Yoshitaro TakaesuU. of Tokyo

The possibility of determining neutrino properties with Korea related neutrino

experiments.

Introduction

2

opened the window to access the neutrino mass hierarchy (MH)and lepton Dirac CP phase

Reactor

JUNO (DayaBay2)

RENO-50

Mass Hierarchy

3

P (νe → νe) =

3

i = 1

Uei exp − im2

i

2E i

U∗ei

2

= P (νe → νe)

∆ i j =∆m2

i j L

4Eν

Reactor neutrino experiment

νe

Detector

Reactors

6 × 1023 νe/ 3GW/ 15min

4

@ Detectorνe

Reactor neutrino experiment

νe

Detector

Reactors

6 × 1023 νe/ 3GW/ 15min

5

PMT

Inside Detector (Inverse Beta Decay)

MH difference in spectrumνe

6

δE

E=

a%√

E

dN

dE obsvis

=NpT

4πL 2

∞

E t h r

dEν φ(Eν ) Pee(Eν , L , MH, · · · ) σIBD (Eν ) G(Evis − E obsvis ,δEvis)

NHIH

Sensitivity

7

Sensitivity to the Mass hierarchy

The typical sensitivity curve of this experiment

Small flux

8

Vvvv vvv

Effects of to the sensitivity

L = 30km

L = 50km

9

0%

2.5%

-2.5%

δ(|∆ m231|)

|∆ m231|

10 20 30 40 50 60 70 80 90 km

Sensitivity to the Mass hierarchy

The typical sensitivity curve of this experiment

Small flux

10

Vvvv vvv

Effect of Energy resolution

11

δE

E=

a%√

E

Effect of Energy resolution

18kton 16.5GW 5yrs

Current value

NH

δE

E=

a

E / MeV

2

+ b2

12

Effect of Energy Resolution 2

δE

E=

a√

E

2

+ b2

18kton 16.5GW 5yrs

20 30 40 50 60 70 80 90 100

L [km]

b = 0%

0.5%

0.75%

1%

a = 3%a = 2%

b = 0 b = 1% Sensitivity 40%

Imrovement of b term is also important13

Current value

How to achieve better Energy Resolution?

Increase the photo-electron (p.e.)detected by PMT.

p.e.~ 200 pe/MeV ~ 2000 pe/MeV

Ex)

• Increase PMT coverage

• Increase QE of PMT

• More transparent LS

14

~ 6% ~ 2%

25m 35%

δE

E=

3.7%

E/ MeV

Energy Resolution (simulation)

J.S. Park (RENO)

δE

E=

4.4%

E/ MeV

δE

E=

4.4%

E/ MeV

Interference Effect

16

E. Ciuffoli, J. Evslin, X. Zhang: 1302.0624Y-F. Li, J. Cao, Y. Wang, L. Zhan: 1303.6733

ΔL = L1 – L2

Reactor1

Multi-reactor interference

L1 L2

17

Reactor1 + Reactor2

multi-cores

Multi-reactor interference 16.5GW

18kton 5yrs

a = 3%, b = 0.5%δE

E=

a√

E

2

+ b2

(∆ χ2)min

All Reactors50 km

18

250m

Parameter Measurement

19

Parameter measurement

< 0.5% accuracy

can be measured accurately @ L ~ 50 km

L = 50km

1%

1%

1%

1%

* Effect of energy scale unc. Is not considered.

Summary: Reactor neutrinoFuture Reactor neutrino Experiment for MH determination

For > 3-sigma determination within 5 years

a < 3%

b < 0.5%

of Energy Resolution is required

with 16.5GW 18kton Reactor Complex.

Interference among reactor cores significantly affects the sensitivity.

•Energy Scale uncertainty should be controlled very carefully.arXiv: 0901.2976, 1208.1551, 1308.0591

* Neutrino parameters can be determined with < 1% accuracy.

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