Current Results & Future Perspectives
from Reactor Neutrino Experiments
Soo-Bong Kim (KNRC, Seoul National University)“Tsukuba Global Science Week (TGSW2014), Tsukuba, Sep. 28-30, 2014”

Reactor 13 Experiments
RENO at Yonggwang, Korea

Daya Bay at Daya Bay, China

Double Chooz at Chooz, France13 Reactor Neutrino Detectors

MOLSGd-LS

H2O

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

RENO Experimental Set-up
120 m.w.e.
Near Detector

Far Detector
450 m.w.e.

RENO Status

 A (220 days) : First 13 result[11 Aug, 2011~26 Mar, 2012]
PRL 108, 191802 (2012)

Near Detector
DAQ Efficiency

 Data taking began on Aug. 1, 2011 withboth near and far detectors.
(DAQ efficiency : ~95%)

 Total observed reactor neutrino events asof today : ~ 1.5M (Near), ~ 0.15M (Far)→ Absolute reactor neutrino flux
measurement in progress[reactor anomaly & sterile neutrinos]

0.6

A

0.2

2011 Jan 2012

Jan 2013

Jan 2014

Now

Far Detector
DAQ Efficiency

Shape+rate analysis (in progress)[11 Aug, 2011~31 Dec, 2013]

0.8

0.4

 B (403 days) : Improved 13 result[11 Aug, 2011~13 Oct, 2012]
NuTel 2013, TAUP 2013, WIN 2013

 C (~800 days) : New 13 result

110.8

B

0.6

C0.4(new results)

0.2

2011 Jan 2012

Jan 2013

Jan 2014Detection of Reactor Antineutrinos(prompt signal)γ(0.511MeV)e-(delayed signal)~180 ms+ p  D +  (2.2 MeV)
~28 ms
(0.1% Gd) + Gd  Gd + ‘s (8 MeV) Neutrino energy measurementγ(0.511MeV)e+νeprompt signal

pn
Delayed signal

30μsγ

γ

 E ~ 8MeVGdγγNew RENO Results■ ~800 days of data
■ New measured value of 13from rate-only analysis(Neutrino 2014)■ Shape analysis in progress■ Observation of a new reactor neutrino component at 5 MeV■ Results of reactor neutrinos with neutron capture on H

(Significant improvement from Neutrino 2014)

Neutron Capture by Gd

Measured Spectra of IBD Prompt Signal

Bkg.: 3.1 %Near Live time = 761.11 days
# of IBD candidate = 457,176# of background = 14,165 (3.1 %)Bkg.: 8.1 %Far Live time = 794.72 days
# of IBD candidate = 53,632# of background = 4366 (8.1 %)Observed Daily Averaged IBD Rate
IBD rate ( /day)

1000

Expected with no oscillation
Expected with oscillation (best fit)

500

preliminary

Near Detector
10050Far Detector
02011 Aug2012 Jan2012 July

2013 Jan2013 July

2014 Jan Good agreement with observed rate and prediction.
 Accurate measurement of thermal power by reactor neutrinos

Observed vs. Expected IBD Rates

sin2213 = 0.101|Δm312| = 2.32 x 10-3 eV2- Good agreement between observed rate & prediction- Indication of correct background subtraction

New 13 Measurement by Rate-only Analysis(Preliminary)sin 2 2θ13  0.101  0.008(stat.)  0.010(syst.)
Uncertainties (%)

0.1

Statistics (near)(far)
Isotope fraction0.2

0.3

0.5

0.6(0.15%)(0.43%)(0.28%)

Thermal power(0.20%)

Detection efficiency(0.20%)

Backgrounds (near)(far)(0.21%)

sin 2 2θ13  0.113  0.023
 0.100  0.016
 0.101  0.013

0.4(0.50%)

4.9 s (Neutrino 2012)
6.3 s (TAUP/WIN 2013)
7.8 s (Neutrino 2014)

Why n-H IBD Analysis?

Motivation:
1. Independent measurement of 13 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.

IBD Sample with n-Hpreliminaryn-H IBD Event Vertex Distribution

target-catcher

NearFarLive time(day)379.663384.473

IBD Candidate

249,799

54,277

IBD( /day)

619.91667.823

Accidental ( /day)

25.16±0.4268.90±0.35

Fast Neutron( /day)

5.62±0.30

1.30±0.08

LiHe( /day)

9.87±1.48

3.19±0.37

Results from n-H IBD sample
Very preliminary
Rate-only result(B data set, ~400 days)sin 2θ13  0.103  0.014(stat.)  0.014(syst.)
2(Neutrino 2014) sin 2 2θ13  0.095  0.015(stat.)  0.025(syst.)← Removed a soft neutron backgroundand reduced the uncertainty of the accidental background
preliminary

preliminary

Near Detector

Far Detector

Reactor Neutrino Oscillations
Short Baselinecos 2 𝜃12 Δ𝑚221

Long Baseline[Nunokawa & Parke (2005)]

Energy Calibration from -ray Sources

Energy Calibration from B12 b-decays
Near detector

Far detector

B12 Energy Spectrum (Near & Far)Observation of a New Reactor Neutrino
Component at 5 MeV2.18±0.10%

1.78±0.30%

Fraction of 5 MeV excess (%) to expected flux [2011 Huber+Mueller]Near : 2.18 ± 0.40 (experimental) ± 0.49 (expected shape error)
Far : 1.78 ± 0.71 (experimental) ± 0.49 (expected shape error)

The 5 MeV Excess Seen at Double-Chooz
and Daya Bay

Daya Bay, ICHEP 2014

Double-Chooz, Neutrino 2014

Correlation of 5 MeV Excess with Reactor PowerCorrelation of 5 MeV Excess with Reactor Power
5 MeV excess
has a clear
correlation
with reactor
thermal power !
two or threereactors are off

All the six
reactors are on

A new reactor neutrino
component !!

Far/Near Shape Analysis for Dmee2

Reactor Neutrino Disappearance on L/E

RENO’s Projected Sensitivity of 13
Neutrino 2014 sin

2213  0.101  0.008(stat.)  0.010(syst.)(~800 days) 0.101  0.013 (7.8 s)(13 % precision)

 0.007 (14 s) (in 3 years)(7 % precision)

2012. 4 5 years of data : ±7%
2013. 32013. 92014. 6

- stat. error : ±0.008 → ±0.005- syst. error : ±0.010 → ±0.005- shape information → ±5%(7 % precision)

A Brief History of 13 from Reactor Experiments
DC: 97 days
R+S

[1112.6353]

DB: 49 days
RENO: 222 days
DC: 228 days
R+S
DB: 139 days
DC: n-H
R+S[1203.1669][1204.0626][1207.6632]

RENO: 403 days

[NuTel2013][1305.2734]

DC: RRM analysis
R+S
DB: 190 days
R+S
RENO: 403 days

DB: 190 days n-H
DC: 469 days
DB: 563 days
RENO: 795 days
384 days n-H
RENO 384 days n-H[1210.6327][1301.2948][1310.6732][TAUP2013][Moriond2014][n 2014][n 2014][n 2014][n 2014][NOW 2014]13 from Reactor and Accelerator Experiments
First hint of δCP combining
Reactor and Accelerator data
Best overlap is forNormal hierarchy & δCP = - π/2
Is Nature very kind to us?
Are we very lucky?
Is CP violated maximally?

Strong motivation foranti-neutrino run and precise
measurement of θ13
Courtesy C. Walter (T2K Collaboration)
Talk at Neutrino 2014

Summary We observed a new reactor component at 5 MeV. (3.6 s)
 New measurement of 13 by rate-only analysis

sin 2 2θ13  0.101  0.008(stat)  0.010(syst)(preliminary) Shape analysis for Dm2 in progress… (stay tuned) First result on n-H IBD analysis

sin 2 2θ13  0.103  0.014(stat)  0.014(syst)(very preliminary) sin2(213) to 7% accuracy within 3 years→ will provide the first glimpse of CP.
If accelerator results are combined.

Overview of RENO-50
 RENO-50 : An underground detector consisting of 18 kton ultralow-radioactivity liquid scintillator & 15,000 20” PMTs, at 50 km awayfrom the Hanbit(Yonggwang) nuclear power plant Goals : - Determination of neutrino mass hierarchy- High-precision measurement of 12, Dm221 and Dm231- 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 : 2014 ~ 2019 : Facility and detector construction
2020 ~: Operation and experimentNear Detector

Far Detector(NEAR Detector)(FAR Detector)

RENO-50
10 kton LS Detector~47 km from YG reactors
Mt. Guemseong (450 m)~900 m.w.e. overburden2012 Particle Data Book

sin212 = 0.312±0.017 (±5.4%)(±2.8%)(±2.7%)∆m212 / |∆m31(32)2| ≈ 0.03(±3.1%)(+5.2-3.4%)(±13.3%)

 Precise measurement of 12, Dm221 and Dm232

 sin 2 12
 1.0%1s 2sin 12(← 5.4%)

Dm 2 21
Dm 212

 1.0%1s (← 2.7%)

Dm 2 32
Dm 322

 1.0%1s (← 5.2%)

Additional Physics with RENO-50
 Neutrino burst from a Supernova in our Galaxy- ~5,600 events (@8 kpc) (* NC tag from 15 MeV deexcitation )- 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 likeKamLAND-Zen

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

* See talks by Yuji Tacheuchi and Takuya Okudaira Only neutrino mass is unknown in elementary particle physics.
 Detection of neutrino decay ⇒ neutrino mass itself if combined with Dm2 measured byneutrino oscillation experiments.

n3W

,mn2


n n  
322m 32  m 22 Dm 23
E 
2m 32m 32Using Dm 23
 ( 2.43  0.09)  10  3 eV2E  10～25 meV at n 3 rest frame.
(Far - Infrared region   50～125 m ) As the neutrino lifetime is very long, we need use cosmic background neutrinos
to observe the neutrino decay. Observation of neutrino decay ⇒ a discovery of thecosmic background neutrinos predicted by cosmology.

Cosmic Infrared Background :~105 higher than neutrino decay
signal expected from a lifetime of
1.5 x 1017year(Left-Right symmetric model).
10-hour running witha telescope with 20cm diameter,a viewing angle of 0.1 degrees
and 100% detection efficiency( Satellite Experiment )● Need the energy resolution better than 2%.
● Can observe the ν3 decay with a mass of 50meV, and a lifetime of 1.5 x 1017year (present lifetime limit: 3 x 1012year)● A rocket experiment in 2017 as a preparatory trial for the satellite experiment→ Improve lifetime limit by two orders of magnitude ( ~1014year).
● R&D of superconducting tunnel junction (STJ) detector

Thanks for your attention!

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

With 5 MeV excess

Reactor Neutrino Oscillations at 50 km
Neutrino mass hierarchy (sign of Dm231)+precise values of 12, Dm221 & Dm231

Precise Dm221
Large Deficit

sin 2122Ripplecos 2D31 sin 2 D 21  1 sin 2D31 sin 2D 21
2Precise 12

Mass Hierarchy