physics

Geology

Particle physics

2014-3-7 2

Neutrinos Fundamental building blocks of matter:

Abundant: 300/cm3 in the Universe, same as photons

Mass: the central issue of neutrino physics Although tiny, very important to the universe

Not massless: Only evidence beyond the Standard Model of

particle physics

Neutrinos and cosmology

Part of dark matter

Related to matter-antimatter asymmetry

Related to the universe evolution, large scale structure, …

e

e

bsd

tcu

2014-3-7 3

Neutrinos are useful Neutrino astronomy

Proved the solar model

Supernovae study

Neutrinos from deep Universe

Cosmic-rays

Neutrino geology

Earth thermal emission

U/Th ratio in earth

Neutrino beams through earth: CT ?

Rector monitoring

2014-3-7 4

Neutrino Oscillation If the neutrino mass eigenstate is different from that of the

weak interaction, neutrinos can oscillate: from one type to

another during the flight:

e e

Oscillation

probability：

P(e->) = sin2(2q) sin2(1.27Dm2L/E)

Oscillation

amplitude

Oscillation

frequency

Oscillation matrix

for 3 generations：

Known parameters： q23，q12，DM223， DM2

12，

Recent progress: q13

Unknown parameters: mass hierarchy(DM223), CP phase d

2014-3-7 5

Daya Bay: for a New Type of Oscillation

1

2

3

q12 Solar

Oscillation

q23 Atm.

Oscillation

q13 ?

Fundamental principles

Fundamental parameter

Direction of future neutrino

physics:

If q13 is too small，CPV cannot

be figured out in the near future

CPV can be measured by

Pe ≈ sin2q23sin22q13sin2(1.27Dm223L/E)

+ cos2q23sin22q12sin2(1.27Dm212L/E)

- A(r)cos2q13sinq13sin(d)

2014-3-7 6

Direct Searches in the Past

Palo Verde & Chooz: no signal

T2K: 2.5 s over bkg（2011）

Minos: 1.7 s over bkg（2011）

Double Chooz: 1.7 s（2011）

Allowed region

Sin22q13 < 0.15 @ 90%C.L.

if DM223 = 0.0024 eV2

0 < Sin22q13 < 0.12 @ 90%C.L. NH

0 < Sin22q13 < 0.19 @ 90%C.L. IH

sin22θ13=0.086±0.041(stat)±0.030(sys)

0.03 < Sin22q13 < 0.28 @ 90%C.L. for NH

0.04 < Sin22q13 < 0.34 @ 90%C.L. for IH

2014-3-7 7

Sin22q13 prediction

Experiments with neutrinos from reactors

Huge production yield：6 1020 /s @ 3 GW

Powerful background

rejection capability：

2014-3-7 8

nepe

10-40 keV

Neutrino energy:

-epnne

mMMTTE )(

1.8 MeV: Threshold

Reactor Experiments: comparing

observed/expected neutrinos

Precision of past experiments，typically 3-6%

Reactor power: ~ 1%

Spectrum: ~ 0.3%

Fission rate: 2%

Backgrounds: ~1-3%

Target mass: ~1-2%

Efficiency: ~ 2-3%

Our design goal：a precision of ~ 0.4% 2014-3-7 9

Pee 1 - sin22q13sin2 (1.27Dm213L/E) -

cos4q13sin22q12sin2 (1.27Dm212L/E)

Daya Bay Experiment: Layout

Relative measurement to cancel Corr. Syst. Err. 2 near sites, 1 far site

Multiple AD modules at each site to reduce Uncorr. Syst. Err.

Far: 4 modules，near: 2 modules

Multiple muon detectors to reduce veto eff. uncertainties

Water Cherenkov： 2 layers

RPC： 4 layers at the top + telescopes 2014-3-7 10

Redundancy !!!

Cross check; Reduce errors by 1/N

Comparison with others

• Higher luminosity

Faster to accumulate statistics

• Smaller systematics (in fact 0.2%√N)

Higher precision

• More overburden

Less backgrounds

Experiment Luminosity

(t GW) Detector

uncertainty Overburden

(Near/far)(MWE) Sensitivity (90%CL)

Daya Bay 1400 0.38%/√N 250 / 860 ~ 0.008

Double Chooz 70 0.6% 120 / 300 ~ 0.03

RENO 260 0.5% 120 / 450 ~ 0.02

Huber et al. JHEP 0911:044, 2009

Daya Bay

Double Chooz

Reno

11 2014-3-7

The Daya Bay Collaboration

Europe (2)

JINR, Dubna, Russia

Charles University, Czech Republic

North America (16)

BNL, Caltech, LBNL, Iowa State Univ.,

Illinois Inst. Tech., Princeton, RPI,

UC-Berkeley, UCLA, Univ. of Cincinnati,

Univ. of Houston, Univ. of Wisconsin,

William & Mary, Virginia Tech.,

Univ. of Illinois-Urbana-Champaign, Siena

Asia (20)

IHEP, Beijing Normal Univ., Chengdu Univ.

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

Polytech. Univ., Nanjing Univ., Nankai Univ.,

NCEPU, Shandong Univ., Shanghai Jiao tong

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. ~250 Collaborators

2014-3-7 12

Aug. 2003: Experimental plan and the detector design is proposed

2006: Project approved in China, and afterwards in other countries

Oct. 2007: Civil construction started

Dec.2010: All the blasting for the tunnel and underground hall completed

2008-2011: Detector construction, assembly and installation

Aug. 2011: Near detector data taking started

Dec. 2011: Far detector data taking started full detector data taking

Timeline of the Experiment

13

Opening ceremony：Oct. 2007 2014-3-7

Tunnel and Underground Lab

•Tunnel: ~ 3100m

•3 Exp. hall

•1 hall for LS

•1 hall for water

A total of ~ 3000

blasting right next

reactors. No one

exceeds safety limit

set by National

Nuclear Safety

Agency（0.007g）

14 2014-3-7

Anti-neutrino Detector (AD)

Target: 20 t, 1.6m

g-catcher: 20t, 45cm

Buffer: 40t, 45cm

Total weight: ~110 t

Three zones modular structure: I. target: Gd-loaded scintillator

II. g-catcher: normal scintillator

III. buffer shielding: oil

192 8” PMTs/module

Two optical reflectors at the top

and the bottom, Photocathode

coverage increased from 5.6% to 12%

2014-3-7 15

~ 163 PE/MeV

Detector Assembly

SSV 4m AV

PMT

SSV lid ACU

Bottom reflector

Top reflector 3m AV

Leak check 2014-3-7 16

Challenge: Gd-loaded Liquid Scintillator

Liquid production, QA, storage

and filling at Hall 5

185t Gd-LS, ~180t LS, ~320t oil

LAB+Gd (TMHA)3+PPO+BisMSB

Stable over time

Light yield: ~163 PE/MeV

Stable Liquid

Liquid hall：LS production and filling

2014-3-7 17

Water Cerenkov Detector Installation

PMT frame & Tyvek Completed pool PermaFlex painting

Cover Install AD Pool with water

2014-3-7 18

Hall 1(two ADs) Started Operation on Aug. 15, 2011

19 2014-3-7

One AD insalled in Hall 2

Physics Data Taking Started on Nov.5, 2011

2014-3-7 20

Three ADs installed in Hall 3

Physics Data Taking Started on Dec.24, 2011

2014-3-7 21

Daya Bay：Data taking & analysis status

2014-3-7 22

Two detector comparison [1202.6181] • 90 days of data, Daya Bay near only • NIM A 685 (2012), 78-97

First oscillation analysis [1203:1669]

• 55 days of data, 6 ADs near+far • PRL 108 (2012), 171803

Improved oscillation analysis [1210.6327]

• 139 days of data, 6 ADs near+far • CP C 37 (2013), 011001

Spectral Analysis

• 217 days complete 6 AD period • 55% more statistics than CPC result • Reported at NuFACT’2013, paper

submitted

arXiv:1310.6732

Event Signature and Backgrounds

Signature:

Prompt: e+, 1-10 MeV,

Delayed: n, 2.2 MeV@H, 8 MeV @ Gd

Capture time: 28 s in 0.1% Gd-LS

Backgrounds

Uncorrelated: random coincidence of gg, gn or nn

g from U/Th/K/Rn/Co… in LS, SS, PMT, Rock, …

n from a-n, -capture, -spallation in LS, water & rock

Correlated:

Fast neutrons: promptn scattering, delayed n capture

8He/9Li: prompt b decay, delayed n capture

Am-C source: prompt g rays, delayed n capture

a-n: 13C(α,n)16O

nepe

2014-3-7 23

Neutrino Event Selection Pre-selection

Reject Flashers

Reject Triggers within (-2 μs, 200 μs) to a tagged water pool muon

Neutrino event selection

Multiplicity cut

Prompt-delayed pairs within a time interval of 200 μs

No triggers(E > 0.7MeV) before the prompt signal and after the

delayed signal by 200 μs

Muon veto

1s after an AD shower muon

1ms after an AD muon

0.6ms after an WP muon

0.7MeV < Eprompt < 12.0MeV

6.0MeV < Edelayed < 12.0MeV

1μs < Δte+-n < 200μs

2014-3-7 24

Signal+Backgound Spectrum

EH1

138835 signal

candidates

28909 signal

candidates

EH3 B/S @EH1/2 B/S @EH3

Accidentals ~1.4% ~4.5%

Fast neutrons ~0.1% ~0.06%

8He/9Li ~0.4% ~0.2%

Am-C ~0.03% ~0.3%

a-n ~0.01% ~0.04%

Sum ~2% ~5%

2014-3-7 25

66473 signal

candidates

Daily Neutrino Rate Three halls taking data synchronously allows near-far

cancellation of reactor related uncertainties

Rate changes reflect the reactor on/off.

2014-3-7 26

Predictions are absolute,

multiplied by a

normalization factor from

the fitting

Prediction: Baseline（ 3.5cm，

~0.002%）

Target mass（3kg，0.015%）

Reactor neutrino flux

The Most Precise Neutrino Experiment

2014-3-7 27

Design：(0.18 - 0.38) %

Side-by-side Comparison

Expectation:

R(AD1/AD2) = 0.981

Measurement:

0.984 0.004(stat)

0.002(syst)

A New Type of Oscillation Discovered

28 2014-3-7

Observation of electron anti-neutrino disappearance:

R = 0.940 ±0.011 (stat) ±0.004 (syst)

Sin22q13 = 0.092 0.016(stat) 0.005(syst)

c2/NDF = 4.26/4, 5.2 σ for non-zero θ13

F.P. An et al., NIM. A 685(2012)78

F.P. An et al., Phys. Rev. Lett. 108,

(2012) 171803

announced on

Mar. 8, 2012

Energy Response Model

Mapping the true energy Etrue to the reconstructed kinetic energy Erec:

Build models taking into account:

Electronics non-linearity: time-

dependent charge collection

efficiency

Scintillator non-linearity: Quench

effect & Cerenkov radiation

Complicated e+,e-, g’s interactions

in LS， from simulation

Constraint parameters by a fit to all

calibration data

Model difference systematic errors

arXiv:1310.6732 2014-3-7 29

Prompt IBD spectra (~E)

2014-3-7 30

Pure Spectral Analysis

31

θ13 = 0 can be excluded at > 3σ from spectral information alone

2014-3-7

Rate+Spectra Oscillation Results

2014-3-7 32

arXiv:1310.6732

Global Comparison of θ13 Measurements

2014-3-7 33

The three reactor experiments will work together to report results in

a coherent way, and probably can report a combined result.

Be careful to take the average:

Correlated errors

Error estimate

Current status and future plan

Summer(2012) maintenance

completed Two new AD modules installed

Special Automatic & Manual

calibration completed

Data taking resumed in Oct.

Precision results in three

years, D(sin22q13) ~ 4%

2014-3-7 34

Still a lot of unknowns

Neutrino oscillation：

Neutrino mass hierarchy ?

Unitarity of neutrino mixing matrix ？

Θ23 is maximized ?

CP violation in the neutrino mixing matrix as in the case of

quarks ? Large enough for the matter-antimatter asymmetry in

the Universe ?

What is the absolute neutrino mass ?

Neutrinos are Dirac or Majorana ?

Are there sterile neutrinos？

Do neutrinos have magnetic moments ？

Can we detect relic neutrinos ?

……

2014-3-7 35

Next Experiment: JUNO

Daya Bay Huizhou Lufeng Yangjiang Taishan

Status Operational Planned Planned Under construction Under construction

Power 17.4 GW 17.4 GW 17.4 GW 17.4 GW 18.4 GW

36

Daya Bay

Huizhou Lufeng

Site 2

Site 1

Yangjiang

Taishan

Overburden ~ 700 m Daya Bay JUNO

Talk by Y.F. Wang at ICFA seminar 2008, Neutel

2011; by J. Cao at Nutel 2009, NuTurn 2012 ;

Paper by L. Zhan, Y.F. Wang, J. Cao, L.J. Wen,

PRD78:111103,2008; PRD79:073007,2009 2014-3-7

– LS volume: 20 for more mass & statistics

– light(PE) 5 for resolution

The plan: a large LS detector

20 kt LS

Acrylic tank：F34.5m

Stainless Steel tank ：F37.5m

Muon detector

Water seal

~15000 20” PMTs

coverage: ~80%

Steel Tank

6kt MO

20kt water

1500 20” VETO PMTs 2014-3-7 37

Physics Reach

2014-3-7 38

Thanks to a large θ13

Current Daya Bay II

Dm212 3% 0.6%

Dm223 5% 0.6%

sin2q12 5% 0.7%

sin2q23 5% N/A

sin2q13 14% 4% ~ 15%

• Mass hierarchy

• Precision measurement of

mixing parameters

• Supernova neutrinos

• Geoneutrinos

• Sterile neutrinos

• ……

For 6 years，mass hierarchy cab

be determined at 4s level, if Δm2

can be determined at 1% level

Detector size: 20kt

Energy resolution: 3%/E

Thermal power: 36 GW

Y.F. Li et al., arXiv:1303.6733

Detector design LS detector in the water pool: No Gd-loading

Estimated signal event rate: 40/day

Backgrounds: Accidentals(~10%), 9Li/8He(<1%), fast neutros(<1%)

Several detector options: Acrylic ball + unistruct for PMT

Steel ball + acrylic blocks

Steel ball + acrylic walls + Balloon

…

R&D one the way

Design choice by 2014

Prototype will be started soon

2014-3-7 39

Liquid Scintillator

Longer attenuation length: 15m

30m Improve raw materials (using Dodecane

instead of MO for LAB production）

Improve the production process

Purification

Higher light yield fluor concentration optimization

Linear Alky

Benzene

Atte. L(m) @

430 nm

RAW 14.2

Vacuum

distillation

19.5

SiO2 coloum 18.6

Al2O3 coloum 22.3

LAB from Nanjing,

Raw

20

Al2O3 coloum, fourth

time

27

Al2O3 coloum,

second time

25

Al2O3 coloum, 8th

time

24

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,70,0

0,2

0,4

0,6

0,8

1,0

LIg

ht

ou

tpu

t, r

ela

tive

un

its

PPO mass fraction, %

KamLAND

2014-3-7 40

High QE MCP-PMT Prototypes

underway

SPE

QE

2014-3-7 41

Test results of a prototype

2014-3-7 42

Site selection • Site is determined, configuration is finalized

– A vertical shaft(600 m) + sloped tunnel(1300m)

• Overburden: ~ 700 m

2014-3-7 43

Status of the project

Conceptual design & R&D plan

approved in China

Site determined, geological survey

completed Rock: High quality granite

No water leak

Rock Tem. ~ 31 oC

Detailed civil design underway Bidding process started

Winner(for design and construction)

will be determined on April 1

Paper work to get construction

permission underway

Collaboration will be established

soon

2014-3-7 44

Brief schedule

Civil preparation：2013-2014

Civil construction：2015-2017

Detector R&D：2013-2016

Detector component production：2016-2017

PMT production：2016-2019

Detector assembly & installation：2018-2019

Filling & data taking：2020

2014-3-7 45

After a number of reviews, we are approved by the

CAS(~ CD1)

R&D funding is available

A New Type of Neutrino Beam for CP (MOMENT)

Detector

Neutrinos after the target/ collection/decay: 〉1021 /year

Detector： Flavor sensitive Charge sensitive NC/CC sensitive

46 2014-3-7

Comparison Factory Super pi beam MOMENT

Neutrino energy 2-4 GeV 0.3-0.7，2-4 GeV 300 MeV

Neutrino source Muon decay Pi decay Muon decay

Beam backgrounds no high low

Neutrino flux 1021/year 1018-21/year 51021/year

Proton driver Pulsed 8-16 GeV 4 MW

Pulsed 5-400 GeV 1-5 MW

CW 1.5 GeV 15 MW

Target Mercury Mercury ?

Collection Horn Horn SC magnet

Decay pipe Storage ring Vacuum pipe SC magnet

cooling yes No No

Muon acceleration yes No No

cost High low low

47 2014-3-7

Best energy for CP ? • Below in-elastic threshold: ~ 300 MeV baseline = 150 km • Such a threshold is similar for CC/NC & /bar • Although we loose statistics due to the lower cross section,

but we have less systematics by being p0 free

J.Formaggio and G.Zeller, Rev. Mod.Phys. 84.3(2012)1307

2014-3-7 48

Summary

• Neutrino physics is very promising in the next decades

• Daya Bay experiment is the start of neutrino physics in China

• JUNO will bring us to a new stage

• MOMENT is still under study. Hopefully it can be developed into a real project

• We are looking for collaborators

2014-3-7 49