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