Ultra-low Energy Calibration
of LUX Detector using D-D
127
Neutron, Tritium and Xe
Dongqing Huang
Brown University
!
On Behalf of LUX Collaboration
!
UCLA Dark Matter 2016 Conference, Los Angeles
Feb 19th, 2016
The LUX Dark Matter Detector
Dongqing Huang - Brown University, LUX
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UCLA Dark Matter Conference 2016
LUX has Extremely Low Background
•
•
•
1492 m underground
Dongqing Huang - Brown University, LUX
4850 ft (1492 m) underground in the black hills of
South Dakota (4300 m water equiv.)
• reduces muon flux to < 1 muon per day
surrounded by a 7.6 m diameter water shield
• reduces gamma and neutron backgrounds to
< 1 projected event in 300 days of searching
limiting factor is detector construction materials
• this limit is < 2 background events per DAY in
the central 118 kg target in the energy window
of interest
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UCLA Dark Matter Conference 2016
LUX Nuclear Recoil Calibration
using D-D Neutron
D. S. Akerib et al., (LUX Collaboration ), Low Energy (0.7 - 74 keV ) Nuclear Recoil Calibration of the LUX Dark Matter
Experiment Using D-D Neutron Scattering Kinematics, to be published
Corresponding author: James Verbus
nr
Dongqing Huang - Brown University, LUX
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UCLA Dark Matter Conference 2016
Adelphi DD108 Neutron Generator
Fig. LUX Detector hanging inside water tank
Dongqing Huang - Brown University, LUX
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Fig. D-D neutron generator sitting
outside of water tank
UCLA Dark Matter Conference 2016
Neutron Bean in Active Region
0
0
1.5
1
50
50
150
0
200
-0.5
250
100
0.5
150
0
200
-0.5
log10(cts / 6.4 µs / 1.0 cm)
0.5
Drift time [µs]
Drift time [µs]
100
log10(cts / 6.4 µs / 1.0 cm)
1
250
-1
-1
300
300
0
10
20
30
40
50
-20
′
y distance into LXe [cm]
•
•
•
-10
0
10
20
′
x perpendicular to neutron beam [cm]
Neutron generator/beam pipe assembly aligned 16 cm below liquid surface in LUX active
region to maximize usable single / double scatter events
Beam leveled to ~1 degree
107 live hours of neutron tube data used for analysis
Dongqing Huang - Brown University, LUX
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UCLA Dark Matter Conference 2016
Ionization Yield [electrons / keVnra ]
Charge Yield Absolutely Measured Down to 0.7 keV in LUX
Systematic uncertainty due to position
reconstruction energy bias correction
Aprile 2013 (XENON100) - 0.53 kV/cm
Sorensen 2010 (XENON10) - 0.73 kV/cm
Horn 2011 (ZEPLIN-III combined FSR & SSR) - average of 3.6 kV/cm
Aprile 2006 - 0.3 kV/cm
Aprile 2006 - 0.1 kV/cm
Manzur 2010 - 1 kV/cm
Manzur 2010 - 4 kV/cm
LUX model: Lindhard (k = 0.174) + biex. quenching
Alt. LUX model: Ziegler stopping power + biex. quenching
LUX D-D Qy at 180 V/cm
101
Sys. uncertainty due to neutron source spectrum
Sys. uncertainty due to S2 signal corrections and g2
100
100
101
102
Energy [keVnra ]
Dongqing Huang - Brown University, LUX
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UCLA Dark Matter Conference 2016
Ly Measured in LUX Using Absolute Energy Scale down to 1.08 keV
Horn 2011 (ZEPLIN-III combined FSR & SSR)
Aprile 2013 (XENON100)
Manzur 2010
Plante 2011
Aprile 2009
LUX model: Lindhard (k = 0.174) + biex. quenching
Alt. LUX model: Ziegler stopping power + biex. quenching
LUX D-D L at 180 V/cm
y
Sys. uncertainty due to S1 signal corrections and g1
Sys. uncertainty in
83m
Kr yield (right axis)
Kr (32.1 keV)
10-1
83m
101
Ly relative to
Ly [photons / keVnra ]
Sys. uncertainty due to Qy energy scale
Sys. uncertainty due to neutron source spectrum
100
100
101
102
Energy [keVnra ]
Dongqing Huang - Brown University, LUX
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UCLA Dark Matter Conference 2016
LUX Electron Recoil Calibration
using Tritium
D. S. Akerib et al., (LUX Collaboration ), Tritium calibration of the LUX dark matter experiment, arXiv:1512.03133
Dongqing Huang - Brown University, LUX
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UCLA Dark Matter Conference 2016
Tritiated-Methane, The Ideal ER Calibration Source
Methane diffuses much slower than bare tritium
Dissolved uniformly in liquid Xe
High statistics, low energy ER calibration with
unprecedented accuracy
Q = 18.6 keV; Mean = 5 keV; Peak = 2.5keV
Tritiated methane removed from detector via
standard purification technology with time
constance ~6 hours
0
50
drift time (µs)
•
•
•
•
•
100
150
200
250
10
0
300
τ2=6.4±0.1
0
rate (Hz)
10 -1
100
200
300
400
radius squared (cm 2)
500
600
τ1=6.0±0.5
10 -2
10 -3
10 -4
-200
0
200
Time (hours)
Dongqing Huang - Brown University, LUX
400
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UCLA Dark Matter Conference 2016
Energy Reconstruction
E = nr + ne = W (S1 / g1 + S2 / g2)
For electronic recoils in LXe, W = 13.7eV
Measure S1 and S2 then convert to photons and electrons with
gain g1 and g2
5000
Data
Tritium Beta
4000
3000
2000
1000
Frac Res. (σ)
Count/(0.25 keV)
•
•
•
0
0
4
2
0
-2
-4
0
5
10
15
20
5
10
15
20
Energy (keV)
Dongqing Huang - Brown University, LUX
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UCLA Dark Matter Conference 2016
60
60
55
55
50
50
Light Yield (Photons/keV)
Charge Yield (Electrons/keV)
ER Yields Measured with Tritium
45
40
35
30
25
20
15
10
45
40
35
30
25
20
15
1
2
5
Energy (keV)
10
•
•
•
•
1
2
5
Energy (keV)
!
shaded black band: tritium at 180 V/cm
solid red line: NEST v0.98 for 180 V/cm
shaded blue band: tritium at 105 V/cm
dashed green line: NEST v0.98 for 105 V/cm
Matthew Szydagis, Adalyn Fyhrie, Daniel Thorngren, and Mani Tripathi.
Enhancement of NEST Capabilities for Simulating Low-Energy Recoils in
Liquid Xenon. JINST, 8:C10003, 2013. doi: 10.1088/1748-0221/8/10/
C10003.
Dongqing Huang - Brown University, LUX
10
20
10
20
Brian Lenardo, Kareem Kazkaz, Aaron Manalaysay, Matthew
Szydagis, Mani Tripathi. A Global Analysis of Light and Charge
Yields in Liquid Xenon. arXiv: 1412.4417 [astro-ph.IM]
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UCLA Dark Matter Conference 2016
LUX Electron Recoil Calibration
127
using Xe
D. S. Akerib et al., (LUX Collaboration ), Ultra-Low Energy Calibration of LUX Detector using 127Xe Electron Capture, to
be published
Dongqing Huang - Brown University, LUX
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UCLA Dark Matter Conference 2016
Xenon-127 Decay Toy Model
Electron Capture: p + e-→ n + νe
The binding energy and expected EC
probability from that shell
- K: 33.2 keV 83.4%
- L: 5.2 keV 13.1%
cascade X-ray
or Auger
- M: 1.1 keV 2.9%
- N: 190 eV 0.6%
γ-ray"
35.8% 203 keV"
8.1% 375 keV
•
•
•
Cosmogenic activation
νe
Half life: 36 days
Based on the measurement of Apr222013 data, there are ~0.8million 127Xe atoms in LUX
Xenon volume
Dongqing Huang - Brown University, LUX
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UCLA Dark Matter Conference 2016
Xenon-127 EC Decay Event in LUX Detector
Fig. - A real 127Xe decay event with K shell electron capture.
The event waveform appears as one S1 followed by two
well-separated S2
Dongqing Huang - Brown University, LUX
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Fig. - Event Schematics in
Detector
UCLA Dark Matter Conference 2016
Xenon-127 EC Events in Data
Fig. - X-rays’ ER charge spectrum
Fig. - Scatter plot of 127Xe events with area of first
vertex S2 versus are of second vertex S2; “First Vertex”
is the first S2 ordered by drift time
Dongqing Huang - Brown University, LUX
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UCLA Dark Matter Conference 2016
Xenon-127 Qy along with Tritium and NEST v98
Preliminary
Dongqing Huang - Brown University, LUX
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UCLA Dark Matter Conference 2016
Conclusion
has achieved a better understanding of Xe NR and
• LUX
ER response than any other dark matter search
•
•
•
experiment
In-situ calibration
NEST will be refined to fit D-D NR light and charge yields
and Tritium / 127Xe ER yields
LUX new dark matter results comes with these
calibration, with a significant improved sensitivity to low
mass WIMPs
Dongqing Huang - Brown University, LUX
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