1. “RENO/RENO-50” K.K. Joo Chonnam National University
(On behalf of RENO Collaboration)
August 23, 2016
NuFact Quy Nhon, Vietnam

2. Neutrino Mixing Angles
SNO, Super-K;
KamLAND
Solar Neutrino Oscillation
Atmospheric Neutrino Oscillation
Reactor Neutrino Oscillation
q12
q23
q13
9o (2012)
Daya Bay, RENO
Double Chooz
~45o (1998)
Super-K; K2K
2015
Nobel
Prize
“Neutrino has mass”
“Established three-flavor mixing framework”

3. RENO Collaboration Reactor Experiment for Neutrino Oscillation
9 institutions and 35 physicists in Korea
Chonnam National 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 since Aug. 2011
YongGwang (靈光) :
New name: Hanbit
Reactor Experiment for Neutrino Oscillation

4. YongGwang Nuclear Power Plant
100m
300m
70m high
200m high
1,380m
290m
Far Detector
Near Detector
Reactors
Google Satellite View of Experimental Site
16.5 GWth
120 m.w.e.
290m
6 reactors are lined
up in roughly equal
distances and
span ~1.3 km
Total average
thermal output
~16.5GWth
YongGwang Nuclear Power Plant
1380m

5. RENO Detector 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 (MO)
(R=2.7m, H=5.8m)
Veto : 350 ton water (R=4.2m, H=8.8m)
Inner PMTs: ” PMTs
solid angle coverage = ~14%
Outer PMTs: ~ 67 10” PMTs
total ~460 tons

6. IBD signal: coincidence
Inverse beta decay (ve + p e+ + n)
Prompt signal (S1)
Delayed signal (S2)
n-Gd IBD
~30 ms
8 MeV
n-H IBD S1 S2
~200 ms
2.2 MeV
Sunny Seo

7. RENO Data-taking Status
Data taking began on Aug. 1, 2011 with both near and far detectors.
(DAQ efficiency : ~95%) A B C D
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 (~500 days) : New result
Shape+rate analysis (q13 and |Dmee2 |)
[11 Aug, 2011~21 Jan, 2013]
PRL 116, (2016)
D (~1400 days) : Absolute reactor flux and spectrum
[11 Aug. 2011~ 30 Sep, 2015]
Total ~ 1700 days

8. Observed Delayed Signal (n-Gd)
IBD (ve + p e+ + n)
Delayed energy distribution (S2)

9. Measured Spectra of IBD Prompt Signal
Our DAQ Livetime is about 800 days
And background is 3% on Far and 6 % on NEAR
Near Live time = days
# of IBD candidate = 290,775
# of background = 8,041 (2.8 %)
Far Live time = days
# of IBD candidate = 31,541
# of background = (4.9 %)

10. IBD Candidates & Backgrounds
Near
Far
DAQ live time
(days)
458.49
489.93
IBD candidates
290755
31541
Total BKG rate
(/day)
17.54± 0.83
3.14± 0.21
IBD rate (/day)
after BKG subtraction
616.67± 1.44
61.24± 0.42

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

12. The 5 MeV Excess is there ! In 2014, RENO showed that the 5 MeV excess
Double Chooz
Daya Bay
Neutrino 2014, Boston
In 2014, RENO showed that the 5 MeV excess
is from reactor neutrinos.
Seon-Hee Seo, SNU
Hawaii 2014

13. Observation of an excess at 5 MeV
(Preliminary)
1400 days of data
(Aug – Sep 2015)
Fraction of 5 MeV excess: ± 0.27 (%)
~3%
~2.5%

14. Correlation of 5 MeV Excess with Reactor Power
1400 days of data
5 MeV excess
has a clear
correlation
with reactor
thermal power !
two or three reactors are off
All the six reactors are on
The 5 MeV excess comes from reactors!

15. Measurement of Absolute Reactor Neutrino Flux
R (data/prediction) = (500 days)
The flux prediction is with Huber + Mueller model
Flux weighted baseline at near : 411 m
Comparison with other experiments
Preliminary
Daya Bay
*Prediction is corrected for three flavor neutrino oscillation

16. Reactor Neutrino Oscillations
Probability νe
1.0
flux before oscillation observed here
Oscillations observed as a deficit of anti-neutrinos
sin22θ13
the position of the minimum is defined by Δm2ee
Distance
1200 to 1800 meters
H. Nunokawa et al,
PRD (2005)

17. Energy Calibration from g-ray Sources 12B Energy Spectrum (Near & Far)
Electron energy spectrum from β-decays from 12B and 12N,
which are produced by cosmic-muon interactions
Non-linear resonse of the scintillation energy is calibrated using γ-ray source
Fit function : Evis/Etrue = a – b/(1 – exp(-cEtrue – d))
Deviation of all calibration data points with respect to the best-fit is within ~1%
Good agreement between
data and MC spectrum!

18. Energy Dependent Disappearance L/E Dependent Disappearance
PRL 116, , 2016
Clear energy-dependent disappearance of reactor antineutrinos

19. Summary of New Oscillation Results
Rate Only
± 0.011(total)
Rate + Shape
± 0.26 (total)
10 % precision
± 0.010(total)
12 % precision
arXiv: v2
PRL 116, (2016)

20. Projected Sensitivity of q13 & |Dmee2|
(±12%)
(5 years of data)
(±6 %)
(±10%)
(~500 days)
(6 % precision)
(sensitivity goal of q13 )
CERN

21. n-H IBD Event Vertex Distribution
n-H IBD Analysis
Motivation:
1. Independent measurement of q13 value.
2. Consistency and systematic check on reactor neutrinos.
n-H IBD Event Vertex Distribution
target
g-catcher
Seon-Hee Seo, SNU

22. q13 Measurement with n-H Preliminary rate only analysis results is
Uncertainty
Detection efficiency
0.59%
Thermal power
0.5 %
Isotope fraction
0.7 %
Background
Near : 0.2%
Far : 0.8%
Data set : 2011/08 ~ 2013/01 (~500 days)
Preliminary rate only analysis results is

23. Summary (1st part) ± 0.26(total) ± 0.010(total)
New measurement of q13 by rate-only analysis
Observed an excess at 5 MeV in reactor neutrino spectrum
Observation of energy dependent disappearance of reactor neutrinos and our first measurement of Dmee2
± 0.26(total)
10 % precision
± 0.010(total)
12 % precision
RENO (goal): sin(2q13) to 6% accuracy
Dmee2 to 0.15×10-3 eV2 (6%) for final sensitivity

24. 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 Dm2ee Supernova neutrinos, Geo neutrinos, Sterile neutrino search, ….
Budget : $ 100M for 6 year construction (Civil engineering: $ 15M, Detector: $ 85M)
Schedule : ~ 2021 : Facility and detector construction ~ : Operation and experiment

25. RENO-50 18 kton LS Detector ~47 km from YG reactors
Far Detector
Near Detector
RENO-50
18 kton LS Detector ~47 km from YG reactors
Mt. Guemseong (450 m) ~900 m.w.e. overburden
Courtesy by YoshitaroTakaesu
(Tokyo)
(NEAR Detector)
(FAR Detector)

26. RENO-50 Candidate Site Dongshin University RENO-50 Candidate Site
Mt. GuemSeong
Altitude : 450 m
Dongshin University
RENO-50 Candidate Site
City of Naju

27. Geological Survey for Underground Facility
Conceptual Design of RENO-50 Detector
39 m
LS (18 kton)
” PMTs
Water, ” PMTs
RENO-50 detector (MC)
Cost estimation for RENO-50 underground facility (in progress)
 Geological survey for design of tunnel and experimental hall
 Cost estimation to be obtained soon

28. RENO-50 R&D Status in Progress
(1) Development of DAQ electronics is on-going
(2) Develop techniques of LS purification is on-going
(3) Mechanical design of detector is on-going
(4) Measurement of radioactivity for the detector materials is on-going
(5) Upgrade of measurement device for absolute LS attenuation
length is on-going
Current status
An R&D funding (US $2M for 3 years of ) is given by the Samsung Science & Technology Foundation.
Efforts on obtaining a full construction fund

29. T2HKK (Korea option)
The T2K n beam will come to Korea. (2nd osc. maximum)
Hyper-K
Give T2K the capability to provide n mass ordering sensitivity
T2HKK session
@KPS (Oct. 22)
HK members are welcome
2.5 deg. off axis
2.5 deg. off axis
~1100km
2.5deg.off-axis beam @Kamioka
JPARC
see hep-ph/ )
Off-axis angle

30. Summary of RENO/RENO-50 Independent measurement of q13 with n-H
New results are presented
Clear observation of 5 MeV excess
Absolute antineutrino flux measurement (R = )
Independent measurement of q13 with n-H
RENO-50: various R&D in progress
In addition, T2HKK option will be considered seriously

32. Correlation of 5 MeV excess with 235U isotope fraction
(Preliminary)
235U fraction corresponds to freshness of reactor fuel
Fit function χ2
y = p0
1.407
y = p0 + p1*x
0.233
Δχ2 = 1.174
P-value = 0.240
(End
of reactor cycle)
(Beginning
of reactor cycle)

33. Energy Scale Difference between Near & Far
Energy scale difference < 0.15% for Ep = 1~8 MeV

34. Delayed spectrum and capture time
Delayed signal peak:
~2.2 MeV
Mean coincidence time:
~ 200 ms
Capture time (n-H)
Far and near data match very well 34

35. Light Sterile Neutrino Search Results
All 500 days of RENO data
Consistent with standard 3-flavor
neutrino oscillation model
Able to set stringent limits in
the region
(Preliminary)
eV2
full curves assumes

36. Various Physics with RENO-50
Determination of neutrino mass ordering
- 3s sensitivity with 10 years of data
Precise (~0.5%) measurement of q12, Dm221 and Dm2ee
- An interesting test for unitarity & essential for the future discoveries
Neutrino burst from a Supernova in our Galaxy
- Study the core collapsing mechanism with neutrino cooling
Geo-neutrinos : ~ 1,500 geo-neutrinos for 5 years
- Study the heat generation mechanism inside the Earth
Solar neutrinos
- MSW effect on neutrino oscillation
Sterile neutrino search : reactor / radioactive sources / IsoDAR
Detection of J-PARC beam : ~200 events/year