1. Recent Results from RENO & Future Plan
Soo-Bong Kim (KNRC, Seoul National University)
“Fermilab, July 25, 2014”

2. Remembrance
Yoji Totsuka, who discovered the neutrino oscillation, was a big supporter for the RENO experiment.
I would like to remember him with our RENO results on q13.
Yoji Totsuka (1942~2008)
Credit to L. Mikaelyan & V. Sinev for two identical detectors
Maury Goodman’s neutrino newsletter (5/5/2012):
F. Darwin said “In Science the credit goes to the man who convinces the world, not to the man to whom the idea first occurred.”
But he wishes to give credit to Russians who first proposed a two detector neutrino reactor disappearance experiment : L. Mikaelyan & V. Sinev.

3. Reactor 13 Experiments RENO at Yonggwang, Korea
Daya Bay at Daya Bay, China
Double Chooz at Chooz, France

4. q13 Reactor Neutrino DetectorsMO LS
H2O
Gd-LS

5. RENO Collaboration Reactor Experiment for Neutrino Oscillation
(11 institutions and 40 physicists)
Chonbuk National University
Chonnam National University
Chung-Ang University
Dongshin University
GIST
Gyeongsang National University
Kyungpook National University
Sejong University
Seoul National University
Seoyeong University
Sungkyunkwan University
Total cost : $10M
Start of project : 2006
The first experiment running with both near & far detectors from Aug. 2011
YongGwang (靈光) :

6. RENO Experimental Set-up
Far Detector
Near Detector
1380m
290m
120 m.w.e.
450 m.w.e.

7. RENO Detector 354 ID +67 OD 10” PMTs
Target : 16.5 ton Gd-LS, R=1.4m, H=3.2m
Gamma Catcher : 30 ton LS, R=2.0m, H=4.4m
Buffer : 65 ton mineral oil, R=2.7m, H=5.8m
Veto : 350 ton water, R=4.2m, H=8.8m

8. RENO Status Near Detector A Far Detector B C (new results) Now
Data taking began on Aug. 1, 2011 with both near and far detectors.
(DAQ efficiency : ~95%) A
Near Detector B C
(new results)
Far Detector
Now
A (220 days) : First q13 result
[11 Aug, 2011~26 Mar, 2012]
PRL 108, (2012)
B (403 days) : Improved q13 result
[11 Aug, 2011~13 Oct, 2012]
NuTel 2013, TAUP 2013, WIN 2013
C (~800 days) : New q13 result Shape+rate analysis (in progress)
[11 Aug, 2011~31 Dec, 2013]
Total observed reactor neutrino events as of today : ~ 1M (Near), ~ 0.1M (Far)
→ Absolute reactor neutrino flux
measurement in progress
[reactor anomaly & sterile neutrinos]

9. Detection of Reactor Antineutrinos
(prompt signal)
(delayed signal)
~200 ms
+ p  D + g (2.2 MeV)
~26 ms
(0.1% Gd)
+ Gd  Gd + g‘s (8 MeV)
Neutrino energy measurement

10. Gd Loaded Liquid Scintillator
Recipe of Liquid Scintillator
Solvent & Flour
WLS
Gd-compound
LAB
PPO + Bis-MSB
0.1% Gd + (TMHA)3
Steady properties of Gd-LS
Stable light yield (~250 pe/MeV) , transparency & Gd concentration (0.11%)
NIM A, 707, ( )

11. Liquid(Gd-LS/LS/MO/Water) Production & Filling
(May-July 2011)
Gd Loaded Liquid Scintillator
Gd-LS filling for Target
Gd Loaded Liquid Scintillator
LS filling for Gamma Catcher
Water filling for Veto

12. Yonggwang Neutrino Detector Facility
3~6인 상주 : 검출시설 관리 및 작동 (발전소 사택 아파트 2채 임대 사용 중)

13. New RENO Results at Neutrino 2014
■ ~800 days of data
■ New measured value of q13 from rate-only analysis
■ Observation of a new reactor neutrino component at 5 MeV
■ Results of reactor neutrinos with neutron capture on H

14. IBD Event Signature
Prompt signal (e+) : 1 MeV 2g’s + e+ kinetic energy (E = 1~10 MeV)
Delayed signal (n) : 8 MeV g’s from neutron’s capture by Gd
~26 ms (0.1% Gd) in LS
Delayed Signal →
Prompt Signal

15. Neutron Capture by Gd

16. Backgrounds m n m n m 9Li g p e n
Accidental coincidence between prompt and delayed signals
Fast neutrons produced by muons, from surrounding rocks and inside detector (n scattering : prompt, n capture : delayed)
9Li/8He b-n followers produced by cosmic muon spallation
Accidentals
Fast neutrons
9Li/8He b-n followers m n Gd m n m
9Li g p e Gd n Gd

17. Measured Spectra of IBD Prompt Signal
Bkg.: 2.2 %
Bkg.: 7.2 %
Near Live time = days
# of IBD candidate = 433,196
# of background = (2.2 %)
Far Live time = days
# of IBD candidate = 50,750
# of background = (7.2 %)

18. Observed Daily Averaged IBD Rate
preliminary
Good agreement with observed rate and prediction.
Accurate measurement of thermal power by reactor neutrinos

19. Observed vs. Expected IBD Rates
sin22q13 = 0.101
|Δm312| = 2.32 x 10-3 eV2
- Good agreement between observed rate & prediction
- Indication of correct background subtraction

20. New q13 Measurement by Rate-only Analysis
(Preliminary)
4.9 s (Neutrino 2012)
 s (TAUP/WIN 2013)
 / s (Neutrino 2014)

21. Why n-H IBD Analysis? Motivation:
1. Independent measurement of q13 value.
2. Consistency and systematic check on reactor neutrinos.
* RENO’s low accidental background makes it possible
to perform n-H analysis.
-- low radio-activity PMT
-- successful purification of LS and detector materials.

22. IBD Sample with n-H Neutron-H Capture cut criteria preliminary
Prompt Energy
0.7 ~ 12 MeV
Delayed Energy
1.95~2.50 MeV
deltaT
2 ~ 400 us
deltaR
< 50 cm
Qmax/Qtot
< 0.08
Muon Veto time
1 ms
Shower Muon Veto time
700 ms
Additional Trigger veto time cuts
n-H IBD Event Vertex Distribution
target
g-catcher

23. Results from n-H IBD sample
Very preliminary
Rate-only result
(B data set)
Near Detector
preliminary
Far Detector
preliminary

24. Reactor Neutrino Oscillations
Short Baseline
Long Baseline
[Nunokawa & Parke (2005)]
cos 2 𝜃 12 Δ 𝑚2 21

25. Energy Calibration from g-ray Sources

26. Energy Calibration from B12 b-decays
Near detector

27. Far detector

28. B12 Energy Spectrum (Near & Far)

29. Interacting Reactor Isotope Fraction
Averaged from the six reactors

30. Observation of a New Reactor Neutrino Component at 5 MeV
Fraction of 5 MeV excess (%) to expected flux [2011 Huber+Mueller]
Near : / (experimental) +/ (expected shape error)
Far : / (experimental) +/ (expected shape error)

31. Correlation of 5 MeV Excess
with Reactor Power
5 MeV excess
has a clear
correlation
with reactor
thermal power !
All the six reactors are on
two or three reactors are off
A new reactor neutrino component !!

32. Observed Spectra of IBD Prompt Signal
The expected IBD prompt spectra from the RENO MC do not reproduce the shape in the energy region of 4~6 MeV.....
Near Detector
(BG: 2.7%)
Far Detector
17102 (BG: 5.5%)
RENO slide from Neutrino 2012, Kyoto
Need more detailed energy calibration between 3 and 8 MeV using new radioactive sources.
Any new components of background sources?
Is the prediction of reactor neutrino spectra correct??

33. The 5 MeV Excess Seen at Double-Chooz Double-Chooz, Neutrino 2014
and Daya Bay
Daya Bay, ICHEP 2014
Double-Chooz, Neutrino 2014

34. Shape Analysis for Dmee2 In progress…. Stay tuned…
Without 5 MeV excess
With 5 MeV excess

35. RENO’s Projected Sensitivity of q13
Neutrino 2014
(~800 days)
(7.8 s)
(in 3 years)
(14 s)
(7 % precision)
(13 % precision)
5 years of data : ±7%
- stat. error : ±0.008 → ±0.005
- syst. error : ±0.010 → ±0.005
- shape information → ±5%
(7 % precision)

36. A Brief History of q13 from Reactor Experiments
DC: 97 days [ ]
R+S
DB: 49 days [ ]
RENO: 222 days [ ]
DC: 228 days [ ]
DB: 139 days [ ]
DC: n-H [ ]
RENO: 403 days [NuTel2013]
DC: RRM analysis [ ]
DB: 190 days [ ]
RENO: 403 days [TAUP2013]
DB: 190 days n-H [Moriond2014]
DC: 469 days [n 2014]
DB: 563 days [n 2014]
RENO: 795 days [n 2014]
384 days n-H [n 2014]

37. 13 from Reactor and Accelerator Experiments
First hint of δCP combining Reactor and Accelerator data
Best overlap is for
Normal hierarchy & δCP = - π/2
Is Nature very kind to us?
Are we very lucky?
Is CP violated maximally?
Strong motivation for
anti-neutrino runs and precise measurements of θ13
Courtesy C. Walter (T2K Collaboration)
Talk at Neutrino 2014

38. Summary We observed a new reactor component at 5 MeV. (3.6 s)
(preliminary)
New measurement of q13 by rate-only analysis
Shape analysis for Dm2 in progress… (stay tuned)
(very preliminary)
First result on n-H IBD analysis
sin2(2q13) to 7% accuracy within 3 years
→ will provide the first glimpse of CP.
If accelerator results are combined.

39. Overview of RENO-50
RENO-50 : An underground detector consisting of 18 kton ultra- low-radioactivity liquid scintillator & 15,000 20” PMTs, at 50 km away from the Hanbit(Yonggwang) nuclear power plant
Goals : - Determination of neutrino mass hierarchy High-precision measurement of q12, Dm221 and Dm Study neutrinos from reactors, the Sun, the Earth, Supernova, and any possible stellar objects
Budget : $ 100M for 6 year construction (Civil engineering: $ 15M, Detector: $ 85M)
Schedule : ~ 2019 : Facility and detector construction ~ : Operation and experiment

40. Reactor Neutrino Oscillations at 50 km
Neutrino mass hierarchy (sign of Dm231)+precise values of 12, Dm221 & Dm231
Precise Dm221
Precise q12
Large Deficit
Mass Hierarchy
Ripple

41. RENO-50 10 kton LS Detector ~47 km from YG reactors
Far Detector
Near Detector
RENO-50
10 kton LS Detector ~47 km from YG reactors
Mt. Guemseong (450 m) ~900 m.w.e. overburden
(NEAR Detector)
(FAR Detector)

43. 2012 Particle Data Book Precise measurement of q12, Dm221 and Dm232
(±2.8%)
sin2q12 = 0.312± (±5.4%)
(±2.7%)
(±3.1%)
∆m212 / |∆m31(32)2| ≈ 0.03
( %)
(±13.3%)
Precise measurement of q12, Dm221 and Dm232
(← 5.4%)
(← 2.7%)
(← 5.2%)

44. Additional Physics with RENO-50
Neutrino burst from a Supernova in our Galaxy
- ~5,600 events kpc) (* NC tag from 15 MeV deexcitation g)
- A long-term neutrino telescope
Geo-neutrinos : ~ 1,000 geo-neutrinos for 5 years
- Study the heat generation mechanism inside the Earth
Solar neutrinos : with ultra low radioacitivity
- MSW effect on neutrino oscillation
- Probe the center of the Sun and test the solar models
Detection of J-PARC beam : ~200 events/year
Neutrinoless double beta decay search : possible modification like KamLAND-Zen

45. J-PARC neutrino beam
Dr. Okamura & Prof. Hagiwara
RENO-50

46. Thanks for your attention!