Simulation study of RENO-50

Jungsic ParkSeoul National University

RENO-50 International WorkshopJune 13-14, 2013

Hoam Faculty House, Korea

Preliminary RENO-50 Detector Concept

25 m

27 m

RENO-50

25 m

27 m

LS (10 kton)

15000 10” PMTs

Mineral Oil

32 m

32 m

Water

KamLAND x 10

1000 10” OD PMTs Concentric cylindrical detector.

- Initial concept is same as RENO.- No gamma-catcher region and filled with Liquid Scintillator Only.

- Install 15000, 10 inch inner PMTs and 1000, 10 inch outer PMTs.

RENO-50 Detector with Monte-Carlo

Target : Acrylic, 25m*25mBuffer : Stainless-Steel, 27m*27mVeto : Concrete, 32m*32m

PMT attachment scheme.

Barrel : 50 raw * 200 column (9*26 for RENO)Interval of each PMT center is 50cm.

Top & Bottom

2501 PMTs for each region. (60 for RENO)45cm

45cm

2700cm

270

0c

m

Energy resolution

Assume that optical properties and thickness of detector materials are same as RENO detector.

For the energy resolution, we generate single gamma of various energy (1~10MeV)at the detector center.

Using the initial concept, we get~7% resolution @ 1MeV and calculated PMT coverage is 24%. PMT coverage : 23.95%

sensitivity test by Monte-Carlo.

Using the Pseudo-experiment , check the sensitivity of θ12 and Δm221 measurement.

True value : varied varied

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221

132

122

.

.

.sin

.sin

m

m

fixed

Measurement of θ12 and Δm221

Assume 10kton * 20GW * 5years exposure

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221

.

.sin

.sin

.

m

m

fixed

222

2

26

1

12

2

11

)()()(

)*(

))(*)(**)(*exp*(

reb

bbkgbkgsignal

r

oscirbkgsignal

feb

NNN

funcefNbNN

Nsignal = 30000 (oscillation , 10kton, 20GW, 5years, 100% efficiency & Livetime )Nbkg = 300 (~1% level)

ε = 1.0 (detection efficiency)b,e, f : pull parameter (e : efficiency, f : reactor)σeff = 0.015 (1.5%)σr = 0.03 (current limit : ~3% goal is below 1%)σb = 0.05 (5%)

Nexpr : Expected event number without oscillationFuncosci(θ12) : oscillation / No oscillation (fraction)

Χ2 fitting with pulls for θ12

True value : 0.8556Fitting value : 0.8552 +- 0.0162 (1σ) ~1.89%

Χ2 fitting result

σeff = 0.015 (1.5%)σr = 0.03 (3%)σb = 0.05 (5%)

Statistics part decrease very rapidly.The main portion is systematic part.

Statistical part only for θ12

Uncertainty of detection efficiency and reactor uncertainty are both important.

Systematical part for θ12

We assumed σb is zero.

222

2

26

1

22111

1

2

)()()(

)*(

))(*)(**)(*exp*(

r

f

e

e

b

b

bibkgNi

bkgNisignalN

rmoscifuncefr

iNbibkgNi

signalNNbin

i

For the Δm221 , we should use the spectrum shape.

N_signal, N_expr N_bkg should be considered bin by bin.Assumed that background is flat. (same number for each bin content)

50bin/MeV 1.8 ~ 8 MeV range cut

Χ2 fitting with pulls for Δm221

ε = 1.0 (detection efficiency)b,e, f : pull parameter (b: background, e : efficiency, f : reactor)σeff = 0.015 (1.5%)σr = 0.03 (current limit : ~3% goal is below 1%)σb = 0.05 (5%)

Systematical part for Δm221

True value : 7.6e-5

Fitting value : (7.598 +- 0.048)e-5 (1σ) ~0.64%

σeff = 0.015 (1.5%)σr = 0.03 (3%)σb = 0.05 (5%)

Expected neutrino visible energy spectrum of RENO-50

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m

m

Energy resolution plays a crucial role to RENO-50

Solid line : Normal HierarchyDashed line : Inverted Hierarchy

So, How can we increase the energy resolution ?

@1MeV

1. Increase the attenuation length of Liquid Scintillator. - 1.5 times current value : 18.7m @ 430 nm - 2.0 times current value : 24.9m @ 430 nm

2. Increase the PMT Quantum Efficiencies. - 1.25 times current value : 30.0% @ 427 nm - 1.5 times current value : 36.0% @ 427 nm

3. Increase the PMT coverage. - 25000 PMTs : 40.86 % coverage

Cf) Default value 24% PMT coverage Att.length of LS is 12.4m @ 430 nm PMT QE is 24% @ 427 nm

Improve the optical properties

24% @ 430 nmMaximum 25% @ 390nm

PMT Quantum Efficiency of R7081 Hamamatsu 10 inch PMT

Mineral OilLiquid Scintillator

Liquid Scintillator : 12.4m @ 430 nmMineral Oil : 17.0m @ 430 nm

Attenuation Length of Current Materials.

Increase the Attenuation Length

Attenuation length should be comparable of detector size.

Increase the PMT Quantum Efficiency

Increase the PMT Coverage

Applying all the Improvement Effect

It’s very challenging task to acquire ~3% energy resolution.

Summary

RENO-50 Monte-Carlo preliminary version was made.

Statistical uncertainty decrease rapidly within few years.

Detection efficiency and reactor uncertainty contributes to systematic a lot.

Including other uncertainty parameters is still keep going.

3% energy resolution is very challenging task. We should improve all the Optical properties about twice. It’s time to think about the improvement method all together.