Status of the XENON Dark Matter Project
Recent Results from XENON100 and Prospects for Detection
with XENON1T
Guillaume Plante
Columbia University
on behalf of the XENON Collaboration
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
XENON Program
XENON10
XENON100
2005-2007
2008-2015
25 kg
161 kg
Achieved (2007)
Achieved (2011)
−44
2
σSI = 8.8 × 10
cm σSI = 7.0 × 10−45 cm2
Achieved (2012)
σSI = 2.0 × 10−45 cm2
Guillaume Plante - XENON
XENON1T/XENONnT
2012-2017 /
∼2017-2022
3300 kg / 7000 kg
σSI
Projected (2017) / Projected (2022)
∼ 2 × 10−47 cm2 / σSI ∼ 3 × 10−48 cm2
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
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XENON Collaboration
Guillaume Plante - XENON
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
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XENON Collaboration
Guillaume Plante - XENON
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
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Why Xenon?
•
Large mass number A (∼131), expect high rate for SI interactions
(σ ∼ A2 ) if energy threshold for nuclear recoils is low
•
∼50% odd isotopes (129 Xe,
for SD interactions
•
No long-lived radioisotopes (with the
exception of 136 Xe, T1/2 = 2.1 ×
1021 yr), Kr can be reduced to ppt
levels
•
High stopping power (Z = 54,
ρ = 3 g cm−3 ), active volume is self
shielding
Efficient scintillator (∼80% light
yield of NaI), fast response
•
Scalable to large target masses
•
Nuclear recoil discrimination with simultaneous measurement of scintillation and ionization
Guillaume Plante - XENON
Si (A = 28)
Ar (A = 40)
Ge (A = 73)
Xe (A = 131)
10−3
Total Rate [evt/kg/day]
•
131 Xe)
10−4
10−5
σχN = 1 × 10−44 cm2
0
10
20
30
40
50
Eth - Nuclear Recoil Energy [keV]
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
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Dual Phase TPC Principle
Guillaume Plante - XENON
•
Bottom PMT array below cathode, fully immersed in LXe
to efficiently detect scintillation signal (S1).
•
Top PMTs in GXe to detect the proportional signal (S2).
•
Distribution of the S2 signal on top PMTs gives xy coordinates while drift time measurement provides z coordinate
of the event (XENON100: ∆r < 3 mm, ∆z < 300 µm)
•
Ratio of ionization and scintillation (S2/S1) allows discrimination between electron and nuclear recoils.
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
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XENON100: Detector
•
Goal was to build a detector with a ×10 increase in fiducial mass
and a ×100 reduction in background compared to XENON10
•
All detector materials and components were screened in a dedicated low-background counting facility
•
161 kg LXe: 62 kg target surrounded by a 99 kg active veto
•
15 cm radius, 30 cm drift length active volume
•
242 low-activity Hamamatsu R8520-06-Al 1” square PMTs
•
98 tubes on top, 80 on bottom, 64 in the active veto
•
Cathode at -16 kV, drift field of 0.533 kV/cm. Anode at 4.4
kV, proportional scintillation region with field ∼12 kV/cm
•
Installed in a 20 cm H2 O, 20 cm Pb, 20 cm polyethylene, 5 cm
Cu passive shield to suppress external backgrounds
•
Guillaume Plante - XENON
Aprile et al., Astropart. Phys. 35, 573, 2012
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
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XENON100: LNGS
Lab
✑
✑❤ ❤ ❤❤ ❤❤
✑
❤❤ ❤
❤❤
Outside Buildings
Tunnel
Guillaume Plante - XENON
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
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XENON100: Typical Low Energy Event
184
182
180
Amplitude [V]
TPC
179
S1: 14.1 pe
0.3 S2: 926.1 pe
41
63
80
90
75
89
81
92
97
98
93
82
65
193
14
42
64
0.1
0.00
0.2
0.4
0.6
94
87
73
66
83
84
86
68
71
70
69
50
49
48
51
194
15
43
195
16
25
206
205
170 171 172 173 174 175 176 177
24
18
45
204
203
202
218
219
220
197
198
20
22
196
19
21
23
17
44
46
47
26
207
67
85
72
52
27
0.0
-0.6 -0.4 -0.2 0.0
96
88
95
53
208
0.05
74
28
0.20
0.05
79
77
192
13
40
62
76
55
54
29
209
0.2
0.10
30
210
0.10
0.15
31
61
0.15
0.30
0.25
1
57
56
0.40
0.35
12
91
32
2
60
58
78
33
191
38
39
59
34
190
10
11
37
36
189
35
4
3
188
9
6
5
181
8
7
183
187
186
185
199
200
201
0.00
217
Veto
1.5
Amplitude [V]
221
216
222
215
223
99 100 101 102
214
1.0
224
103 104 105 106 107 108 109
213
119 120 121 122 123 124 125 126 127 128
212
0.5
225
110 111 112 113 114 115 116 117 118
226
129 130 131 132 133 134 135 136 137 138
211
227
139 140 141 142 143 144 145 146 147 148
0.0
242
0
20
40
60
80
100
Drift Time [µs]
120
140
160
159 160 161 162 163 164 165 166 167
241
229
168 169 170 171 172 173 174
240
230
175 176 177 178
239
231
238
232
237
Guillaume Plante - XENON
228
149 150 151 152 153 154 155 156 157 158
180
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236
235
234
233
8 / 35
XENON100: ER/NR Discrimination
60 Co,232 Th
AmBe
•
Background in the energy region of interest is due to low energy Compton scatters from high
energy gamma rays or β decays.
•
Electronic recoil band calibration performed with high energy gammas from
Nuclear recoil band calibration performed with AmBe neutron source.
•
Since WIMPs are expected to elastically scatter off of nuclei understanding the behavior of single
elastic nuclear recoils in Xe is essential.
Guillaume Plante - XENON
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
60 Co
and
232 Th.
9 / 35
XENON100: Nuclear Recoil Energy Scale
Nuclear recoil equivalent energy Enr is
obtained from the S1 signal
Enr =
1
Ser
S1
Ly,er Leff (Enr ) Snr
0.30
Ly,er = 2.28 ± 0.04 pe/keVee, light
yield of ER from 122 keV γ rays
•
0.35
•
Ser = 0.58, Snr = 0.95, scintillation
light quenching due to drift field
•
Relative scintillation efficiency Leff
0.25
Leff
•
0.15
0.10
0.05
Ly,nr (Enr )
Leff (Enr ) =
Ly,er (Eee = 122 keV)
ϕ=
2
3
H(d, n) He
d
0.20
Arneodo 2000
Bernabei 2001
Akimov 2002
Aprile 2005
Chepel 2006
Aprile 2009
Manzur 2010
Plante 2011
0.00
1
2
3
4 5 6 7 8 910
20
30 40
100
Energy [keVnr]
π
2
EJ301
n
LXe
•
Record fixed-angle elastic scatters of monoenergetic
neutrons tagged by organic liquid scintillators with
n/γ discrimination
•
Measurement performed at Columbia University, lowest energy measured 3 keV
θ
θ
EJ301
Er ≈ 2En
mn MXe
(1 − cos θ)
mn +MXe 2
Guillaume Plante - XENON
•
Plante et al., Phys. Rev. C 84, 045805 (2011)
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
10 / 35
XENON100: Latest WIMP Search Data Released: 225 Days
S1 [PE]
Radius [cm]
2
4
6
8
10
12
14
5
15.3
10
15
20
25
30
0
0.4
-5
z [cm]
-10
-15
0.0
-0.2
-0.4
b
-20
log (S2 /S1)-ER mean
0.2
10
-25
-30
0
50
100
150
200
250
-0.6
-0.8
Radius2 [cm2]
-1.0
-1.2
5
10
15
20
25
30
35
40
45
50
Energy [keVnr]
•
2 candidate events observed within 34 kg fiducial volume
•
Probability that the background fluctuates to 2 events when expecting 1.0 ± 0.2 is 26.4%
•
Profile Likelihood analysis cannot reject background-only hypothesis
•
No evidence for a dark matter signal
Guillaume Plante - XENON
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
11 / 35
XENON100: Spin-Independent Results
•
Exclusion limits derived with profile likelihood method, σSI < 2.0 × 10−45 cm2 @ 50 GeV/c2
•
Up until the latest LUX results (10/2013), was the strongest limit over a large WIMP mass range
•
Aprile et al., Phys. Rev. Lett. 109, 181301 (2012)
Guillaume Plante - XENON
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
12 / 35
Calculate the NR response
•
•
•
Start with
sion spectrum
neutron emis-
104
Data
Bezrukov Qy
Best Fit Qy
103
•
Source strength measured (PTB) as
160 ± 4 n/s
•
Propagate neutrons through a detailed Geant4 detector geometry
•
Convert energy deposits into observable S1 and S2 signals using Leff
and Qy , including thresholds, resolutions, and acceptances from data
First step: use the measured Leff from
scattering experiments and derive the
optimum Qy by reproducing the measured S2 spectrum
Excellent agreement between MC and
measured S2 spectrum
E. Aprile et al., Phys. Rev. D 88, 012006 (2013)
102
0
-
•
241 AmBe
Qy [e /keVnr]
•
Counts
XENON100: Response to Nuclear Recoils
2000
3000
4000
5000
6000
7000
8000
cS2 [PE]
11
Aprile 2006, 0.2 kV/cm
10
Sorensen 2009
Manzur 2010
Horn 2011
Bezrukov Qy
9
8
7
XENON100 (this work)
6
5
4
3
2
2
Guillaume Plante - XENON
1000
10
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
102
Energy [keV nr ]
13 / 35
XENON100: Response to Nuclear Recoils
3.0 ×10
Second step: use the optimum Qy obtained to calculate the MC S1 spectrum
and derive a new Leff
•
Counts
3
2.0
Excellent agreement between measured
S1 spectrum and MC down to 2 pe
•
1.5
Indirect Leff obtained consistent with direct measurements
•
Data
Aprile L
eff
Best Fit Leff
2.5
1.0
0.5
Confirms robustness of the XENON100
Leff parametrization down to 3 keVr
1
Leff
2.6
Data
2.4
10
102
cS1 [PE]
0.30
Aprile 2009
MC
10
log (cS2/cS1)
•
0.25
2.2
0.20
2.0
Manzur 2010
Plante 2011
Horn 2011
Aprile 2011
XENON100 (this work)
0.15
(MC-Data)/Data
1.8
1.6
0.040
0.02
0.00
-0.02
-0.04
0
0.10
20
40
60
80
100
120
140
0.05
20
40
Guillaume Plante - XENON
60
80
100
120
140
cS1 [PE]
2
10
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
102
Energy [keV nr ]
14 / 35
XENON100: Axion Searches
Axions and axion-like particles can couple
to electrons via the axio-electric effect
•
2
2
σAe = σpe (E)
3E
gAe
β 16παme 2
1−
β
2/3
3
!
•
Analogous to the photoelectric effect with
an absorbed axion instead of a photon
•
Expect electronic recoils from axio-electric
interactions
Solar axions
2.5
5
Expected Mean Recoil Energy [keV]
7.5
10
1
Events/PE
Events/PE
1
Galactic axion-like particles
102
5
10
15
Expected Mean Recoil Energy [keV]
20
25
30
35
1 keV/c2
102
2
5 keV/c
2
8 keV/c
10
2
10 keV/c
10
2
15 keV/c
2
20 keV/c
30 keV/c2
1
0
5
10
15
20
25
30
S1 [PE]
Expected signal for mA < 1 keV/c2
and gAe = 2 × 10−11
Guillaume Plante - XENON
1
0
10
20
30
40
50
60
70
80
90
100
S1 [PE]
Expected signal assuming ALP constitute
all of galactic DM and gAe = 4 × 10−12
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
15 / 35
XENON100: Electronic Recoil Energy Scale
•
Need to know the response of LXe to low energy ER
•
Two recent measurements of the scintillation yield of
ER using the “Compton coincidence technique”
1
Obodovskii (1994)
Aprile (2012)
NEST (v0.98, 2013)
0.8
Eγ
1+
Eγ
me
Re
Er = Eγ −
(1 − cos θ)
0.6
0.4
Aprile et al., Phys. Rev. D 86, 112004 (2012)
Cs
0.2
LXe
detector
γ′
θ
HPGe
detector
•
dN/dE [events keV-1]
PMTs
650
0
630
0.080
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0
0
5
10
15
20
25
30
35
10
20
50
100
200
Compton scatters (this work)
Calibration sources (this work)
Manalaysay (2010)
Aprile (2006)
NEST (v0.98, 2013)
5
10
15
20
25
30
35
1.2
1
40
Recoil Energy [keV]
∼0.75
5
40
θHPGe = 8.6
Eer = 8.2 ± 1.0 keV
EHPGe = [653,654] keV
0.8
0.6
0.4
at low energies
XENON100 energy threshold 2.04 ± 0.21 keV
Guillaume Plante - XENON
2
o
0
•
1
Energy [keV]
At zero field, scintillation yield decreases below 60 keV
Field quenching
0.5
640
0.2
•
Compton scatters (this work)
Calibration sources (this work)
Band used for threshold calculation
660
q(450)
γ
EHPGe [keV]
137
Baudis et al., Phys. Rev. D 87, 115015 (2013)
0.5
1
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
2
5
10
20
50
100
200
Energy [keV]
16 / 35
XENON100: First Axion Search Results
•
Uses the same 225 days data as for spin-independent WIMP search
•
Profile Likelihood analysis cannot reject background-only hypothesis
•
Ultra-low background and low energy threshold enable XENON100 to set competitive limits
•
Analysis made possible by recent measurements of scintillation yield and field quenching of ERs
Solar axions
Galactic axion-like particles
-9
-9
10
10
KSVZ
Si(Li)
DFSZ
-10
10-11
CoGeNT
Ae
EDELWEISS
g
g
10
XMASS
Solar ν
Ae
10
Solar ν
-10
10-11
CDMS
EDELWEISS
XENON100
KSVZ
-12
10-12
10
Red giant
10-13
10-5
-4
10
-3
XENON100
-2
10
10
mA [keV/c2]
-1
10
10-13
1
1
2
3
4 5 6 7 8 910
mA [keV/c2]
20
30
E. Aprile et al., Phys. Rev. D 90, 062009 (2014)
Guillaume Plante - XENON
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
17 / 35
XENON100: Status
•
•
•
Upcoming analysis results
•
Electronic recoil rate stability analysis
•
Light dark matter (“few electrons” S2-only analysis)
•
WIMP-nucleus inelastic interactions
•
154 days of new DM data in 2013 (blinded) under analysis
Improvements in detector characterization
•
Calibrations with AmBe at different drift fields
•
Measurement of low-energy (<5 keVr) NRs from YBe
Continuing data acquisition
•
Online Rn removal tests
•
Novel calibration methods
Guillaume Plante - XENON
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
18 / 35
XENON1T: (Very Near) Future
Guillaume Plante - XENON
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
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XENON1T: (Very Near) Future
Guillaume Plante - XENON
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
19 / 35
From XENON100 to XENON1T: A Few of the Challenges
LXe Mass (kg)
ER Bkgnd (evts/keV/kg/d)
Kr Concentration (ppt)
Rn Concentration ( µBq/kg)
Charge drift (cm)
Cathode HV (kV)
LXe Purification
Cryogenics
Storage/Recovery
Guillaume Plante - XENON
XENON100
161 kg
5 × 10−3
(19 ± 4)
∼65
30
−16
Several Months
∼1 year run
GXe
XENON1T
3300 kg
∼5 × 10−5
< 0.5
∼1
100
−100
Few Months
∼2+ year run
LXe
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
20 / 35
XENON1T: Construction Milestones
Guillaume Plante - XENON
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
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XENON1T: Construction Milestones
Guillaume Plante - XENON
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
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XENON1T: Construction Milestones
Guillaume Plante - XENON
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
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XENON1T: Construction Milestones
Guillaume Plante - XENON
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
24 / 35
XENON1T: Water Cherenkov Muon Veto
Guillaume Plante - XENON
•
Water tank 10 m high and 9.6 m diameter
•
Interior lined with 3M specular reflector foil
•
Water tank construction completed 2013/12
•
84 high QE 8” Hamamatsu R5912 PMTs
•
µ-induced neutron background < 0.01 evt/yr
•
Trigger efficiency > 99.5% for neutrons with
µ in water tank, ∼78% with µ outside
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
25 / 35
XENON1T: Cryostat, TPC
Guillaume Plante - XENON
•
Double-wall vacuum insulated cryostat, constructed from selected low-activity stainless
steel
•
Outer vessel 2.4 m high, 1.6 m diameter, inner
vessel ∼2 m high, 1.1 m diameter
•
3.3 tons LXe, ∼1 m3 TPC, fiducial mass between 1 and 1.5 tons
•
248 3” PMTs Hamamatsu R11410-21, 36%
average QE, < 1 mBq/PMT in U/Th
•
Background ×100 lower than XENON100
•
Custom low-activity high voltage feedthrough
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
26 / 35
XENON1T: Cryostat, TPC
Guillaume Plante - XENON
•
Double-wall vacuum insulated cryostat, constructed from selected low-activity stainless
steel
•
Outer vessel 2.4 m high, 1.6 m diameter, inner
vessel ∼2 m high, 1.1 m diameter
•
3.3 tons LXe, ∼1 m3 TPC, fiducial mass between 1 and 1.5 tons
•
248 3” PMTs Hamamatsu R11410-21, 36%
average QE, < 1 mBq/PMT in U/Th
•
Background ×100 lower than XENON100
•
Custom low-activity high voltage feedthrough
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
26 / 35
XENON1T: Cryogenics
Guillaume Plante - XENON
•
Design based on experience acquired by
operating XENON10, XENON100, and
XENON1T Demonstrator
•
Heat load below 50 W (without circulation)
•
Redundant 200 W pulse tube refrigerators
•
One PTR can be serviced while the other is
in operation
•
Backup liquid nitrogen cooling
•
Circulation at
changers
∼100
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
slpm through heat ex-
27 / 35
XENON1T: Xe Storage
Guillaume Plante - XENON
•
Double-wall, high-pressure (70 atm), vacuum
insulated, LN2 cooled sphere
•
Designed to store ∼7.6 tons of xenon, in liquid
form at −100◦ C or in gaseous form at room
temperature
•
Detector can be filled with liquid xenon directly instead of condensing xenon gas
•
In case of emergency, liquid xenon from the
detector can be recovered in a few hours
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
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XENON1T: Purification
Guillaume Plante - XENON
•
Continuous GXe circulation at
•
Purification using high-flow heated getters
•
Two parallel circulation pumps and purification circuits
•
GXe purity in-situ analytics
•
Continuous monitoring of impurity concentrations (e.g. H2 O)
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
∼100
slpm
29 / 35
XENON1T: Kr Removal
Guillaume Plante - XENON
•
Building custom designed cryogenic distillation column for Kr removal
•
XENON1T Kr/Xe concentration requirement
is < 0.5 ppt, aim at < 0.1 ppt with the column
•
High throughput, 3 kg/hr at 104 separation
•
3.5 tons in
•
Custom gas purity diagnostics (online, 83m Kr
tracer, and offline, ATTA, RGMS, RGA +
cold trap)
∼1.8
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
months (single pass)
30 / 35
XENON1T: Expected Backgrounds
ER background from PMTs, Cryostat
ER background after discrimination
Pr
•
•
Full MC simulation of the detector (TPC,
PMTs, cryostat, water shield) with GEANT4
to predict ER background
•
Neutrons from
SOURCES-4A
•
Total ER background rate expected to be
below 5 × 10−5 evts/keVee /kg/day before
S2/S1 discrimination
Guillaume Plante - XENON
(α, n)
calculated
with
y
r
a
n
i
e lim
Single scatters, 1 ton fiducial volume,
[2, 12] keVee, [5, 50] keVr, 99.75% S2/S1
discrimination, 40% NR acceptance
Source
ER from materials
85
Kr (0.2 ppt nat Kr)
222
Rn (1 µBq/kg)
Solar neutrinos
2ν2β
NR from materials
Total
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
Background (evts/yr)
0.05
0.07
0.08
0.08
0.02
0.24
0.54
31 / 35
XENON1T: Sensitivity
•
Spin-independent WIMP-nucleon interaction cross section sensitivity of 2 × 10−47 cm2
for WIMPs with a mass of 50 GeV/c2
Guillaume Plante - XENON
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
32 / 35
XENONnT: Upgraded XENON1T Detector
Guillaume Plante - XENON
•
Rapid deployment possibility: no modifications
to infrastructure required, only construction of a
larger inner vessel and TPC
•
Additional ∼200 PMTs and DAQ electronics
channels for the upgraded TPC
•
Target mass of ∼6 tons, sensitivity to spinindependent WIMP-nucleon elastic scattering
cross sections of 3 × 10−48 cm2
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
33 / 35
Conclusion
•
XENON100 recent results on axion searches, stay tuned for more results
•
XENON100 is still taking data, continuing to improve detector characterization
•
XENON1T is under construction at LNGS, water tank completed, service building completed
•
Integration and commissionning of primary systems (cryostat, cryogenics, storage, purification)
underway, detector installation by mid-2015
•
Detector commissionning in 2015, first science run starts in 2015
•
XENONnT, possibility of a rapid upgrade path included in the XENON1T design
Guillaume Plante - XENON
DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014
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