RENO Reactor Neutrino Experiment

RENO & RENO-50
RENO = Reactor Experiment for Neutrino Oscillation(On behalf of RENO Collaboration)

K.K. Joo
Chonnam National University
March 15, 20132013 ICRR Neutrino Workshop @ Kashiwa campus

Past Efforts for Finding q13
 Chooz (2003) & Palo Verde (2000): No signal
sin2(2q13) < 0.12 at 90% C.L.
 T2K : 2.5 s excess (2011)
0.03 < sin2(2q13) < 0.28 at 90% C.L. for N.H.

 Daya Bay (03. 08. 2012)
5.2 s observationsin2(2q13) = 0.092 ±0.016(stat.)±0.005(syst.)

0.04 < sin2(2q13) < 0.34 at 90% C.L. for I.H.
 MINOS : 1.7 s excess (2011)
0 < sin2(2q13) < 0.12 at 90% C.L. for N.H.
0.04 < sin2(2q13) < 0.19 at 90% C.L. for I.H.

 Double Chooz : 1.7 s measurement (2011)
sin2(2q13) = 0.086 ± 0.041(stat.) ± 0.030(syst.)

RENO Result

Outline
RENO Introduction
 Experimental setup & detector
 Data-taking & data set
 Improvements in data analysis
 Results
 Summary
RENO-50

 Introduction
 Physics with RENO-50
 SummaryNeutrino Mixing Parameters

Matrix Components:
3 Angles (θ12; θ13; θ23)
1 CP phase (δ)
2 Mass differences01
U   0 c23
0  s230  c13s23  0
c23   s13e iatmospheric SK, K2K

q23≈qatm ≈ 45°
Large and maximal mixing!

 ν e   U e1   ν μ    U μ1ν  U τ   τ1

U e2
U μ2
U τ2

U e3  ν1  
U μ3  ν 2 U τ3  ν 3 

0 s13e  c12

1
0   s12
0 c13  0

s12 0 
c12 0 0 1 i

The Next Big Thing?

SNO, solar SK, KamLAND

q12 ≈qsol ≈ 32°

Neutrino Oscillation
Neutrino: elementary particle

Three types of neutrinos exist &mixing among themOscillation parameters(q12 , q23 , q13)

Reactor Antineutrino Oscillation
2


1
.
27

m
2
2
13L

P( e   e )  1  sin 2q13 sin E

Trying to measure
preciselyDisappearance

Reduction of reactor neutrinos due to oscillations

Reactor neutrino disappearance Prob. due
to q13 with the allowed 2s range in m232

 sin22q13 > 0.01 with 10 t •14GW •3yr ~ 400 t•GW•yr(400 t•GW•yr: a 10(40) ton far detector and a 14(3.5) GW reactor in 3 years)

RENO Expected Sensivity
90% CL Limitssin2(2q13) > 0.02
3 yrs

RENO

• 10 times better
sensitivity thanthe current limit
G. Fogli et al.
(2009)Chooz

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+++ http://reno01.snu.ac.kr/RENOYongGwang Nuclear Power Plant
 Located in the west coast of southern

YongGwang(靈光):part of Korea
 ~400 km from Seoul 6 reactors are lined up in roughly equal
distances and span ~1.3 km
 Total average thermal output ~16.4GW th(2nd largest in the world)= glorious[splendid] light(~spirited)Near Detector

70m high

Google Satellite View of Experimental Site

200m highReactors

100m

300m
290m

1,380mYongGwang Nuclear Power Plant

Far Detector

RENO Detector• Inner PMTs: 342 10” PMTs
• solid angle coverage = 12.6%• Outer PMTs: ~ 60 10” PMTs

Thick
(cm)

vesselMaterial

Mass(tons)

Target140

Acrylic(10mm)

Gd(0.1%)
+LS

15.4

Gamma
catcher60

Acrylic(15mm)

LS

27.5

Buffer70

SUS(5mm)Mineral
oil

59.2

Veto

150

Steel
(15mm)

water

354.7

total ~460 tons

Summary of Detector Construction
 2006. 03 : Start of the RENO project 2008. 06 ~ 2009. 03 : Civil construction including tunnel excavation
 2008. 12 ~ 2009. 11 : Detector structure & buffer steel tanks
completed 2010. 06 : Acrylic containers installed 2010. 06 ~ 2010. 12 : PMT test & installation
 2011. 01 : Detector closing/ Electronics hut & control room built
 2011. 02 : Installation of DAQ electronics and HV & cabling 2011. 03 ~ 06 : Dry run & DAQ debugging
 2011. 05 ~ 07 : Liquid scintillator production & filling 2011. 07 : Detector operation & commissioning 2011. 08 : Start data-taking

by KOATECH Co. Korea(2009.7~2010.6)

PMT Mounting (2010. 8~10)

PMT Mounting (2010. 8~10)

Detector Closing (2011. 1)

Near : Jan. 21, 2011

Far : Jan. 24, 2011

Data Acquisition System• 24 channel PMT input to ADC/TDC• 0.1pC, 0.52nsec resolution• ~2500pC/ch large dynamic range• No dead time (w/o hardware trigger)• Fast data transfer via Ethernet R/WPrinciple of Neutrino Detection

γ(0.511MeV)e-

 Use inverse beta decay (ve + p e+ + n)νreaction process
promptsignalp
 Prompt part:nsubsequent annihilation of the positron
Delayed signal
30μs
to two 0.511MeV γγ Delayed part:Gd E ~ 8MeV neutron is captured
γ~200ms w/o Gdγ~ 30ms w Gd
Gd has largest n absorption cross section &emits high energy 
Signal Property
 Signal from neutron capture
1~8MeV~2.2MeV w/o Gd
8MeV
30μs
~ 8MeV w Gd
 Measure prompt signal & delayed signalt “Delayed coincidence” reduces
backgrounds drasticallye+eγ(0.511MeV)

Gd Loaded Liquid Scintillator

CnH2n+1-C6H5 (n=10~14)

 Recipe of Liquid Scintillator

•
•
•
•
•
•
•

Aromatic Solvent &
Flour

WLS

Gd-compound

LAB

PPO +
Bis-MSB

0.1% Gd+TMHA(trimethylhexanoic acid)

High Light Yield : not likely Mineral oil (MO)replace MO and even Pseudocume (PC)Good transparency (better than PC)
High flash point : 147oC (PC : 48oC)
Environmentally friendly (PC : toxic)
Components well known (MO : not well known)
Domestically available: Isu Chemical Ltd.

 Solvent-solvent extraction method

RCOOH  NH3  H 2O  RCOONH4  H 2O
3RCOONH4 (aq)  GdCl3 (aq)  Gd(RCOO)3  3NH4Cl

 0.1% Gd compounds with CBX (Carboxylic acids; R-COOH)- CBX : TMHA (trimethylhexanoic acid)Liquid Production System (2010. 11~2011. 3 )Stability of Gd Concentration* Stable light yield : ~250 pe/MeV* Stable Gd concentration (0.11%)

Nuclear Instruments and Methods
in Physics Research A, 707, 45-53(2013. 4. 11)

Stability of Transmittance [T]* Shimadzu UV-1800 spectrophotometer* Stable transparency at 430 nm* Stable : ~450 days (2011.09 ~ present)Data-Taking & Data Set
 Data taking began on Aug. 1, 2011
with both near and far detectors.
 Data-taking efficiency > 90%.

 Trigger rate at the threshold energyof 0.5~0.6 MeV : 80 Hz @ FD
 Data-taking period : > 510 days
Aug. 11, 2011 ~ present
Event rate before reduction
208Tl
40K

2 MeV

n capture by Gd

6 MeV

10 MeV Data-taking efficiency

IBD Event Signature and Backgrounds
 IBD Event Signature Prompt signal (e+) : 1 MeV 2’s + e+ kinetic energy (E = 1~10 MeV)

 Delayed signal (n) : 8 MeV ’s from neutron’s capture by Gd
Prompt Energy

Delayed Energy Backgrounds

 Accidental backgrounds which mimic IBD Event 9Li/8He b-n followers produced by cosmic muon spallation

 Fast neutrons produced by muons, from surrounding rocks and insidedetector (n scattering : prompt, n capture : delayed)Improvements in Data Analysis

9Li/8He b-n Backgrounds

Effectively we can remove sparking backgrounds

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 contamination on gloves and the container surface →dissolved into LS- Cf at the bottom of target (confirmed by event vertex)

Cf Contamination
Most of Cf events were removed by a multiplicity cut andremained Cf events in IBD events were estimated by its energy shape.

Beforeremoving

Observed Daily IBD Rate

Cf contamination

 Solid line is predicted rate from the neutrino flux calculation.
 Observed points have very good agreement with prediction.
 It’s the accurate flux measurement.

1D/3D Calibration System (2010. 8 ~ 2011. 7)
Two identical source driving systems at the center of TARGET and one side of GAMMA CATCHER

Mechanical system

Glove box

Control system

Energy Scale Calibration

Co 60

Ge 68
(1,022 keV)

(2,506 keV)

Cf 252(2.2/8.0 MeV)
Cf 252(2.2/7.8 MeV)

Energy Scale Calibration
Far Detector

Near Detector

IBD Event Selection
 Reject flashers and external gamma rays : Qmax/Qtot < 0.03
 Muon veto cuts : reject events after the following muons(1) 1 ms after an ID muon with E > 70 MeV, or with 20 < E < 70
MeV and OD NHIT > 50
(2) 10 ms after an ID muon with E > 1.5 GeV

 Coincidence between prompt and delayed signals in 100 ms- Eprompt : 0.7 ~ 12.0 MeV,

Edelayed : 6.0 ~ 12.0 MeV- coincidence : 2 ms < te+n < 100 ms
 Multiplicity cut :100 ms window

reject pairs if there is a trigger in the preceding

IBD Candidate Event
A candidate fora neutron captured
by Gd

Background Events

Event time (S1, S2) is not satisfied

Veto hit exists

Detector Stability of Energy ScaleMeasured Spectra of IBD Prompt Signal

Backgrounds
 Backgrounds shape & rates are well understood Total 6.5% background at Far & 2.7% background at Near

Spectra & Capture Time of Delayed Signals
Neutron Capture Time by Gd

Near

Far

New Results

Observed Spectra for Prompt Signal (e+)
Neutrino energy measurement

Near

Far

Comparison of Observed Spectra

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

Expected Reactor Antineutrino Fluxes Reactor neutrino fluxPth( E )  isotopes
 fi  Ei

isotopes f  ( E )
i

i

i

i

- Pth : Reactor thermal power provided by the YG nuclear power plant- fi : Fission fraction of each isotope determined by reactor coresimulation of Westinghouse ANC- i(E) : Neutrino spectrum of each fission isotope[* P. Huber, Phys. Rev. C84, 024617 (2011)
T. Mueller et al., Phys. Rev. C83, 054615 (2011)]- Ei : Energy released per fission[* V. Kopeikin et al., Phys. Atom. Nucl. 67, 1982 (2004)]

Detection Efficiency & Systematic Uncertainties

74.17 +/-1.19

Reactor Antineutrino Disappearance A clear deficit in rate
(7.0% reduction)
 Consistent with neutrino
oscillation in the spectral
distortion

Definitive Measurement of q13

Summary RENO was the first experiment to take data with both near and
far detectors, from August 1, 2011.
 RENO has collected about 502 live days of neutrino data so far &improved systematic uncertainties and energy calibration
 RENO observed a clear disappearance of reactor antineutrinos.

 RENO measured the last, smallest mixing angle q13
sin2 2q13  0 .100  0 .010 (stat.) 0 .015 (syst.)

 There is a room to improve sys. Error (to be improved soon)

RENO-50

RENO-50
 Large q12 neutrino oscillation effects at 50 km + 5kton liquid scintillator detector
 RENO can be used as near detectors. → Precise reactor neutrino fluxes Negligible contribution from other nuclear power plants.
cos 4 q13 sin 2 2q12 sin 2  21PR  e   e   1  

2
2
2
1

sin
2
q
sin
q
cos
2

sin


sin
2

sin
2


13
12
31
21
31
21 
2






Reactor Neutrino Oscillation

Reactor Neutrino Oscillation
1.2

P(e --> e )1

L~50km experiment could bea natural extension of current
RENO q13 experiment.
(2018 ~ )

0.8
0.6

RENO

KamLAND

0.4
0.2

RENO-50

0
1

10

100
L(km)

1000

RENO-50 vs. KamLAND

RENO-50
 RENO-50 is dedicated to the YG
power plant. (negligible contribution
from the other nuclear power plants)
 RENO can be used as near detectors.
 Precise reactor neutrino fluxes :systematic error from ~3% to ~0.1%

 KamLAND uses the entire Japanese
nuclear power plants as a source.

1st m221 Maximum (L~50km) ;precise value of q12 & m221 + mass hierarchy (m231)
cos 4 q13 sin 2 2q12 sin 2  21PR  e   e   1  

2
2
2
1

sin
2
q
sin
q
cos
2

sin


sin
2

sin
2


13
12
31
21
31
21 
2




Large Deficit

sin 2q122

Ripplecos 231 sin 2  21  1 sin 231 sin 2 21
2

Precise q12

Mass Hierarchy

50 km

RENO-50
 5000 tons ultra-low-radioactivity Liquid Scintillation Detector
RENO
RENO-50
5.8 m

8.8 m

500 10” OD PMTs

5.4 m
20 m

25 m

8.4 m

LAB (5 kton)
6000 10” PMTs

20 m

KamLAND

25 m

Water

Site Survey for RENO-50

MC Simulation for RENO-50
 Energy Resolution

 Also GloBES study is under way

MC Study of Mass Hierarchy at RENO-50
 Bin size effect of determining mass hierarchy At least 3% energy resolution is needed to distinguish NH and IH(@ ~5 MeV : 12 bin/MeV)
E
: 6%
E

E
: 6%
E

50 bin/MeV

12 bin/MeV

EE

12 bin/MeV

E

: 3%

E

12 bin/MeV: 2%

MC Study of Mass Hierarchy at RENO-50
 χ2 calculation test□ χ2 calculation test RENO-50 expects to observe ~1500 events / year.
- Include oscillation effects and assume 70% detection efficiency.
□ Generate for NH and calculate χ2 based on
hypotheses of NH or IH.
- χ2 value decreases rapidly with energy resolution.
- 3σ determination : 60000 events (40 years) for RENO-50.
[10 years for a 20 kton detector]

 Conclusion□ A large ( > 20 kton) detector with 3% energy resolution is needed(25% PMT coverage) to determine neutrino mass hierarchy.
- 10 years of data taking.
- Modular detector components necessary because of~25m attenuation length.
□ RENO-50 needs an alternative solution for the mass hierarchy.
□ The solution will be reported soon….

RENO-50 vs. KamLAND
Oscillation
Reduction

Reactor
Detector
Neutrino Flux
Size

Syst. Erroron  Flux

Error onsin2q12RENO-50(50 km)80%

13×6×0[6 reactors]

5 kton~ 0.3%~1%

KamLAND(180 km)

40%

53×0
[53 reactors]

1 kton3%

5.4%

Figure of
Merit

×2

×1.5

×5

×10

(50 km / 180 km)2 ≈ 13

J-PARC neutrino beam
Dr. Okamura & Prof. Hagiwara

Physics with RENO-50 (1) Precise measurement of q12 and m221

 sin 2 q12~ 1.0%1s  in a year2
sin q12(← 5.4%)

m 2 21m 2 21~ 1.0%1s  in 2~3 years(← 2.6%)

 Determination of mass hierarchy (sign of m231 or m232)- Quite challenging : requires extremely good energy resolution- Plan B : an additional 1000 ton detector at ~10 km(L : 300 m + 1.4 km + 10 km + 50 km)

 Neutrino burst from a Supernova in our Galaxy- ~1500 events (@8 kpc)
- A long-term neutrino telescopePhysics with RENO-50 (2) Geo-neutrinos : ~ 300 geo-neutrinos for 5 years- Study the heat generation mechanism inside the Earth Solar neutrinos : with ultra low radioacitivity- Matter effects on neutrino oscillation- Probe the center of the Sun and test the solar models

 Reactor physics : non-proliferation
 Detection of J-PARC beam : ~120 events/year Test of non-standard physics : sterile/mass varying neutrinos

Physics with RENO-50 (3) Search for neutrinoless double beta decay

RENO-50
Water

20 m

25 m

LAB (5 kton)

3000 10” PMTs

20 m
25 m

Closing Remarks
 RENO, the first Korean neutrino detector, observed a clear
disappearance of reactor antineutrinos, and performed a definitive
measurement of q13 with both near and far detectors in operation.
 A surprisingly large value of q13 will strongly promote the next
round of neutrino experiments to find the CP phase and determine
the mass hierarchy.
 RENO will continue data-taking for next 3~4 more years, reachingits sensitivity limit, in order to obtain a precise measurement of q13.
 Korean reactors can be used as an intense neutrino source tostudy the neutrino properties. RENO-50, a multi-purpose neutrino
detector, is pursued to perform high-precision measurements of q12
and m221, determine the mass hierarchy, and detect neutrinos fromthe astrophysical sources.

RENO-50 Workshop @Seoul

http://home.kias.re.kr/MKG/h/reno50/
When: June 13 – 14, 2013

Where: Seoul National University, Seoul, Korea

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