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Down-to-earth searches for cosmological dark matterCarter Hall, University of Maryland
October 19, 2016
Astrophysical evidence for dark matter
Ω Galaxy cluster collisions Rotation curves
3 3
380,000 years after the big bang
Today
1970’s - 1980’s: Cold dark matter is needed to seed the formation of galaxy clusters
13.9 billion years
Credit: Andrey Kravtsov, KICP, U. Chicago
4
Temperature and density fluctuations are 1 part in 105.
The cosmic microwave background anisotropy imaged Planck (2014).
5
CMB multipole expansion - measured by Planck (2014)
Prominent 3rd peak indicates presence of matter which did not rebound.
~ 1°
~ 1/2°~ 1/3°
Neutrinos? – not heavy enough
‘Weakly Interacting Massive Particle’
generalize
Early universe plasma
Age of universe ~ 1 nanosecond;Temperature ~ 100 GeV
?
Dark matter
Dark matter
Normalmatter
Normal matter
Dark matter annihilation
Dark matter creation
The thermal hypothesis:Was the dark matter an interacting component in the very early universe?
Correct dark
matter abundance
Large annihilation cross section
Small annihilation cross section
Typical weak nuclear force cross sections
J. Feng, Annu. Rev. Astron. Astrophys. 2010. 48:495–545
The thermal hypothesis:Was the dark matter an interacting component in the very early universe?
The Milky Way’s dark matter halo
• Typical orbital vel. = 230 km/sec~ 0.1% speed of light
• Density: ~ 300 mproton / liter• WIMPs (~100 GeV): 3 per liter
• deBroglie wavelength:• WIMPs: larger than a nucleus.
Coherent scalar scattering on ordinary nuclear matter, σ ~ A2
• Production: • WIMPs: thermal
?
Dark matter
Dark matter
Normalmatter
Normal matter
Dark matter annihilation
Dark matter creation
HAWC projected five-year sensitivity (start 2015)
?
Dark matter
Dark matter
Normalmatter
Normal matter
‘Direct detection’
WIMP γ,β
‘Direct Detection’
nuclear recoil signal
electron recoil background
The parameter space of direct detection
& XENONNT
Nuclear recoil energy spectra
From: arXiv:1107.1295
A2 dependence
Calibration of LUX: Beta spectrum of Carbon-14
Carbon-14 beta decay
Xenon-131 Gamma line
(164 keV)
Detector threshold = 1.3 keV
1- 8 keV: x-ray region
20 20
Target
scintillating bolometers (CRESST)
Cryogenic semiconductors
(CDMS)
Light
Phonons/heat 100% energy slowest cryogenics
Ionization
WIMP
WIMP
• Nuclear recoils vs. electron recoils ◆ "Division of energy ◆ "Timing ◆ "Stopping power
Two-phase noble liquids (PandaX, XENON, LUX)
Detection modes for ionizing radiation
Single-Phase noble liquids (XMASS, DEAP/CLEAN)
22
Typical Event in LUX
S1S2
23
Strong background rejection from kinematics
~ MeV γ
must cross
full volume without
interacting again
~ keV deposition
forward scattering
24
Simulation of self-shielding in liquid xenon
Volume cut rejects most gamma backgrounds.
25
Particle ID: recoil discrimination in LUX
Light
Charge/Light
Charge/Light
Charge/Light
Electron recoils (background)
Nuclear recoils (signal)
Difference
Electron recoil rejection factor:
200 -500
26
LUX assembly – 2010 - 2011
370 kg of liquid xenon
27
Sanford Underground Research Facility
Davis Cavern 1480 m (4200 mwe)
LUX Water Tank South Dakota USA
28
29
Davis Cavern @ SURF, March 2011
30 30
Davis Campus dedication, May 30, 2012
Ana Davis, widow of Ray Davis
Davis Campus water tank, home of LUX
31
On top of the water shield, Sept. 2012
32
LUX installed underground, Sept. 2012
33
LUX recoil bands and energy scales
more charge recombination
less charge recombination
electron recoil band
nuclear recoil band
34
0 10 20 30 40 501
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
log 10
(S2 b/S
1) x
,y,z
cor
rect
ed
S1 x,y,z corrected (phe)
3 6 9 12 15 18 21 24 27 30 keVnr
1.3
1.8
3.5
4.65.9
7.1
keVee
LUX WIMP search data (2013) 160 events observed 85.3 days × 118.3 kg = 10,090 kg�days
2013 initial results (Run 3): Phys.Rev.Lett. 112 (2014) 091303. 2015 re-analysis of Run 3: Phys.Rev.Lett. 116 (2016) 161301.
Light
Charge Light
_______
October 30, 2013
Calibration: external gamma sources (137Cs)
Calibration source guide tubes
Self-shielding makesexternal gamma sources
mostly ineffectual
37
Tritium: an ideal electron-recoil band calibration source
0 2 4 6 8 10 12 14 16 18 200
0.5
1
1.5
2
Electron Kinetic Energy [keV]
Coun
ts/k
eV/d
ay/1
0000
0 at
oms
Tritium Beta Spectrum (Q=18.6 keV, T1/2=12.3 years)
WIMP search range
C
H
H H
T
38
Injection and removal of tritium from LUX, August 2013
−300 −200 −100 0 100 200 300 400 500
10−4
10−3
10−2
10−1
100
Time (hours)
Rat
e (H
z)
S1 <150 [Phe]. Fiducial Volume
Rateτ 1=6.0 ±0.5Hoursτ 2=6.4 ±0.1 Hours
August 8, 2013
Success
10/21/16
Fiducial count rate for S1 < 150 PE
0 100 200 300 400 500 600
0
50
100
150
200
250
300
radius squared (cm2)
drift
tim
e (µ
s)
−20 −10 0 10 20−25
−20
−15
−10
−5
0
5
10
15
20
25
x (cm)
y (c
m)
Tritium event locations in LUX – August 2013
39
Charge vs Light from tritium in LUX at 170 V/cm
178,000 fiducial tritium events 10/21/16 40
Tritium “combined-energy” spectrum
178,000 fiducial tritium events 41
Light yield of liquid xenon
LUX – tritium (100 & 180 V/cm)
Nuclear-recoil calibration w/mono-energetic neutronsD + D → n + 3He En = 2.45 MeV
Nuclear-recoil calibration of LUX Neutron scattering with a neutron generator
LUX final WIMP search results – Run 3 & 4 combined, 2013 - 2016
LUX Run 3 & 4 (2016): arXiv:1608.07648
LUX -> LZ (2020) Scale up LUX fiducial mass by x40
46
LUX
LZ:TotalXe-10TonAc5veXe–7TonFiducialXe–5.6Ton
LUX
47
Xe TPC
Gd-doped liquid
scintillator outer
detector
50 kV high voltage
existing LUX water shield
The LZ Experiment – coming in 2020
LZ Sensitivity (5.6 Tonnes, 1000 live days)
48
2.5×10-48cm2
History of WIMP sensitivity @ 50 GeV
LUX & PandaX-II (2016) LZ
Ge, NaI no discrimination
Ge, w/discrim.
LXe, w/discrim. ZEPLIN
XENON 1T
XENON100
LUX (2013)
51
Uranium-238 decay chain
Thorium-232 decay chain
end end
start
start
gamma sources
52
Tl-208 (Th-232) Bi-214
(U-238) K-40
Ge-76
Xe-136 Te-130
ββ0ν Q values:
Ordinary radioactive decay here on earth
WIMP scattering
Two problems from particle physics 1) Why is the weak scale so light? è New weak physics? è WIMPs
2) Why no CP violation in QCD ? è Peccei-Quinn symmetry?è Axions
54
Electron-recoil and nuclear-recoil calibration data
Is LUX a success?
July 22, 2016
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