Reactor Neutrino Experiments - Miami

Reactor Neutrino Experiments

Ke Han Yale University

December 21, 2014

20kt LS (undoped)

Acrylic tank: Φ34.5mStainless Steel tank: Φ37.5m

Reactor Neutrino – A tool for discovery

θ

Miami 2014 Ke Han, Yale University 2

Fireball

Vacuumpump

Feathers andfoam rubber

Vacuumline

Vacuumtank

Suspendeddetector

Back fill

Buried signal linefor triggering release

Nuclear explosive

40 m

30 m

Miami 2014 3 Ke Han, Yale University

“El Monstro” – First design to detect (anti) neutrinos

Suspendeddetector

n → p+ e− + ν̄e

ν̄e + p → e++n

•  Reactor anti-νe Inverse beta decay + neutron capture

Neutrino Discovery by Reines and Cowan in 1956

Hanford, WA, 1953, 300 L Savannah River, SC, 1956, ~5000 L

At the time Cowan and I got into the act, a “big” detector was only a liter or so in volume – Reines, 1995

νeνe

Incidentantineutrino

Positronannihilation

Inverse beta

decay

Gamma rays

Gamma rays

e+

n

Neutron capture

Liquid scintillator and cadmium

ν̄e + p → e++n


Reactor antineutrino


Neutrino Oscillation -- two flavor scenario

| ( )〉 = − cos | 〉+ − sin | 〉

L or t

→ ( ) = − sin sin

( )Survival Probability:

1 5 10 50 100 500

0.0

0.2

0.4

0.6

0.8

1.0

Distance [km]

Surv

ival

Pro

babi

lity

LE

� 1Δm2

LE

� 1Δm2

LE

≈ 1Δm2

sin2(2θ0) = 0.84Eν = 5MeV

Δm2 ≈ 7×10−5eV2• • 

• 


•  1 kton liquid scintillator detector to measure reactor anti-νe disappearance.

•  Confirmed the deficits expected from ν oscillation

•  Observed the periodic feature of the anti-νe survival probability

KamLAND – reactor neutrino disappearance


•  1 kton liquid scintillator detector to measure reactor anti-νe disappearance.

•  Confirmed the deficits expected from ν oscillation

•  Observed the periodic feature of the anti-νe survival probability

KamLAND -- oscillation

(km/MeV)eν

/E0L

20 30 40 50 60 70 80 90 100 110

Surv

ival

Pro

babi

lity

0

0.2

0.4

0.6

0.8

1

eνData - BG - Geo best-fit oscillationν3-

best-fit oscillationν2-


Neutrino mixing – 3 flavor

Short Baseline Reactor LBL Accelerator

⎛⎝ νe

νμντ

⎞⎠=

⎛⎝−

⎞⎠⎛⎝

−

− −

⎞⎠⎛⎝

−

⎞⎠

ci j = cos(i j), si j = sin(i j)

⎛⎝ ν1

ν2ν3

⎞⎠

oscillation frequency L/E →Δm2

ampl

itude

of

osci

llatio

n θ

Δm223 = ~2.4 x 10-3 eV2

Δm212 =~7.6 x 10-5 eV2

Pee ≈1− sin2 2θ13 sin

2 Δm312L

4Eν

⎛

⎝ ⎜

⎞

⎠ ⎟ − cos4 θ13 sin

2 2θ12 sin2 Δm21

2L

4Eν

⎛

⎝ ⎜

⎞

⎠ ⎟


Measuring θ13 with Reactor Experiments

far

νe

distance L ~ 1.5 km

νe,x νe,x

Absolute Reactor FluxLargest uncertainty in previous measurements

Relative MeasurementRemoves absolute uncertainties!

θ13

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

0.1 1 10 100

N osc/N

no_o

sc

Baseline (km)

Δm213≈ Δm2

23

detector 1 detector 2

Near vs Far Detector

near

far/near νe ratio target mass distances efficiency oscillation deficit

νeνe νe


Daya Bay – Observation of anti-ve Disappearance N

dete

cted

/Nex

pect

ed

Based on 55 days of data with 6 ADs, discovered disappearance of reactor νe at short baseline. [PRL 108, 171803]

Obtained the most precise value of θ13:

sin22θ13 = 0.089 ± 0.010 ± 0.005 [CPC 37, 011001]

sin22θ13 > 0

• • • 


RENO

RENO and Double Chooz

2 4 6 8 10 12Energy (MeV)

Even

ts/0.

5 MeV

0102030

2 4 6 8 10 12Energy (MeV)

−100

−50

050

0.60.8

11.21.4

200

400

600

800

1000

1200

1400

Even

ts/0.

5 MeV

(Data/

pred

icted)

(Data/

pred

icted)

(0.5

MeV

)

0

500

1000

Far detectorNear detector

Prompt energy (MeV)

00

10

5 10

Prompt energy (MeV)0 5 10

20

30

40

Entries/

0.25

MeV

Entries/

0.25

MeV

Fast neutronAccidental9Li/8He

Double Chooz


A Precision Measurement of θ13

2011

2013

2012


Reactor Neutrinos – Next Steps

Daya Bay

Double Chooz

RENO

KamLAND

Is the 3-ν picture complete? Are there more than 3 neutrinos?

What is the flux of reactor antineutrinos?

What is the mass hierarchy?

• 

• 

• • 


Oscillation parameter precision measurement

Proposed Projects: JUNO and RENO-50

RENO-50 JUNO


Mass Hierarchy

JUNO


m2

0

solar~7.6×10–5eV2

atmospheric~2.5×10–3eV2

atmospheric~2.5×10–3eV2

m12

m22

m32

m2

0

m22

m12

m32

νe

νμ ντ

? ?

solar~7.6×10–5eV2

Mass Hierarchy Sensitivity

JUNO

•  Reactor antineutrino anomaly: deficit in the observed reactor flux

•  Among other hints of sterile neutrino(s): –  LSND –  MiniBoone –  Gallium –  Neff in cosmology

Reactor neutrino – very short baseline ~10 m

Distance to reactor (m)Bu

gey-

4 ROV

NO

91

Buge

y-3

Buge

y-3

Buge

y-3

Goe

sgen

-I

Goe

sgen

-II

Goe

sgen

-III

ILL

Kras

noya

rsk-

I

Kras

noya

rsk-

II

Kras

noya

rsk-

III

SRP-

ISR

P-II

ROV

NO

88-1

IRO

VN

O88

-2I

ROV

NO

88-1

S

ROV

NO

88-2

S

ROV

NO

88-3

S

Palo

Ver

de

CHO

OZ

Dou

ble C

HO

OZ

0.750.8

0.850.9

0.951

1.051.1

1.15

𝑁O

BS/(

𝑁ex

p) p

red,

new

100 103


•  Spectral deviation of data vs. prediction in 4-6 MeV

•  Recent ab-initio calculation provides a possible explanation involving decays from prominent fission daughter isotopes. Dwyer, Langford: arXiv:1407.1281

Reactor neutrino – very short baseline ~10 m

41.4/24

0.015


Vey short baseline reactor neutrino programs world-wide

μ


PROSPECT- A Precision Reactor Oscillation and Spectrum Experiment

• 

• • 

• 

• • 

• 


U.S. High Power Research Reactor Facilities

Site Power Duty Cycle

Near Baseline

Average Near Flux

Far Baseline

Average Far Flux

NIST 20 MWth 68% 5.3m 1 17.0m 1

HFIR 85 MWth 41% 7.9m 1.1 17.9m 2.3

ATR 110 MWth 68% 10.1m 1.5 18.8m 4.5

Rel

ativ

e Po

wer

(ar

b.)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

x (m)-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6

y (m

)

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6(a)

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

Rel

ativ

e Po

wer

(ar

b.)

0.0

0.2

0.4

0.6

0.8

1.0(e)

Rel

ativ

e Po

wer

(ar

b.)

0.0

0.2

0.4

0.6

0.8

1.0

x (m)-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6

y (m

)

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6(c)

• • 

• • 


PROSPECT Phase I Detector Concept


Detector Development– Segmentation Concept

•  2D segmentation provides 3D position resolution, reasonable channel count, and space efficiency

•  Need for minimal dead material guides design –  Goal: < 2% dead material (>15% for Bugey3)

•  “Unit cell” built from reflecting separators and longitudinal posts – allows excellent calibration access

•  Sealed PMT modules couple via acrylic light guides

~14cm

~100cm

Li-doped LS

Light Guide


Detector Development – Separators and LS

  Li-loaded Scintillator: •  Formulation methods identified

•  Several candidates with good scintillation light yield, capture timing, PSD, compatibility

  Reflecting segment system •  Fabrication method identified

•  Testing multiple material options


•  6Li-capture and Pulse Shape Discrimination •  Strong rejection of accidental and

correlated neutron backgrounds

6Li(n,t)α252Cf

n

γ

LiLS

PS

D P

aram

eter

n Li

n Li iiiiiiiiiiiiiiiiiiiiiiiiiLLiiiiiiiiiiiiiiiiiLLLLLLLLLLLiiiiiiiiiLLLLLLLLLLLi+ γ γ γ +++++++++++++++++++++++++++++++++++++++ γ

n Li n

νe p e+

Del

ay P

SD

γ-γ

Prompt PSD

γ

  Using simulation/deployment data to understand and mitigate electromagnetic-neutron capture correlated backgrounds

Background Rejection & Signal Selection


PROSPECT progression

26

γ

Miami 2014 Ke Han, Yale University

PROSPECT2 operating @ HFIR g

~2 liter Li-LS detector in small B-poly/ lead shield

- not representative of final shield design but useful for MC validation

Studies Underway: •  Muon correlations •  Detailed simulation

comparison •  Internal background

contribution (Rx off) • 


PROSPECT Physics Potential

  Single component HEU core measurement will complement existing LEU spectrum measurements

•  Additional model constraint from single, well modeled, reactor

Oscillation:

  Multiple segmented detectors probe wide L/E span, improving sensitivity over Δm2 range of interest.

•  Phase I can rapidly provide significant physics potential

•  Phase II can address majority of suggested phase space


•  Reactor neutrinos are a tool for discovery. –  Reactors are flavor pure sources of anti-νe for FREE

•  Current reactor experiments (L~1-2km) provide precision data on θ13, and reactor antineutrino flux and spectra. Precision measurements will be input to long-baseline neutrino experiments.

–  Daya Bay, RENO, Double Chooz

•  Medium-baseline experiments (L~60km) may offer <1% precision oscillation physics and a window to the mass hierarchy.

–  JUNO, RENO-50

•  Short-baseline (L~10m) measurements offer opportunities for precision studies of reactor spectrum and a definitive search for short-baseline oscillation and sterile neutrinos.

–  PROSPECT,

Summary & Outlook


Reactor Neutrino Experiments - Miami

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