1. RENO and the Last Result
Jee-Seung Jang
for the RENO collaboration, GIST
International Workshop on RENO-50 toward Neutrino Mass Hierarch
SNU, June 13-14, 2013

2. Contents Introduction to RENO
(Reactor Experiment of Neutrino Oscillations)
Status of RENO
Improvements in data analysis & the last results
Future plan and Summary

3. q13 Measurement in Reactor Experiment
* The Disappearance of Reactor Electron Antineutrino
YongGwang (靈光)
: ~250 km from Seoul
Daya Bay
RENO
Double Chooz

4. RENO Collaboration (12 institutions and 40 physicists)
Chonbuk National University
Chonnam National University
Chung-Ang University
Dongshin University
Gyeongsang National University
Kyungpook National University
Pusan National University
Sejong University
Seokyeong University
Seoul National University
Seoyeong University
Sungkyunkwan University
Total cost : $10M
Start of project : 2006
The experiment is running with both near & far detectors from Aug. 2011

5. RENO Experimental Setup
Far Detector
Near Detector
1380m
290m
120 m.w.e.
Total average thermal output ~16.4 GWth
6 reactors are lined up in roughly equal distances and span ~1.3 km
450 m.w.e.

6. Detection of Reactor Antineutrinos
* Inverse beta decay (IBD)
Neutrino energy measurement

7. Flux Weighted Baselines
RENO Detector
(Gd loaded liquid scintillation detector)
354, 10” Inner PMTs
( 14 % surface coverage )
67, 10” Outer PMTs
Experiments
Location
Thermal Power
(GW)
Flux Weighted Baselines
Near/Far (m)
Depth
Near/Far
(mwe)
Target Mass
(tons)
Statistics
per year
(GW∙ton∙yr)
Double Chooz
France
8.5
[410/1050]
120/300
8.6/8.6 73
RENO
Korea
16.7
409/1444
120/450
16/16
267
Daya Bay
China
17.4
470(576)/1648
250/860
402/80
1392

8. Summary of Detector Construction
2008
2009
2010
2011 6 1 8
Tunnel excavation
Detector structure & buffer steel tanks competed
Acrylic containers installed
PMT test & installation
Detector closing, installation of electronics & Dry run
Liquid scintillator production & filling
Start data taking

9. Finishing the Detector Installation(2011.1)
VETO (Water)
Buffer(Mineral Oil)
Gamma Cather (LS)
Neutrino Target
(Gd+LS)

10. Liquids Filling (2011.6)
Gd-LS filling for Target
Gd Loaded Liquid Scintillator
LS filling for Gamma Catcher
Both near and far detectors are filled with Gd-LS, LS & mineral oil as of July 5, 2011.
Veto water filling was completed at the end of July, 2011.
Water filling for Veto

11. Gd Loaded Liquid Scintillator
Recipe of Liquid Scintillator
(to satisfy chemical, physical, optical properties, and safety requirements)
Aromatic Solvent & Flour
WLS
Gd-compound
LAB
PPO +
Bis-MSB
0.1% Gd+(TMHA)3
(trimethylhexanoic acid)
CnH2n+1-C6H5 (n=10~14)

12. Stability of Gd Concentration
* Stable light yield : ~250 pe/MeV
Nuclear Instruments and Methods
in Physics Research A, 707, ( )
* Stable transparency at 430 nm
* Stable Gd concentration (0.11%)

13. RENO Electronics Software Trigger  High DAQ efficiency
24 channel input
60MHz clock
0.1pC, 0.52nsec resolution
~2500pC/ch large dynamic range
No dead time (w/o hardware trigger)
Fast data transfer via Ethernet R/W
QBEE developed by ICRR for Super-K
(QTC Based Electronics w/ Ethernet)
Software Trigger  High DAQ efficiency
Software trigger selects the events specified by using the timing information
in each hit-data cell
17usec
Periodic Trigger
time
Event# (N-1)
Event# N
Event# (N+1)

14. RENO Status A B C Near Far
Data taking began on Aug. 1, 2011 with both near and far detectors.
(DAQ efficiency : ~95 %)
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
B (403 days) : Improved q13 result
[11 Aug, 2011~13 Oct, 2012]
NuTel 2013
C (~700 days) : Shape+rate analysis
(in progress)
[11 Aug, 2011~31 Jul, 2013]
Absolute reactor neutrino flux measurement in progress
[reactor anomaly & sterile neutrinos]

15. Improvements in the Data Analysis
Statistics :
-- about twice more data
Systematics :
-- Improved background estimation/reduction
(Li/He background, fast N, flasher events)
-- Improved energy scale calibration

16. Energy Scale Calibration
Co 60
(2,506 keV)
Cf 252
(2.2/7.8 MeV)
Ge 68
(1,022 keV)
Cf 252
(2.2/8.0 MeV)

17. Energy Scale Calibration
Far Detector
Near Detector
We found a good calibration function for reactor energy scale.

18. Signature of Reactor Neutrino Event (IBD)
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
Observed spectra for Prompt Signal
Δm212 = 7.6x10-5
sin2(2θ12) =
Δm213 = 2.32x10-3
sin2(2θ13) = 0.113

19. for Delayed Signal (n captured by Gd)
Observed Spectra
for Delayed Signal (n captured by Gd)

20. Detector Stability

21. 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

22. 9Li/8He Background 9Li/8He IBD
9Li/8He are unstable isotopes emitting (b,n) followers and produced when a muon interacts with carbon in the LS.
9Li/8He
IBD

23. Background Spectra Background shapes and rates are well understood
Total backgrounds : 6.5% at Far
2.7% at Near

24. Summary of Final Data Sample
(Prompt energy < 10 MeV)
30211
279787
402.69
369.03
62.0± 0.014
71.4± 0.014
13.73± 2.13
3.61± 0.05
0.60± 0.03
3.61± 0.60
3.14± 0.09
0.68± 0.04
20.48± 2.13
4.89± 0.60
737.69± 2.58
70.13± 0.75

25. Expected Reactor Antineutrino Fluxes
Reactor neutrino flux
- Pth : Reactor thermal power provided by the YG nuclear power plant
- fi : Fission fraction of each isotope determined by reactor core simulation of Westinghouse ANC
- fi(En) : Neutrino spectrum of each fission isotope
[* P. Huber, Phys. Rev. C84, (2011)
T. Mueller et al., Phys. Rev. C83, (2011)]
- Ei : Energy released per fission
[* V. Kopeikin et al., Phys. Atom. Nucl. 67, 1982 (2004)]

26. Observed Daily IBD Rate
Reactor OFF R2 R1 R5 R4 R6 R3
R3+R5+R6
Solid line is predicted rate from the neutrino flux calculation.
Observed points have very good agreement with prediction.
A new way to measure the reactor thermal power remotely!!!

27. Reactor Antineutrino Disappearance
A clear deficit in rate
(7 % reduction)
Consistent with neutrino
oscillation in the spectral
distortion

28. Definite Measurement of Sin22q13
1st result
(PRL)
New result

29. RENO’s Projected Sensitivity of q13
(402 days)
(5.6 s)
(3 years)
(~ 12 s)
(8 % precision)
(18 % precision)
3 years of data : ±0.008 (8% precision)
- statistical error : ±0.010 → ±0.006
- systematic error : ± → ±0.005
(8 % precision)

30. Summary
RENO measured the q13 successfully and stable data taking exceeded 600 days.
RENO improved the systematic uncertainties and
energy calibration after publication of the first result.
-- The clear disappearance of the reactor antineutrinos.
-- New result with 5.6 s
RENO is preparing a new result based on shape analysis.
RENO projects 3 years of data to improve the sensitivity of q13 measurement.

31. Enjoy the conference and Seoul !
Thank you !
&
Enjoy the conference and Seoul !

33. Comparison of Observed Spectra
Finally, we can compare the number of rector anti-neutrino events
observed in our detector with the expectation from the reactor.

34. Detection Efficiency & Systematic Uncertainties

35. Cf Contamination
Tiny fraction of Cf calibration source dissolved into Gd-LS after Oct. 13, 2012 :
- Loose O-ring in the source container → LS into the container
→ Cf out of its disc package → Cf contamination on gloves
→ Cf contamination on the container surface & dissolved into LS
- Cf at the bottom of target (confirmed by event vertex)

36. Cf Contamination
Removal by a multiplicity cut & estimation by its energy shape

37. Observed Daily IBD Rate
Cf contamination
It is the accurate flux measurement.
New methods for remote monitoring of reactor.

38. IBD Prompt Signal (Data vs. MC)
Rb ???