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STATUS OF DIRECT WIMP SEARCH EXPERIMENTS
KIAS, Seoul, Korea
Yeongduk KimCenter for Underground Physics, IBS
Sejong University
2013. 11. 14.
2Outline
1. Dark Matter, Direct detection2. Underground Laboratories in the world.3. Direct search experiments – recent4. Experiments at Center for Underground Physics.5. Summary.
1. Dark Matter, Direct detection2. Underground Laboratories in the world.3. Direct search experiments – recent4. Experiments at Center for Underground Physics.5. Summary.
3Particle candidates
Masses and interaction strengths span many orders of magnitude.
HEPAP/AAAC DMSAG Subpanel (2007)
4WIMP DETECTION
c c
q q
Annihilation
(Indirect detection)P
rodu
ctio
n(A
ccel
erat
or)
WIMP
Correct relic density à Efficient annihilation in early Universe
q q
Annihilation
(Indirect detection)
WIMP scattering(Direct detection)
Pro
duct
ion
(Acc
eler
ator
)
cc ® qq(hadrons), e+e- ,m+m- ,t +t - ,nn ®W +W - ,ZZ ®gg ® Zg
Nucleus Nucleusc c+ ® +
5Detection Principle of Direct Search
0/ 20
0
( )0 00
2 22
2 2 ,
2
( )
2
4 1, 3
RE E r
SI SDDWA
SI SDA AWA WA
p
W
SI SIWp n p p
R
pW
R e F qE rNR
dRd
S
A
JAJ
M
Eu r spm ms s s
ms
m
-=
=
+= =
Spin Independent(SD), Spin-Indepent(SI)
Detector
WIMP
Nucleus
0 , ,W DMu r
WIMP-Nucleus elastic scatteringA,Mass,ER
5
0/ 20
0
( )0 00
2 22
2 2 ,
2
( )
2
4 1, 3
RE E r
SI SDDWA
SI SDA AWA WA
p
W
SI SIWp n p p
R
pW
R e F qE rNR
dRd
S
A
JAJ
M
Eu r spm ms s s
ms
m
-=
=
+= =
ExperimentMeasure this
SUSY models
• ER < 100 keV
)χ~χ~( 01
01 NN ®s 10-6 ~ 10-10 pb
Expected event rate< 1/kg/day
Nuclear Physics
6
Recoil Energy Spectra
Recoil Energy (keV)0 10 20 30 40 50 60 70 80 90 100
Event R
ate
/(k
eV
kg d
ay)
-510
-410
-310
-210
-110
1
10
2 cm-42 = 10WIMP-nucleons
WIMP hits CsI
10GeV20GeV
50GeV
100GeV1000GeV
Recoil energy spectra
Measured Energy (keV)0 2 4 6 8 10 12 14
Event R
ate
/(k
eV
kg d
ay)
-510
-410
-310
-210
-110
1
102 cm-42=10WIMP-nucleons
10GeV
20GeV
50GeV
100GeV
1000GeV
Measured energy spectra
Quenching Effect, energy resolution are critical to compare experiments. Quenching Effect, energy resolution are critical to compare experiments.
a few tens of keV
Recoil Energy (keV)0 10 20 30 40 50 60 70 80 90 100
Event R
ate
/(k
eV
kg d
ay)
-510
-410
-310
-210
-110
1
10
2 cm-42 = 10WIMP-nucleons
WIMP hits CsI
10GeV20GeV
50GeV
100GeV1000GeV
a few keV
Measured Energy (keV)0 2 4 6 8 10 12 14
Event R
ate
/(k
eV
kg d
ay)
-510
-410
-310
-210
-110
1
102 cm-42=10WIMP-nucleons
10GeV
20GeV
50GeV
100GeV
1000GeV
7Direct WIMP detection techniques
W
CRESST DAMAKIMS
XMASSANAIS
CUORE
It is a huge advantage if the detector can measure two different signals and see the correlation between the signals to remove unwanted backgrounds.
WW
N+ _+ _
_+
HPGeCoGeNT
Ionization
XENONZEPLIN
LUXDarkSide
DAMAKIMS
XMASSANAIS
CDMSEDELWEISS
9World-wide direct search experiments
SNOLabDEAPCLEAN
PICASSOCOUPPDAMIC
HomestakeLUX
SoudanSuperCDMS
CoGeNT
ModaneEDELWEISS
CanfrancArDM
RosebudANAIS
BoulbyZEPLINDRIFT
Gran SassoXENONCRESST
DAMA/LIBRADarkSide
YangyangKIMS
KamiokaXMASSNewage
JinpingPandaXCDEX
CanfrancArDM
RosebudANAIS
Gran SassoXENONCRESST
DAMA/LIBRADarkSide
KamiokaXMASSNewage
JinpingPandaXCDEX
South PoleDM-ICE
Dark Matter ExperimentsDark Matter Experiments
LUX detector installation at Sanford Underground Laboratory.
12250 kg NaI(Tl) crystals.As a result of a second generation R&D for more radiopure NaI(Tl) by exploiting new chemical/physical radiopurification techniques.(all operations involving crystals and PMTs - including photos - in HP Nitrogen atmosphere)
etching staff at workin clean room
PMT+HV divider
DAMA/LIBRA experiment
Earch velocity (30km/s)
Cu etching with super- and ultra-pure HCl solutions, dried and sealed in HP N2
Earch velocity (30km/s)
16Can muons be the cause of DAMA modulation ?
Muons can’t make the backgrounds nor the modulation directly.
Only ~ 6 muons hits DAMA detector per day. (DAMA group ~ 2 muons)
Backgrounds : 1000 hits at 2-6 keV per day.modulation size is 10 hits per day.
Muons can’t make the backgrounds nor the modulation directly.
250kg NaI crystals
However, each muon deposits ~ 350 MeV in the crystals. It may generate delayed signals even only 0.1% of the deposit energy.
So far, muon induced neutrons etc can’t explain the DAMA modulation quantitatively. [Ralston arXiv:1006.5255]
17CDMS (Cryogenic Dark Matter Search)
§ 19 Ge and 11 Si detectors in 5 “towers” (2006-2009)§ Ge for high-mass, Si run for low mass § 55.9 kg days in 6 Si detectors (2006-2007)§ 140.2 kg days in 8 Si detectors (2007-2009)
ZIPs: Z-sensitive Ionization and Phonon Detectors
7.6 cm diameter 1.0 cm thick
Six detectorsstacked in each tower
Five towers arranged in cold volume4.75 kg of 4.75 kg of GeGe, 1.1 kg of Si1.1 kg of Si
Phonons read out via TES.à energy measurement
CDMS-II Si: 3 Events in nuclear recoil band observed. : 7.8 events/(kg year)
Surface events w/ 133Ba source
Background events expected.
arXiv:1304.4279
Similar Experiments:EDELWEISS : GE+NTD Sensor
Nuclear recoils w/ 252Cf source
21Background rejection in XENON100 exp.
Dots : Background dataRed-graded : Neutron recoil events.
8GeV WIMP signal
Dot : data, Blue : Simulation
8GeV WIMP signal
25GeV WIMP signal 226 days X 34 kg Run à only 2 events.Record-low background level.
Aprile PRD 88, 012006
à 0.1 events/(kg year)
22
COGENT
CoGeNT: a dedicated search for low-mass WI MPs• An excellent example of synergy wit h indust r y: Canber ra s
PPCs around since ear ly 80’s.
• Remarkably simple commercial technology leads to applicat ions in double-beta decay (MAJORANA, GERDA) and ast ropart icle physics (CoGeNT).
• Searches for an annual modulat ion require exquisite inst rumental stabilit y. But how much is enough?
• PNNL/UC/Canber ra C-4 expansion (x10 mass, lower bckgs and t hreshold) will make it, or break it.
HDPEbelow
HDPE above
C-4 design
CoGeNTDAMA/LI BRA
+
CRESST M2 cent roid
PRL 107 (2011) 141301
PRD 84 (2011) 055014(one of many inter pretat ions)
CoGeNT: a dedicated search for low-mass WI MPs• An excellent example of synergy wit h indust r y: Canber ra s
PPCs around since ear ly 80’s.
• Remarkably simple commercial technology leads to applicat ions in double-beta decay (MAJORANA, GERDA) and ast ropart icle physics (CoGeNT).
• Searches for an annual modulat ion require exquisite inst rumental stabilit y. But how much is enough?
• PNNL/UC/Canber ra C-4 expansion (x10 mass, lower bckgs and t hreshold) will make it, or break it.
HDPEbelow
HDPE above
C-4 design
CoGeNTDAMA/LI BRA
+
CRESST M2 cent roid
PRL 107 (2011) 141301
PRD 84 (2011) 055014(one of many inter pretat ions)
23
Annual Modulation Signals are (de)claimed.
In addition to DAMA, CoGeNT experiment shows annual modulation too.
COGENT3.5 years data
But, CDMS didn’t see annual modulation.
CDMSCoGeNTCollar TAUP2013
Similar Experiments w/ PPC :TEXONO, CDEX, MALBECK
24
2 Jun.
Back
grou
nd L
evel
KIMS-CsI annual modulation data
Time
Back
grou
nd L
evel
• 12 crystals (104.4kg).
• 2.5 year data (Sep. 2009–Feb. 2012)
• Background Level : 2~3 cpd/kg/keV l The mean amplitude from 3 keV to 6 keV is 0.0008±0.0068 cpd/kg/keV
26MALBEK
MAjorana Low-Background BEGe Detector at KIRF
New CoGeNT like experimentdidn’t confirm CoGeNT signal.
Giovanetti TAUP2013
27Low mass WIMPs are observed ?
New data from LUX, DarkSide, KIMS-NaI are expected soon !
Not consistent ! à Do we have multiple components in DM ?
Hope to see the solution soon.
27
DAMA, CRESST, COGeNT, CDMS II ßà XENON100, XENON10, EDELWEISS Discrepancy gets more serious if we take new quenching factor measurements
New data from LUX, DarkSide, KIMS-NaI are expected soon !
Not consistent ! à Do we have multiple components in DM ?
Hope to see the solution soon.
28LUX (Large Underground Xenon) experiment
§ Total 370kg LXe, D=47cm, H=48cm à 250 kg.§ 118kg, 85.3 days run à 10065 kg days
85.3 days data (27.6 kg year)
Not significant events in nuclear recoil region !!CDMS three event ~ 1000 events here.
XENON100
LUX contradicts all low mass claims !! à Does this mean all the low mass signals are rejected ?
32New quenching Factors – Caution !
Recently, the quenching factors are remeasured for NaI(Tl), LXe, CsI(Tl). New measurements are significantly different from the previous measurements.
NaI(Tl)
DAMA region moves !
Phys.Rev. C88 (2013) 035806
34
KIMS+ Projects @ CUP
I. KIMS-CsI : Upgrade of CsI(Tl) crystal detector§ Lower threshold ~ 1.5keV, <1dru, counts/(keV kg day).
§ This will help to clear issues about the modulation signals of DAMA.
II. KIMS-NaI : new NaI(Tl) detector• Duplicate DAMA experiment with ultra-low background NaI(Tl) crystals.
• 200kg run in 2015-2016
III. KIMS-LT§ natCanatMoO4 crystals ~ 200 kg year.
§ High sensitivity in low mass WIMP.
§ 2019-2022
10-5 /(keV kg day) with light sensor5 keV threshold.
I. KIMS-CsI : Upgrade of CsI(Tl) crystal detector§ Lower threshold ~ 1.5keV, <1dru, counts/(keV kg day).
§ This will help to clear issues about the modulation signals of DAMA.
II. KIMS-NaI : new NaI(Tl) detector• Duplicate DAMA experiment with ultra-low background NaI(Tl) crystals.
• 200kg run in 2015-2016
III. KIMS-LT§ natCanatMoO4 crystals ~ 200 kg year.
§ High sensitivity in low mass WIMP.
§ 2019-2022
CUP (Center for Underground Physics)at Institute for Basic Science (IBS) formed to support DM and DBD experiments. New underground Lab with ~ 1400m depth is under preparation.
10-5 /(keV kg day) with light sensor5 keV threshold.
35KIMS-NaI ExperimentNaI(Tl) Crystal
CsI Detector
• Direct check for DAMA is necessary even with LUX data.
• NaI(Tl) 200kg exp at CUP.• 2013 : 2 crystals.
DAQ Time : 5.2 daysCsI Detector DAQ Time : 5.2 days
~ 3 dru
DAMA ~ 1druPurification à <1 dru
Activation x-ray + 40K
36
Summary & Sensitivities of KIMS+
CoGent CRESST
KIMS upgrade
KIMS-LT
XENON1T
CDMS
XENONSuperCDMS
Buchmuelleret al.
Trotta et al.
WIMP Mass (GeV/c2)
37
<2013 KRISS>
0.7keV FWHM for 60keV g
1.2keV FWHM for 5.5MeV a
Am241 full spectrum MMC with gold foil absorberwith C ~ 0.3kg CaMoO4
<2013 KRISS>
Phonon collectorPatterned gold film
MMC
Low temperature detector development @ CUP
Gold film
Gold wires(thermal connection)
s E / E = 0.1% @Qvalue
1.6 keV signal @ 10 mK
39SuperCDMS
39
9 kg of Ge arranged in 5 towers (15 iZIPs), Running now! +2V charge
0V phonon
0V phonon-2V charge
Ge
(a) X [mm]Z
[mm
]−2 −1 0 1 2
0
1
2
0V -2V 0V 0V-2V
(b)
phonon
charge
(c)
+2V charge0V phonon
0V phonon-2V charge
Ge
(a) X [mm]Z
[mm
]−2 −1 0 1 2
0
1
2
0V -2V 0V 0V-2V
(b)
phonon
charge
(c)
§ Phonon and charge sensors on both sides§ Surface events : charge on one face§ Thickness of Ge crystals : 1cm è2.5 cm § Mass : 0.25 kg è 0.6 kg § <0.6 expected leaked events in 4 years wi
th 200 kg Ge at SNOLAB!
arXiv:1305.2405
43Conclusions
l Low mass WIMPs issue including DAMA will be cleared with more experiments including KIMS-NaI.
l Deep underground experiments complement the expensive accelerator experiments for DM search.
l Extreme techniques such as lower threshold & background, higher resolution, and more massive detectors, keep emerging for difficult tasks.
l 10-48 cm2 for WIMP-nucleon cross section can be reached in ~ 7 years.
l Low mass WIMPs issue including DAMA will be cleared with more experiments including KIMS-NaI.
l Deep underground experiments complement the expensive accelerator experiments for DM search.
l Extreme techniques such as lower threshold & background, higher resolution, and more massive detectors, keep emerging for difficult tasks.
l 10-48 cm2 for WIMP-nucleon cross section can be reached in ~ 7 years.
45SuperCDMS
45
9 kg of Ge arranged in 5 towers (15 iZIPs), Running now! +2V charge
0V phonon
0V phonon-2V charge
Ge
(a) X [mm]Z
[mm
]−2 −1 0 1 2
0
1
2
0V -2V 0V 0V-2V
(b)
phonon
charge
(c)
+2V charge0V phonon
0V phonon-2V charge
Ge
(a) X [mm]Z
[mm
]−2 −1 0 1 2
0
1
2
0V -2V 0V 0V-2V
(b)
phonon
charge
(c)
§ Phonon and charge sensors on both sides§ Surface events : charge on one face§ Thickness of Ge crystals : 1cm è2.5 cm § Mass : 0.25 kg è 0.6 kg § <0.6 expected leaked events in 4 years wi
th 200 kg Ge at SNOLAB!
arXiv:1305.2405
49Observations for last 100 years confirm Dark Matter.
rWIMP (r) ~ 0.3GeV / cm3
in solar system
1E0657-558 Merging ClusterEqui-Density line from Lensing Effect
“A direct Empirical Proof of the Existence of Dark Matter” by Clowe et al.
X-ray intensity from ChandraObserver (Intergalactic Plasma)
First observation of separated Dark Matter from baryons.
50Phonon measurement with Low temperature detectors
Energy absorption è Temperature increase
Absorber
Thermometer
Thermal link
Choice of thermometers• Thermistors (NTD Ge, doped Si)• TES (Transition Edge Sensor)• MMC (Metallic Magnetic Calorimeter )
Heat sink < 1 K
crystal
MMC
51Surface Event Rejection
• Ionization yield (phonon/ionization) is ~1 for background.
• Nuclear Recoil(WIMP) ~ 0.3
• Combination of yield and “timing” cuts rejects vast majority of background
Loer, WIN 2013
surface event
Nuclearrecoil
rising edge slope
Loer, WIN 2013
52Indirect searches challenge direct exp.
PRL 110, 131302 (2013)PRL 110, 131302 (2013)
AMS-02
PRL 110, 141102 (2013)
55New PMTs enhances DM search in scintillating detectors
XMASS single phase LXe detector14.7 p.e./keV
16.1(0.66) p.e./keV (ANAIS)15.4 p.e./keV (KIMS-NaI)
ANAIS & KIMS-NaI crystals from “Alpha Spectra” coupled with SBA PMTs.