1. Reactor Neutrino Experiments Institute of High Energy Physics
Yifang Wang
Institute of High Energy Physics
Dec. 19, 2013, LONDON

2. A Long, Successful History
Direct observation(50’s): Reines
Oscillation：
Early searches(70’s-90’s):
Reines, ILL, Bugey, … Palo Verde, Chooz
Determination of q12(90’s-00’s):
KamLAND
Discovery of q13 (00’s-10’s): :
Daya Bay, Double Chooz，RENO
Neutrino magnetic moments (90’s-00’s):
Texono, MUNU
Mass hierarchy(10’s-20’s):
JUNO, RENO-50
Sterile neutrinos(10’s):
Nucifer, Stereo, Solid …
2018/4/19

3. A Long, Successful History
Direct observation(50’s): Reines
Oscillation：
Early searches(70’s-90’s):
Reines, ILL, Bugey, … Palo Verde, Chooz
Determination of q12(90’s-00’s):
KamLAND
Discovery of q13 (00’s-10’s): :
Daya Bay, Double Chooz，RENO
Neutrino magnetic moments (90’s-00’s):
Texono, MUNU
Mass hierarchy(10’s-20’s):
JUNO, RENO-50
Sterile neutrinos(10’s):
Nucifer, Stereo, Solid …
2018/4/19

4. Experiments with neutrinos from reactors
Huge production yield：6 /s @ 3 GW
Powerful background rejection capability：
Neutrino energy:
10-40 keV
1.8 MeV: Threshold
2018/4/19

5. Reactor Experiments: comparing observed/expected neutrinos
Precision of past experiments，typically 3-6%
Reactor power: ~ 1%
Spectrum: ~ 0.3%
Fission rate: 2%
Backgrounds: ~1-3%
Target mass: ~1-2%
Efficiency: ~ 2-3%
Pee  1  sin22q13sin2 (1.27Dm213L/E) 
cos4q13sin22q12sin2 (1.27Dm212L/E)
2018/4/19

6. q13: Three on-going experiments
Power
(GW)
Baseline(m)
Near/Far
Detector(t)
Overburden (MWE)
Designed Sensitivity
(90%CL)
Daya Bay
17.4
470/576/1650
40//40/80
250/265/860
~ 0.008
Double Chooz
8.5
400/1050
8.2/8.2
120/300
~ 0.03
Reno
16.5
409/1444
16/16
120/450
~ 0.02
Daya Bay
Double Chooz
Reno
Far Detector
Near Detector

7. Detectors Neutrino detector(s) in a water pool
Water for shielding backgrounds
Water for stabilizing running conditions
Water Cherenkov for muon veto
RPC/plastic scintillator at the top of the water pool for muon veto
Three-zone neutrino detector:
Target: Gd-loaded LS
~ 10-20t for neutrino
g-catcher: normal LS
~ 10-20t for energy containment
Buffer shielding: oil
~ 20-40t for shielding
optical reflectors
Light collection
PMTs
Coverage
P.E. yield
P.E. yield/Coverage
target mass
Daya Bay
"
~6%
163 pe/MeV
1.77
26%
RENO
"
~15%
230 pe/MeV 1
14.5%
Double Chooz
"
~16%
200 pe/MeV
0.81 7%
2018/4/19

8. Event Signature and Backgrounds
Prompt: e+, MeV,
Delayed: n, Gd
Capture time: 28 ms in 0.1% Gd-LS
Backgrounds
Uncorrelated: random coincidence of gg, gn or nn
g from U/Th/K/Rn/Co… in LS, SS, PMT, Rock, …
n from a-n, m-capture, m-spallation in LS, water & rock
Correlated:
Fast neutrons: n scattering - n capture
8He/9Li: b decay -n capture
Am-C source: g rays - n capture
a-n: 13C(α,n)16O
2018/4/19

9. Daya Bay Experiment: Layout
Redundancy !!!
Relative measurement to cancel Corr. Syst. Err.
2 near sites, 1 far site
Multiple AD modules at each site to reduce Uncorr. Syst. Err.
Far: 4 modules，near: 2 modules
Multiple muon detectors to reduce veto eff. uncertainties
Water Cherenkov： 2 layers
RPC： 4 layers at the top + telescopes
Cross check; Reduce errors by 1/N
2018/4/19

10. Daya Bay：Data taking & analysis status
Two detector comparison [ ]
90 days of data, Daya Bay near only
NIM A 685 (2012), 78-97
First oscillation analysis [1203:1669]
55 days of data, 6 ADs near+far
PRL 108 (2012),
Improved oscillation analysis [ ]
139 days of data, 6 ADs near+far
Chin.Phys. C 37 (2013),
Spectral Analysis
217 days complete 6 AD period
55% more statistics than CPC result
Submitted to PRL, arXiv:
4/19/2018

11. Daya Bay：First Results
R = ±0.011 (stat) ±0.004 (syst)
Sin22q13 =  0.016(stat)  0.005(syst)
c2/NDF = 4.26/4, σ for non-zero θ13
R = ±0.007 (stat) ±0.003 (syst)
Sin22q13 =  0.010(stat)  0.005(syst)
c2/NDF = 3.4/4, 7.7 σ for non-zero θ13
F.P. An et al., Phys. Rev. Lett. 108, (2012)
F.P. An et al., Chin. Phys.C 37(2013)
2018/4/19

12. ~  2 More statistics: Summary
Consistent rates for side-by-side detectors
Expected： AD1/AD2 = 0.981
Measured：AD1/AD2 = 0.004(stat) 0.002(syst)

13. Rate-Only Oscillation Results
sin22θ13 = ± 0.009
Uncertainty reduced by statistics of complete 6 AD data period
Standard approach: χ2/NDoF = 0.48/4
|Δm2ee| constrained by MINOS result for |Δm2μμ|
Far vs. near relative measurement: absolute rate not constrained
Consistent results from independent analyses, different reactor flux models
4/19/2018
arXiv:

14. Rate+Spectrum analysis
Each energy bin is an independent oscillation measurement, but requires detailed understanding of detector energy response：
Scintillator response
Electron  calibration
Gamma & positron response  connect to electrons through MC
Readout electronics
Slow scintillation component missed at high energies
Charge collection efficiency decreases with visible light

15. Building Non-Linearity Models
Method 1
No constraints on scintillation model from bench data
Any combination of parameterizations for scintillator and electronics
All parameters determined by simultaneous t to 12B and gamma data
Cross-check with remaining 3 continuous + spectra
Method 2
Semi-empirical model based on Birks' law for scintillation response
Birks constant and Cherenkov contribution constrained by bench measurements
Electronics response from quadratic to gamma data
Cross-check with all 4 continuous + spectra
Method 3
Semi-empirical model for scintillation response
Birks constant constrained by bench measurements
Cherenkov contribution and electronics from exponential to all 4 + spectra
Cross-check with gamma data

16. Final Positron Energy Non-Linearity Response
Several validated models
Constructed based on different parameterizations/weighting of data constraints
5 Models with minimum correlations selected, consistent within 1.5%
Uncertainty is conservatively estimated by the curves+uncertainties in 68% C.L.
4/19/2018

17. Prompt IBD spectra (~En)
4/19/2018

18. Pure Spectral Analysis
θ13 = 0 can be excluded at > 3σ from spectral information alone

19. Rate+Spectra Oscillation Results
arXiv:

20. RENO Status A B C Near Far C (~700 days) : Shape+rate analysis
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
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]
From Soo-Bong Kim

21. RENO Results First result in April 2, 2012.
A new result reported in March, 2013.
Reduced c2 = 1.21
For details, see Seon-Hee Seo’s talk at NeuTel 2013

22. Double Chooz: many results

24. Reactor Rate Modulation(RRM) method

25. Global Comparison of θ13 Measurements
Be careful to take the average:
Correlated errors
Error estimate
The three reactor experiments will work together to report results in a coherent way, and probably can report a combined result.
4/19/2018
Spectral Measurement of Antineutrino Oscillation at Daya Bay

26. Future prospects: Daya Bay
Sensitivity still dominated by statistics
Statistics contribute 73% (65%) to total uncertainty in sin2 2θ13 (|Δm2ee| )
Major systematics:
θ13 : Reactor model, relative+absolute energy and relative efficiencies
|Δm2ee| : Relative energy model, relative efficiencies and backgrounds
Precision of mass splitting measurement closing in on results from μ flavor sector
4/19/2018

27. Daya Bay Onsite Progress
Final two detectors installed, operating since Oct
Full 4π detector calibration
in Sep
EH2
EH3
4/19/2018

28. RENO’s Projected Sensitivity of q13
(7 % precision)
ssyst =0.015
Goals
- sin22q13 to 7% precision
- direct measurement of Dm231
- precise measurement of reactor neutrino flux and spectrum
- study for reactor anomaly and sterile neutrinos
From Soo-Bong Kim

29. Double Chooz Near detector in construction till Spring 2014.
The first result of the full experiment will be available at the end of 2014, towards a final precision of 10%.
From Herve de Kerret

30. Next Step: Mass Hierarchy
Daya Bay
Huizhou
Lufeng
Yangjiang
Taishan
Status
running
planned
approved
Construction
construction
power/GW
17.4
18.4
Daya Bay
60 km JUNO
Previous site
Lufeng
Huizhou
Daya Bay
Current site
Hong Kong
Before 2020：
Yangjiang 17.4GW + Taishan19.9 GW
= 27.3 GW
Taishan
Yangjiang

31. The plan: a large LS detector
LS volume:  20 for more mass & statistics
light(PE)  5 for resolution
Muon detector
Steel Tank
20 kt LS
Water seal
20kt water
Acrylic tank：F34.5m
Stainless Steel tank ：F37.5m
6kt MO
~ ” PMTs
coverage: ~80%
” VETO PMTs

32. Physics Reach Thanks to a large θ13 Mass hierarchy
Y.F. Li et al., arXiv:
Mass hierarchy
Precision measurement of mixing parameters
Supernova neutrinos
Geoneutrinos
Sterile neutrinos ……
Current
Daya Bay II
Dm212 3%
0.6%
Dm223 5%
sin2q12
0.7%
sin2q23
N/A
sin2q13
10% 4%
~ 15%
For 6 years，mass hierarchy cab be determined at 4 level, if Δm2mm can be determined at 1% level
Detector size: 20kt
Energy resolution: 3%/E
Thermal power: 36 GW
2018/4/19

33. IBD Signal Signal: LS without Gd-loading for
Better attenuation length  resolution
Lower irreducible accidental backgrounds from LS, important for a larger detector:
With Gd: ~ g/g
Without Gd: ~ g/g
Less risk
Longer capture time & lower energy the capture signal  more accidental backgrounds
Estimated IBD rate: ~40/day
t ~ 200 ms

34. Backgrounds Summary Assumptions Overburden is 700m
Em ~ 211 GeV, Rm ~ 3.8 Hz
Single rates from LS and PMT are 5Hz, respectively
Good muon tracking
Similar muon efficiency as DYB
Daya Bay
Daya Bay II
Mass (ton) 20
20,000
Em (GeV)
~57
~211
Lm (m)
~1.3
~ 23
Rm (Hz)
~21
~3.8
Rsingles (Hz)
~50
~10
DYB EH1
DYB II
Techniques used for DYB II detector
Accidentals
~1.4%
~10%
Low PMT radioactivity; LS purification;
prompt-delayed distance cut
Fast neutron
~0.1%
~0.4%
High muon detection efficiency (similar as DYB)
9Li/8He
~0.8%
Muon tracking;
If good track, distance to muon track cut (<5m) and veto 2s;
If shower muon, full volume veto 2s

35. MC example：Energy Resolution
MC based on DYB MC (tuned to data), except
JUNO Geometry and 80% photocathode coverage
SBA PMT: maxQE from 25% -> 35%
+13% light (add PPO, …)
LS Atten. length (1m-tube
from 15m = absoption 24m + Raylay scattering 40 m
to 20 m = absorption 40 m + Raylay scattering 40m
Uniformly Distributed Events R3
After vertex-dep. correction

36. Detector design Several detector options: Design is underway
Acrylic ball + unistruct for PMT
Steel ball + acrylic blocks
Steel ball + acrylic walls + Balloon …
Design is underway
Prototype will be started by the end of year
Final decision:
2018/4/19

37. Example: Acrylic tank
Unistruct for PMT mounting  Same structure for Central Detector and VETO
Oil buffer  Water buffer  Cheap
Technology from construction industry
15% density difference leads to a maximum pressure of ~6m in air 
A normal aquarium
Zhujiang City Building
Ball conference : 39 m

38. High QE MCP-PMT Design principle verified Technical feasibility proved
Many prototypes：
QE ~ 30%
SPE P/V ~ 2
Noise，After-Pulse… in good shape
Quality improvement underway
Gain=6.25*10E6
@ P/V=1.47
Single P.E.
Sum
Reflective photocathode
Transmitted photocathode

39. Site selection Site is determined, configuration is finalized
A vertical shaft(600 m) + sloped tunnel(1300m)
Overburden: ~ 700 m

40. Geological survey completed
One 600m bore holes + four other holes + geophysical studies + ….
Good rock:
no water leak
high quality(complete piece), …
Rock temperature: 31 oC

41. Status of the project Conceptual design & R&D plan approved in China
Paper work to get construction permission underway
Civil construction:
Feasibility study report completed
Cost and schedule understood
Detailed design underway
2018/4/19

42. Brief schedule Collaboration will be established soon
Civil preparation：
Civil construction：
Detector R&D：
Detector component production：
PMT production：
Detector assembly & installation：
Filling & data taking：2020
Collaboration will be established soon
Welcome collaborators
2018/4/19

43. Proposal for RENO-50 Soo-Bong Kim (KNRC, Seoul National University)
“International Workshop on RENO-50, June 13-14, 2013”

44. 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 : - High-precision measurement of q12 and Dm Determination of neutrino mass hierarchy 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 : ~ 2018 : Facility and detector construction ~ : Operation and experiment

45. Conceptual Design of RENO-50
30 m
32 m
LS (18 kton)
” PMTs (67%)
Mineral Oil
37 m
Water
” OD PMTs

46. Reactor neutrino anomaly
By a new flux calculation, there may exist a reactor neutrino flux deficit: 0.943± A 3s effect ?
Later confirm by other calculations
Oscillation with sterile neutrinos ?
Other experimental “hints”: LSND, MiniBooNE, Gallex…
Global fit of all “hints”: severe tensions
Cosmological bounds: not so favored
New analysis: different opinions
T.A. Mueller et al., PRC83:054615,2011
P. Huber et al., PRC84:024617,2011.
C. Zhang et al.,
arXiv:
A.C. Hayes et al.,
arXiv:
D. 2012
G. Mention et al., PRD83(2011)073006

47. Solution: experiments
Radioactive sources: CeLAND(144Ce in KamLAND), SoX(51Cr in Borexino),…
Accelerator beams: IsoDAR, Icarus/Nessie, nuSTORM…
Reactors: Nucifer, Stereo, Solid,…
New measurements of b-spectrum from U & Pu(Munich)
Reactor core
7 m
Error bars dominated by subtraction of accidental background
Nucifer
Figures from T. Lasserre
Will be upgraded to reduce backgrounds
2018/4/19

48. Summary Reactor neutrinos are powerful and well understood
Recently very successful on q12, q13, …
Precision on Sin22q13 will be significantly improved in the next few years, up to ~ 3-4%
Reactor neutrinos will play important roles on:
Mass hierarchy
Precision measurement of 3/6 mixing parameters up to < ~1% level  unitarity test of the mixing matrix
Sterile neutrinos
Neutrino properties: magnetic moments, coherent scattering, …
2018/4/19