1. Simulation study of RENO-50 Jungsic Park Seoul National University RENO-50 International Workshop June 13-14, 2013 Hoam Faculty House, Korea

2. 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 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.

3. RENO-50 Detector with Monte-Carlo Target : Acrylic, 25m*25m Buffer : Stainless-Steel, 27m*27m Veto : 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 2700cm

4. 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%

5. sensitivity test by Monte-Carlo. Using the Pseudo-experiment, check the sensitivity of θ 12 and Δm 2 21 measurement. True value : varied varied fixed Measurement of θ 12 and Δm 2 21 Assume 10kton * 20GW * 5years exposure fixed

6. 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) σ eff = 0.015 (1.5%) σ r = 0.03 (current limit : ~3%  goal is below 1%) σ b = 0.05 (5%) Nexp r : Expected event number without oscillation Func osci (θ 12 ) : oscillation / No oscillation (fraction) Χ 2 fitting with pulls for θ 12

7. True value : 0.8556 Fitting value : 0.8552 +- 0.0162 (1σ)  ~1.89% Χ 2 fitting result σ eff = 0.015 (1.5%) σ r = 0.03 (3%) σ b = 0.05 (5%)

8. Statistics part decrease very rapidly. The main portion is systematic part. Statistical part only for θ 12

9. Uncertainty of detection efficiency and reactor uncertainty are both important. Systematical part for θ 12 We assumed σ b is zero.

10. For the Δm 2 21, we should use the spectrum shape. N_signal, N_exp r 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 Χ 2 fitting with pulls for Δm 2 21 ε = 1.0 (detection efficiency) b,e, f : pull parameter (b: background, e : efficiency, f : reactor) σ eff = 0.015 (1.5%) σ r = 0.03 (current limit : ~3%  goal is below 1%) σ b = 0.05 (5%)

11. Systematical part for Δm 2 21 True value : 7.6e -5 Fitting value : (7.598 +- 0.048)e -5 (1σ)  ~0.64% σ eff = 0.015 (1.5%) σ r = 0.03 (3%) σ b = 0.05 (5%)

12. Expected neutrino visible energy spectrum of RENO-50

13. Energy resolution plays a crucial role to RENO-50 Solid line : Normal Hierarchy Dashed line : Inverted Hierarchy So, How can we increase the energy resolution ? @1MeV

14. 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

15. 24% @ 430 nm Maximum 25% @ 390nm PMT Quantum Efficiency of R7081 Hamamatsu 10 inch PMT

16. Mineral Oil Liquid Scintillator Liquid Scintillator : 12.4m @ 430 nm Mineral Oil : 17.0m @ 430 nm Attenuation Length of Current Materials.

17. Increase the Attenuation Length Attenuation length should be comparable of detector size.

18. Increase the PMT Quantum Efficiency

19. Increase the PMT Coverage

20. Applying all the Improvement Effect It’s very challenging task to acquire ~3% energy resolution.

21. 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.