THE NEXT STEP IN THE SEARCH FOR
WIMPS WITH NOBLE LIQUID TARGETS
ELENA APRILE
COLUMBIA UNIVERSITYCOSMIC CONTROVERSIESKICP-UNIVERSITY OF CHICAGO,OCTOBER 7,2019

Dark Matter Particle CandidatesExpected nuclear recoil spectrum
SS(u)

10Xe

110SS(u)1341Expected WIMP Rate in a Terrestrial Detector
0.1

0.1

Z vmax0.01

dR⇢0= NNdER
mW
0.001-410 012128

Xe

0.01

ddvf (v)vdER
0.001-434uvmin

56FIG. 12. (color online). Same as Fig. 6 but for 134 Xe.

1234u512100136
11SS(u)Sp(u) 1b currents
Sn(u) 1b currents
Sp(u) 1b + 2b currents
2Sn(u) 1b + 2b currents

10.1

0.001

0.01

S00(u) 1b currents
S11(u) 1b currents
S01(u) 1b currents
S11(u) 1b + 2b currents
S01(u) 1b + 2b currents

F0.01
1S0.01

1910Sij(u) S (u)

127

0.001
0.1

129-4

100.01

SIXe-410 0

1234u

56-5

100.001

0.001-4-610 010FIG. 13. (color online). Same as Fig. 6 but for 136 Xe.

Heavy WIMPs
0.0001010

1234

5butions only from the L = u0 multipole and is modelindependent:

2 2 2J + 1
S(0)
=A(9)
FIG. 11. (Color online)S Structurecfactors
Sp. (u) (solid lines)
04⇡
127
2 2and Sn (u) (dashed) for
I as a function of u = p b /2 withThis reflects
the well-knownof thelevel,
contribub = 2.2801
fm. Results
are shown atcoherence
the 1b current
andof allnucleonsThein SI
scattering.
Consequently,
also tions
including
2bAcurrents.
estimatedtheoreticaluncertaintyis given
thered (Sp (u)) andblue (Sfactors
near
u = 0bythespin-averaged
structureare essenn (u)) bands.

tially identical for all xenon isotopes, apart from small
variations in A2 .
127
2329
Because 4.of angularmomentum
only L = 0
I, 19 F,Na, 27 Al,coupling,Si
multipoles contribute to the structure factors of the evenmass isotopes. As discussed in Sec. II, parity and time
Inreversal
Figs. 11,12, andthe13,multipoles
we show totheeven
structure
facconstrain
L for elastic
127
1923
27
29

SI recoil spectrum-711234uLightWIMPs
1235

64

FIG. 15. (color online). Same as Fig.
14 1bbutcurrents
for 129 Xe.
S (u)
0.1

19p

FSn(u) 1b currents
0.01
Sp(u) 1b + 2b currents
multipole at u ⇠ 1.7 and u ⇠ 4.4 is the L = 2 multipoleSn(u) 1b + 2b currents

relevant,
but the structure factor at these u values is0.001
suppressed with respect to SS (0) by over four and six-4
orders10 of magnitude, respectively.
Finally, we list in Table II the coefficients of the fits
-510
performed
to reproduce the calculated structure factors
for eachisotope.
-6Si(u)ArSiXe1000.1Si(u)Ge

10This work
Helm form factor
Fitzpatrick et al.

1000

I 100 GeV
M=WIMP
0.1
σWn=1×10-47 cm

Xe

6FIG. 14. (color online). Structure factor SS (u) for 128 Xe (thiswork, black dots) in comparison to the Helm form factor (solidred line) [25] and to the structure factor from Fitzpatrick etal. (dashed green line) [15].

Structure factor
Fit

1000

10 0SD

10V.

10-7COMPARISON TO HELM FORM FACTORS
012345AND OTHER CALCULATIONS

u5Key Requirements
muons
neutrinos

neutrons frommuons

neutrons
frommaterials
gamma, beta
radiation frommaterials

Detectors must be massive, with low energy thresholdand effective discrimination of background produced by:(1) Cosmic rays
(2) Intrinsic radioactivity (U,Th,K,Co)(3) ultimately solar, atmospheric and SN neutrinos

WIMP Searches Worldwide

SNOLab
DEAP/CLEAN
PICO
DAMIC
SuperCDMS

SoudanCDMSII
CoGeNT

YangYangKIMS
COSINE

BoulbyDRIFT

Homestake
LUX-LZ

Kamioka
XMASS
NewagePICOLON

ModaneEDELWEISSMIMACCanfranc
ArDM
Rosebud
ANAIS

Gran Sasso
XENON
CRESST
DAMA/LIBRACOSINUSSABRENEWSDarkSide

South PoleDM IceJinping
Panda-X
CDEX

SI WIMP-nucleon cross section [cm2]Where do we stand?
1038

1039

CR

ESS
T-II

DAMA/I

10 40
10 41
10DAMIC

Dar

DAMA/Na

CD
MSkSi

42

CRESST-II

lite

de-50

(nq8SuperCDMS-50edi
Skr
Da
00
1N
O
N
XE

10 44

10C3F
06OPIC)

10 43

10F3I
C
06PICO

DEAP-3600-floor

45

LUX

Current limits

T1NONE
X46oj)
rp(ZL/TnNOXENINDARW

10 47
10 48
10IIX
adnPa

~ 1 event/ kg-day14)
02,dralil-floor (B49

1235102030

50100
2WIMP mass [GeV/c ]2005001000~ 1 event/ tonne-year

Heavy (> 10 GeV) WIMP Searches led by LXe Detectors

Liquid Xenon Targets

LUX
PandaX-II

Irreducible Background:Noble Liquid targets: superior performance also forlight( < 10 GeV) WIMPs Search

Dark Matter-Nucleon σSI [cm2]

10−38
10−39
10−40
10−41
10−42
10−43
10−44
10−45
5×10−1DarkSide-50

DarkSide-50 Binomial
DarkSide-50 No Quenching Fluctuation
NEWS-G 2018
LUX 2017
XENON1T 2017
PICO-60 2017
PICASSO 2017
CDMSLite 2017
CRESST-III 2017
PandaX-II 2016
XENON100 2016
DAMIC 2016
CDEX 2016
CRESST-II 2015
SuperCDMS 2014
CDMSlite 2014
COGENT 2013
CDMS 2013
CRESST 2012
DAMA/LIBRA 2008
Neutrino Floor

123 2 4M χ [GeV/c ]Phys. Rev. Lett. 121 081307 (2018)56 7 8 9 10https://arxiv.org/abs/1907.11485

8

What makes Noble Liquids ideal WIMP Targets?
Boiling Pointat 1 atm [K]Z(A)Density [g/cm3]

Ionization[ e-/keV]

scintillation [photon/keV]

Ar18(40)

87.3

1.40

4240

Xe54(131)

165

3.06

6446

Dense liquids: for massive and homogeneous targets at modest cost (~2k$/kg of LXe)
Easy to purify and keep cold: mature cryogenic and purification technologies
Radiopure liquids: no intrinsic radioactivity (other than Kr85 /Ar39 which can be removed
to required levels). Long-lived isotopes 136Xe (double beta decay) and124Xe (doubleelectron capture) are an added asset for LXe detectors.
Two signals: excellent ionizers and scintillators

Light and Charge Signals in Noble Liquids
escape electron
charge signal (S2)Electronic recoils

ionoitazni

Xe:178 nm
Ar: 128 nm

recombination

excitation

scintillation (S1)Elastic nuclear
Heat

Nuclear recoils

scattering

The power of combining two signals for precise Energy measurement✓◆
S1
S2
E = (nph + ne ) · W =+·W
g1
g2
Example for XENON1T: excellent linearity and resolution from ~ keV (DM) to ~ MeV (0vbb)
world-record 0.8% relative energy resolution (σ/Ε) around 2.5 MeV (136Xe 0νββ energy)

S2
g2=EW

g2 S1
g1 E

Two-phase Noble Liquid Time Projection Chamber:a 3D imaging detector with keV energy threshold

Background, (ER)(S2/S1)ERThe XENON1T
Time Projection Chamber

127 PMTs in the top array

121 PMTs in the bottom array

Light ~4 pe ~28 photons
Charge ~250 pe~10e charge

3.2t (2.0t active) LXe@170K

Time (micro second)Noble Liquid TPCs (20-2000 kg active target)

XENON100 at LNGS
Active Target: 62kg

LUX at SURF
Active Target: ~250 kg

30cm

PandaX-II at CJPL-1
Active Target: ~580 kg

XENON1T at LNGS
Active Target: 2000 kg

48 cm

DarkSide-50 at LNGS
Active Target: 50kg

60 cm

~2008 - 2018from ~10-43 cm2 to ~10-47 cm2
100 cmEvolution of LXeTPCs as WIMP detectors
XENON1T

Fiducial mass [kg]PandaXLUXXENON100XENON105

2008
1000

34

118

306

2012

2016

2017

5.3

2.6

0.8

Lowestbackground everachieved by adirect dark matter
experiment!
1300

2018
0.2

Low-energy ER background[ events / (tonne keV day) ]12ν Double
ElectronCaptureof124

175

20015cObservation 125
ofI attwo-neutrino
double electron capture in
67.3 keVeV to 72 keV

EventV[keV−1]

150105505560

657075

Electron capture80

Xe with XENON1TNeutrino emission

eEnergy [keV]

-03

2017

ν
X

ucial volumeeeeV and σ = (2.6±0.3) keV

Half-life T1/2 = (1.8±0.5stat±0.1sys)×1022 y
ALPS 2019 - 25.04.19

K L M N
Atomicrelaxation

2νECEC

124Xe + 2e- → 124-05

2017

2017-072017-09201

17.5

Q2νECEC = 2857 keV
15.0

1eutrRn generDtRrcDlibrDtiRn

12.5

E2νKK = 64.3 keVν

K L M N

DDte20.0

CRrrected 125I 5Dte [events/t/d]−3Te + 2νe10.0

241AmBe
cDlibrDtiRn

7.5
5.0
2.50.0050

100

150200250

DDy• Electrons filling vacancies → detection of X-rays and Auge

19

• Total energy for double-K shell capture: (64.3±0.6) keV• Background from 125I produced by activation of 124Xe• Currently leading lower limit from XMASS collaboration
Chiara Capelli

16

ALPS 2019 - 25.04.19

most stringent such limit so far reported. Assuming theDine-Fischler-Srednicki-Zhitnitsky model, which postulates the axion as the phase of a new electroweak singlet
scalar field coupling to a new heavy quark, the upper limit
in coupling corresponds to an upper limit on axion mass of
0.12 eV=c2 , while for the Kim-Shifman-VainshteinZhakharov description, which assumes the axion interacting with two Higgs doublets rather than quarks or leptons,
masses above 36.6 eV=c2 are excluded.
In the galactic ALP study, a scan over masses has been
performed, within the range of 1–16keV=c2 , limited by therange over which precise knowledge of light and charge
yield is determined through tritiated methane calibration
data [33]. Assuming that ALPs constitute all of the galactic
dark matter, the 90% C.L. upper limit on the coupling
between ALPs and electrons is shown in Fig. 7 as afunction of the mass, together with the results set by other

XENON1T: constraints on Axions, Axion-Like Particles and Dark Photons

ted on the two dimensional space
1c , for massless solar axions (top)
ALPs (bottom).

▸ Pseudoscalar bosonic DM (ALPs) couples to SM axial current▸ Vector bosonic DM (dark photons) couples weakly to SM photons via kinetic mixingson), a boost factor has been
the likelihood of finding asearches as compared to thely to a search performed only
obal p value is evaluated ascorresponding to a 1.6σ rejec-▸ Absorption cross section is proportional to photoelectric cross section. Signature is peak at particle mass
Solar axions, LUX PRL 118, 2017

upper limit on the coupling gAeelectrons is shown in Fig. 6,
by the previous experiments
ysical limit set via the Red] and the theoretical models

ALPsers in the best fit to the 2013 LUX
nts are Gaussian with means andEvents counts are after analysis
ed in Ref. [25].

straintFit value (solar axions)! 69! 96
! 27
! 12

157 ! 17
175 ! 18
113 ! 18
42 ! 81.29 ⇥ 1019 2 ⇣ ma ⌘ ⇣ pe ⌘R'gaekg 1 d 1
AkeVbFIG. 6. Red curve: LUX 2013 data 90% C.L. limit on thecoupling between solar axions and electrons. Blue curve:90% C.L. sensitivity, !1σ (green band), and !2σ (yellow band).

261301-5

1meV

1eV

1keV

1MeV

1GeV

1TeVdark photons
4 ⇥ 10R'A

230↵↵✓keVmv◆⇣

peb⌘

kg 1 d 1Rates assume ρ0=0.3 GeV/cm3

Next Step:
Generation 2 LXe and LAr DM Experiments

From
XENON1T
toXENONnT

Cryogenics and Purification

DAQ and Slow Control
Calibration
Kr Column(distillation)

TPC

Muon Veto Detector

EPJ-C 77 (2017)www.xenon1t.org

Xenon Storageand Recovery

A more massive and lower background LXeTPC
XENON1T Infrastructureand sub-systems alreadyoperative

1/10 reduction ofbackground and x10
sensitivity improvement

Aprile et al., Eur. Phys. J. C (2017) 77

Fast turnaround:commissioning of LXePUR
ongoing. TPC in this Fall

Some upgrades aimed at
reducing Rn220 already
implemented and working+Figure 3: The ‘grey room’ assembled in front of the Water Tank entrance. (left) The clean room in Hall diMontaggio (right).

Condenser

Distillation stages
Piston pump

ReboilerLiquefier

New TPC

LXe Purification

8.4 ton (5.9 active)

To achieve fast cleaning of the large LXeTime Projection

volume (5000 SLPM)

Chamber

Radon Distillation
To remove the 222Rn
emanated inside thedetector

Figure 4: Drawing of the neutron veto system.

Neutron Veto

the cryostat to enhance neutron tagging efficiency. According to Monte Carlo studies, a fourfold
coincidence among the n-veto PMTs will correspond to a neutron tagging efficiency of almost
90%. The PMTs have been ordered and will arrive in March, where they will be tested for darkrate, gain, single photoelectron response etc., by June.

To tag and measure in situ
4

neutron-induced backgroundA more massive and lower background LXeTPC
XENON1T Infrastructureand sub-systems alreadyoperative

1/10 reduction ofbackground and x10
sensitivity improvement

Aprile et al., Eur. Phys. J. C (2017) 77

Fast turnaround:commissioning of LXePUR
ongoing. TPC in this Fall

Some upgrades aimed at
reducing Rn220 already
implemented and working+Figure 3: The ‘grey room’ assembled in front of the Water Tank entrance. (left) The clean room in Hall diMontaggio (right).

Condenser

Distillation stages
Piston pump

ReboilerLiquefier

New TPC

LXe Purification

8.4 ton (5.9 active)

To achieve fast cleaning of the large LXeTime Projection

volume (5000 SLPM)

Chamber

Radon Distillation
To remove the 222Rn
emanated inside thedetector

Figure 4: Drawing of the neutron veto system.

Neutron Veto

the cryostat to enhance neutron tagging efficiency. According to Monte Carlo studies, a fourfold
coincidence among the n-veto PMTs will correspond to a neutron tagging efficiency of almost
90%. The PMTs have been ordered and will arrive in March, where they will be tested for darkrate, gain, single photoelectron response etc., by June.

To tag and measure in situ
4

neutron-induced background21

at SURF (~2020)

Simulated LZ full exposure with 40 GeV/c2 WIM
1000 days, 5.6 Tons
electronrecoilband

nuclearrecoilband

LZ: 40 GeV WIMP, 1000 days, 5.6 t fiducial

DarkSide-20K at Gran Sasso (~2022)
two-phase TPC with 20-tonnes
fiducial underground Ar with <1 μBq/kg)
Facilities (URANIA and ARIA) toproduce UAr depleted in Ar39 bymulti-path cryogenics distillation
TPC acrylic vessel surrounded byatmospheric Ar + acrylic shell as
neutron veto
Cryogenic SiPMs as photosensors:
8280 in TPC, ~3000 in Veto
DarkSide-LowMass: 1 tonne fiducial
UAr detector for WIMPs<10 GeV

Complementarity of Targets
essential to better constrain WIMP mass and x-section once we have signals!

More in the future: Generation 3 Noble Liquid
Detectors to reach the Neutrino floor
30 tons fiducial LXe (DARWIN)▸ 200 ton×year exposure to reach the neutrino floor

300 tons fiducial LAr(ARGO)▸ 3000 ton×year exposure to reach the neutrino floor

More in the future: Generation 3 Noble Liquid
Detectors to reach the Neutrino floorDark Matter-Nucleon σSI [cm2]10−3710−38ES
SCD T-IMS
IILi
te 20120 91730 tons fiducial LXe (DARWIN)−3910CR−40exposure
toreachtheneutrinofloor▸ 200 ton×year−41Da
1010−4210−43

10−4410rk

ATLAS 2018 (Vector Z', 95% CL)

Side-5170200-36PA
E
D
19020063
DEAP1708211720
UX0L
205II roj.
edXiAS
ND 600 p
AP
Dark
18 EAP-302D1TNONXEoj.
rp
LZoj.
rp
nT proj.
NONXE t× yr
00 oj.
2k20 yr pred
Si 00t×kj.
roar
2DpINyrW×Rt
A
D
00
03ArgoNeutrino floor on xenon

300 tons fiducial LAr(ARGO)
0SuperC

DMS pr2018oj.

DarkSiton×year
exposure
toreachtheneutrinofloor▸ 3000de
LM proj.
10−45

10−46
10−47
−48

1010−49
10−50

−310

10−2

10−1
M χ [TeV/c2]

110102

Conclusions▸ Over next decade experiments using noble liquids will reach unprecedented
sensitivities to search and nail down the WIMP as an explanation for DM

Conclusions▸ Over next decade experiments using noble liquids will reach unprecedented
sensitivities to search and nail down the WIMP as an explanation for DM