reactor neutrino experiments - miami
TRANSCRIPT
Reactor Neutrino Experiments
Ke Han Yale University
December 21, 2014
20kt LS (undoped)
Acrylic tank: Φ34.5mStainless Steel tank: Φ37.5m
Fireball
Vacuumpump
Feathers andfoam rubber
Vacuumline
Vacuumtank
Suspendeddetector
Back fill
Buried signal linefor triggering release
Nuclear explosive
40 m
30 m
Miami 2014 3 Ke Han, Yale University
“El Monstro” – First design to detect (anti) neutrinos
Suspendeddetector
n → p+ e− + ν̄e
ν̄e + p → e++n
• Reactor anti-νe Inverse beta decay + neutron capture
Neutrino Discovery by Reines and Cowan in 1956
Hanford, WA, 1953, 300 L Savannah River, SC, 1956, ~5000 L
At the time Cowan and I got into the act, a “big” detector was only a liter or so in volume – Reines, 1995
νeνe
Incidentantineutrino
Positronannihilation
Inverse beta
decay
Gamma rays
Gamma rays
e+
n
Neutron capture
Liquid scintillator and cadmium
ν̄e + p → e++n
Miami 2014 Ke Han, Yale University 4
Neutrino Oscillation -- two flavor scenario
| ( )〉 = − cos | 〉+ − sin | 〉
L or t
→ ( ) = − sin sin
( )Survival Probability:
1 5 10 50 100 500
0.0
0.2
0.4
0.6
0.8
1.0
Distance [km]
Surv
ival
Pro
babi
lity
LE
� 1Δm2
LE
� 1Δm2
LE
≈ 1Δm2
sin2(2θ0) = 0.84Eν = 5MeV
Δm2 ≈ 7×10−5eV2• •
•
Miami 2014 Ke Han, Yale University 6
• 1 kton liquid scintillator detector to measure reactor anti-νe disappearance.
• Confirmed the deficits expected from ν oscillation
• Observed the periodic feature of the anti-νe survival probability
KamLAND – reactor neutrino disappearance
Miami 2014 Ke Han, Yale University 7
• 1 kton liquid scintillator detector to measure reactor anti-νe disappearance.
• Confirmed the deficits expected from ν oscillation
• Observed the periodic feature of the anti-νe survival probability
KamLAND -- oscillation
(km/MeV)eν
/E0L
20 30 40 50 60 70 80 90 100 110
Surv
ival
Pro
babi
lity
0
0.2
0.4
0.6
0.8
1
eνData - BG - Geo best-fit oscillationν3-
best-fit oscillationν2-
Miami 2014 Ke Han, Yale University 8
Neutrino mixing – 3 flavor
Short Baseline Reactor LBL Accelerator
⎛⎝ νe
νμντ
⎞⎠=
⎛⎝−
⎞⎠⎛⎝
−
− −
⎞⎠⎛⎝
−
⎞⎠
ci j = cos(i j), si j = sin(i j)
⎛⎝ ν1
ν2ν3
⎞⎠
oscillation frequency L/E →Δm2
ampl
itude
of
osci
llatio
n θ
Δm223 = ~2.4 x 10-3 eV2
Δm212 =~7.6 x 10-5 eV2
Pee ≈1− sin2 2θ13 sin
2 Δm312L
4Eν
⎛
⎝ ⎜
⎞
⎠ ⎟ − cos4 θ13 sin
2 2θ12 sin2 Δm21
2L
4Eν
⎛
⎝ ⎜
⎞
⎠ ⎟
Miami 2014 Ke Han, Yale University 9
Measuring θ13 with Reactor Experiments
far
νe
distance L ~ 1.5 km
νe,x νe,x
Absolute Reactor FluxLargest uncertainty in previous measurements
Relative MeasurementRemoves absolute uncertainties!
θ13
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
0.1 1 10 100
N osc/N
no_o
sc
Baseline (km)
Δm213≈ Δm2
23
detector 1 detector 2
Near vs Far Detector
near
far/near νe ratio target mass distances efficiency oscillation deficit
νeνe νe
Miami 2014 Ke Han, Yale University 10
Daya Bay – Observation of anti-ve Disappearance N
dete
cted
/Nex
pect
ed
Based on 55 days of data with 6 ADs, discovered disappearance of reactor νe at short baseline. [PRL 108, 171803]
Obtained the most precise value of θ13:
sin22θ13 = 0.089 ± 0.010 ± 0.005 [CPC 37, 011001]
sin22θ13 > 0
• • •
Miami 2014 Ke Han, Yale University 11
RENO
RENO and Double Chooz
2 4 6 8 10 12Energy (MeV)
Even
ts/0.
5 MeV
0102030
2 4 6 8 10 12Energy (MeV)
−100
−50
050
0.60.8
11.21.4
200
400
600
800
1000
1200
1400
Even
ts/0.
5 MeV
(Data/
pred
icted)
(Data/
pred
icted)
(0.5
MeV
)
0
500
1000
Far detectorNear detector
Prompt energy (MeV)
00
10
5 10
Prompt energy (MeV)0 5 10
20
30
40
Entries/
0.25
MeV
Entries/
0.25
MeV
Fast neutronAccidental9Li/8He
Double Chooz
Miami 2014 Ke Han, Yale University 12
Reactor Neutrinos – Next Steps
Daya Bay
Double Chooz
RENO
KamLAND
Is the 3-ν picture complete? Are there more than 3 neutrinos?
What is the flux of reactor antineutrinos?
What is the mass hierarchy?
•
•
• •
Miami 2014 Ke Han, Yale University 14
Oscillation parameter precision measurement
Proposed Projects: JUNO and RENO-50
RENO-50 JUNO
Miami 2014 Ke Han, Yale University 15
Mass Hierarchy
JUNO
Miami 2014 Ke Han, Yale University 16
m2
0
solar~7.6×10–5eV2
atmospheric~2.5×10–3eV2
atmospheric~2.5×10–3eV2
m12
m22
m32
m2
0
m22
m12
m32
νe
νμ ντ
? ?
solar~7.6×10–5eV2
Mass Hierarchy Sensitivity
JUNO
• Reactor antineutrino anomaly: deficit in the observed reactor flux
• Among other hints of sterile neutrino(s): – LSND – MiniBoone – Gallium – Neff in cosmology
Reactor neutrino – very short baseline ~10 m
Distance to reactor (m)Bu
gey-
4 ROV
NO
91
Buge
y-3
Buge
y-3
Buge
y-3
Goe
sgen
-I
Goe
sgen
-II
Goe
sgen
-III
ILL
Kras
noya
rsk-
I
Kras
noya
rsk-
II
Kras
noya
rsk-
III
SRP-
ISR
P-II
ROV
NO
88-1
IRO
VN
O88
-2I
ROV
NO
88-1
S
ROV
NO
88-2
S
ROV
NO
88-3
S
Palo
Ver
de
CHO
OZ
Dou
ble C
HO
OZ
0.750.8
0.850.9
0.951
1.051.1
1.15
𝑁O
BS/(
𝑁ex
p) p
red,
new
100 103
Miami 2014 Ke Han, Yale University 17
• Spectral deviation of data vs. prediction in 4-6 MeV
• Recent ab-initio calculation provides a possible explanation involving decays from prominent fission daughter isotopes. Dwyer, Langford: arXiv:1407.1281
Reactor neutrino – very short baseline ~10 m
41.4/24
0.015
Miami 2014 Ke Han, Yale University 18
PROSPECT- A Precision Reactor Oscillation and Spectrum Experiment
•
• •
•
• •
•
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U.S. High Power Research Reactor Facilities
Site Power Duty Cycle
Near Baseline
Average Near Flux
Far Baseline
Average Far Flux
NIST 20 MWth 68% 5.3m 1 17.0m 1
HFIR 85 MWth 41% 7.9m 1.1 17.9m 2.3
ATR 110 MWth 68% 10.1m 1.5 18.8m 4.5
Rel
ativ
e Po
wer
(ar
b.)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
x (m)-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6
y (m
)
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6(a)
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
Rel
ativ
e Po
wer
(ar
b.)
0.0
0.2
0.4
0.6
0.8
1.0(e)
Rel
ativ
e Po
wer
(ar
b.)
0.0
0.2
0.4
0.6
0.8
1.0
x (m)-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6
y (m
)
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6(c)
• •
• •
Miami 2014 Ke Han, Yale University 21
Detector Development– Segmentation Concept
• 2D segmentation provides 3D position resolution, reasonable channel count, and space efficiency
• Need for minimal dead material guides design – Goal: < 2% dead material (>15% for Bugey3)
• “Unit cell” built from reflecting separators and longitudinal posts – allows excellent calibration access
• Sealed PMT modules couple via acrylic light guides
~14cm
~100cm
Li-doped LS
Light Guide
Miami 2014 Ke Han, Yale University 23
Detector Development – Separators and LS
Li-loaded Scintillator: • Formulation methods identified
• Several candidates with good scintillation light yield, capture timing, PSD, compatibility
Reflecting segment system • Fabrication method identified
• Testing multiple material options
Miami 2014 Ke Han, Yale University 24
• 6Li-capture and Pulse Shape Discrimination • Strong rejection of accidental and
correlated neutron backgrounds
6Li(n,t)α252Cf
n
γ
LiLS
PS
D P
aram
eter
n Li
n Li iiiiiiiiiiiiiiiiiiiiiiiiiLLiiiiiiiiiiiiiiiiiLLLLLLLLLLLiiiiiiiiiLLLLLLLLLLLi+ γ γ γ +++++++++++++++++++++++++++++++++++++++ γ
n Li n
νe p e+
Del
ay P
SD
γ-γ
Prompt PSD
γ
Using simulation/deployment data to understand and mitigate electromagnetic-neutron capture correlated backgrounds
Background Rejection & Signal Selection
Miami 2014 Ke Han, Yale University 25
PROSPECT2 operating @ HFIR g
~2 liter Li-LS detector in small B-poly/ lead shield
- not representative of final shield design but useful for MC validation
Studies Underway: • Muon correlations • Detailed simulation
comparison • Internal background
contribution (Rx off) •
Miami 2014 Ke Han, Yale University 27
PROSPECT Physics Potential
Single component HEU core measurement will complement existing LEU spectrum measurements
• Additional model constraint from single, well modeled, reactor
Oscillation:
Multiple segmented detectors probe wide L/E span, improving sensitivity over Δm2 range of interest.
• Phase I can rapidly provide significant physics potential
• Phase II can address majority of suggested phase space
Miami 2014 Ke Han, Yale University 28
• Reactor neutrinos are a tool for discovery. – Reactors are flavor pure sources of anti-νe for FREE
• Current reactor experiments (L~1-2km) provide precision data on θ13, and reactor antineutrino flux and spectra. Precision measurements will be input to long-baseline neutrino experiments.
– Daya Bay, RENO, Double Chooz
• Medium-baseline experiments (L~60km) may offer <1% precision oscillation physics and a window to the mass hierarchy.
– JUNO, RENO-50
• Short-baseline (L~10m) measurements offer opportunities for precision studies of reactor spectrum and a definitive search for short-baseline oscillation and sterile neutrinos.
– PROSPECT,
Summary & Outlook
Miami 2014 Ke Han, Yale University 29