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(1)

The Elusive Neutrinos –

neutrino oscillation, mixing and mass hierarchy

Yee Bob Hsiung 熊怡

National Taiwan University

March 4, 2014

@National Taiwan University

(2)

What is Neutrino?

什麼是微中子?

Discovery of neutrino

Reines &

Cowen

1956

(3)

Spin 1/2, nearly massless, neutral particle!

from neutron decay

(4)
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(< 2.2 eV)

(8)
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(11)

The Missing Solar Neutrinos

Some of the ν

e

from the sun

are missing.

(12)

Are Due to Neutrino Oscillation

SNO

ν e missing

but ν e + ν μ + ν τ agree

Theory

(13)
(14)

+ Higgs boson

(15)
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21

(22)
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23

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24

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Kam-Biu Luk LP2011 9

Reactor-based ! 13 Experiments

RENO at Gonggwang, Korea

Daya Bay at Daya Bay, China

Double Chooz at Chooz, France

(27)

27

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28

13

Determining θ 13 With Reactor ν e

Look for disappearance of electron antineutrinos from reactors:

Large-amplitude oscillation due to θ12 Small-amplitude oscillation

due to θ13integrated over E

near detector

detector far

Disappearance probability!

R

Far

R

Near

=

L

Near

L

Far

!

"

# $

% &

2

N

Far

N

Near

!

"

# $

% & ε

Far

ε

Near

!

"

# $

% & 1 − P

Far

1− P

Near

!

"

# $

% &

νe rate 1/r2

number of protons

detection

efficiency yield sin213#

Perform a relative measurement:

sin213 = 0.1

All correlated errors cancelled.

Yee Bob Hsiung

(29)

29

12

Knowledge of θ 13 before 2012

PRL107,041801 (2011) PRL107, 181802 (2011)

arXiv:1112.6353

= 0.944±0.016±0.040 N

obs

N

pre

sin

2

13

= 0.086±0.041±0.030

Double Chooz

T2K MINOS

Far-detector only

Some hints of a non-zero θ

13

1.7 σ#

2.5 σ over bkg 1.7 σ over bkg

Yee Bob Hsiung

(30)

30

(31)

Kam-Biu Luk LP2011 10

The Daya Bay Collaboration

Europe (3) (10)

JINR, Dubna, Russia Kurchatov Institute, Russia Charles University, Czech Republic

North America (16)(~100)

BNL, Caltech, LBNL, Iowa State Univ., Illinois Inst. Tech., Princeton, RPI, Siena,

UC-Berkeley, UCLA, Univ. of Cincinnati, Univ. of Houston,

Univ. of Wisconsin-Madison, Virginia Tech., Univ. of Illinois-Urbana-Champaign

Asia (19) (~140)

IHEP, Beijing Normal Univ., Chengdu Univ.

of Sci. and Tech., CGNPG, CIAE, Dongguan Polytech. Univ., Nanjing Univ., Nankai Univ.,

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

台大, 交大 and 聯合 from Taiwan

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香港大學

Daya Bay Collaboration Meeting in CUHK

(33)

Kam-Biu Luk LP2011 11

Daya Bay Nuclear Power Complex

Daya Bay NPP

Ling Ao NPP Ling Ao II NPP

6 ! 2.95 GW

th

= 17.7 GW

th

• ~55 km from Hong Kong central

• All 6 reactors are in commercial operation

• one of top 5 most powerful nuclear

power plants in the world

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34

(35)

Kam-Biu Luk LP2011 12

Daya Bay reactors

Ling Ao reactors

Ling Ao II reactors

Daya Bay near

Ling Ao near

Water Hall

Far

Hall LS

Entrance

Construction tunnel

Target mass: 20t ! 4 Overburden: ~910mwe Event rate: (~90/day) ! 4 Muon rate: 0.04 Hz/m2

B/S: ~0.2% Target mass: 20t ! 2

Overburden: ~300mwe Event rate: (~740/day) ! 2 Muon rate: 0.73 Hz/m2 B/S: ~0.4%

Target mass: 20t ! 2 Overburden: ~270 mwe Event rate: (~840/day) ! 2 Muon rate: 1.2 Hz/m2 B/S: ~0.4%

Tunnel

Control Building

Surface Assembly Building (SAB)

m

(36)

17

Daya Bay Detector Design

3m acrylic Vessel 192 PMTs

4m acrylic tank sandwiched between top and bottom reflectors Stainless steel

Tank

20t Gd-LS (target)

20t liquid scint.

(gamma catcher) 37t mineral

oil shield

5m 5m

Calibration units (LED, 68Ge,

AmC-Co)

Four layers of RPC’s to tag muons

2.5m water:

-

attenuates gamma rays & neutrons

- forms two optically decoupled Cherenkov counters

Inner Cherenkov

Outer Cherenkov

Yee Bob Hsiung

(37)

20

Detecting Reactor ν e

ν

e

e

+

γ

γ γ γ γ n

•  Use the inverse

β

-decay reaction in Gd-doped liquid scintillator:

ν

e

+ p → e

+

+ n (prompt signal)

→ + p → D + γ (2.2 MeV) (delayed signal)

→  + Gd → Gd*

→ Gd + γ’s (8 MeV) (delayed signal)

~180µs

~30µs

for 0.1% Gd

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

•  Energy of ν

e

is given by:

E

ν

≈ T

e+

+ T

n

+ (m

n

- m

p

) + m

e+

≈ T

e+

+ 1.8 MeV

10-40 keV

Yee Bob Hsiung

(38)
(39)

Interior of Antineutrino Detector

Yee Bob Hsiung 18

(40)

3m IAVs produced in Taiwan

•  All 3m inner acrylic vessels are produced in Taiwan

•  10mm thick wall, 15mm top /bottom covers

•  Completely sealed with two penetration ports for Gd-LS filling and calibations.

•  UV transparent down to 300nm wavelength

Yee Bob Hsiung 19

(41)

Calibration System of Antineutrino Detectors

R=1.7725 m R=0 R=1.35m

3 sources for each z axis on a turntable (position accuracy < 5 mm):

•  10 Hz

68

Ge (2×0.511 MeV γ’s)

•  0.5 Hz

241

Am-

13

C neutron source (3.5 MeV n without γ) + 100 Hz

60

Co gamma source (1.173+1.332 MeV γ)

•  LED diffuser ball (500 Hz) for PMT gain and timing

Three axes: center, edge of target, middle of gamma

catcher

21

3 Automatic calibration ‘robots’ (ACUs) on each detector

ACU-A ACU-B ACU-C

Yee Bob Hsiung

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Stainless Steel Vessel (SSV) in assembly pit

Install Acrylic Vessels Install lower reflector

Install PMT ladders

Install top reflector

Close SSV lid

Install calibration units

22

Assemble Antineutrino Detectors

Yee Bob Hsiung

(43)

23

Liquid Scintillators

•  Gd (0.1%) + PPO (3 g/L) + bis-MSB (15 mg/L) + LAB

•  Number of proton:

(7.169±0034) × 10

25

p per kg

•  185-ton Gd-LS + 196-ton LS production

185-t 0.1% Gd-LS stored in five 40-t tanks

A 1-m apparatus yielded attenuation length of ~15 m @ 430 nm.

Yee Bob Hsiung

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24

Fill Antineutrino Detectors (ADs)

•  Target mass is measured with:

(1) 4 load cells supporting the 20-t ISO tank

(2) Coriolis mass flow meters Absolute uncertainty: 0.02%

Relative uncertainty: 0.02%

•  Temperature is maintained constant

•  Filling is monitored with in-situ sensors

ISO tank

Coriolis mass flow meters

Fill ADs with liquids

underground

Move AD into tunnel

Yee Bob Hsiung

(45)

Yee Bob Hsiung 25

Daya Bay Near Hall (EH1)

Install filled AD in pool Fill pool with purified water

Place cover over pool Roll RPC over cover

Data taking started on 15 Aug 2011

(46)

Getting Ling Ao Near and Far Halls Ready

26

EH 2 (Ling Ao Near Hall):

Began operation on 5 Nov 2011

EH 3 (Far Hall):

Started data-taking on 24 Dec 2011

Yee Bob Hsiung

(47)

Triggers & Their Performance

Yee Bob Hsiung 28

Discriminator threshold:

- ~0.25 p.e . for PMT signal

Triggers:

- AD: ≥ 45 PMTs (digital trigger) ≥ 0.4 MeV (analog trigger)

- Inner Water Cherenkov: ≥ 6 PMTs

- Outer Water Cherenkov: ≥ 7 PMTs (near) ≥ 8 PMTs (far) - RPC: 3/4 layers in each module

Trigger rate:

- AD: < 280 Hz

- Inner Water Cherenkov: < 160 Hz

- Outer Water Cherenkov: < 200 Hz

(48)

Energy Calibration

Yee Bob Hsiung 30

Gain vs. time

60

Co at center

Energy vs. position

Light yield: ~163 p.e./MeV

(49)

Selecting Antineutrino (IBD) Candidates

Yee Bob Hsiung 32

Use Prompt + Delayed correlated signal to select antineutrino candidates.

Selection:

-

Prompt: 0.7 MeV < E

p

< 12 MeV -

Delayed: 6.0 MeV < E

d

< 12 MeV -

Capture time: 1 μ s < Δ t < 200 μ s -

Reject Flashers

- Muon Veto:

Pool Muon: Reject 0.6ms

AD Muon (>20 MeV): Reject 1ms

AD Shower Muon (>2.5GeV): Reject 1s - Multiplicity:

No other signal > 0.7 MeV

in -200 μs to 200 μs of IBD.

From Bemporad, Gratta and Vogel

Arbitrary

Flux Cross Section νe spectrum

(no oscillation)

(50)

Yee Bob Hsiung 33

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Yee Bob Hsiung 36

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52

PRL 112, 061801 (2014)

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JUNO

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JUNO

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Thank You

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