1. Sun Kee Kim Seoul National University
Underground Experiments in Korea
Sun Kee Kim
Seoul National University
ASK 2011
April 11-12, 2011, Seoul

2. Questions on our Universe
What is the Universe made of?
How big is the Universe?
How did the Universe begin?
What is the destiny of the Universe?
What is the meaning of life in the Universe? …
Some of these questions may be answered
by understanding the nature of Dark matter
and Neutrinos
“The most incomprehensible thing about the world is that it is comprehensible”
- A. Einstein -

3. Standard Model of Elementary Particles
Quarks and leptons : Spin 1/2
Gauge Bosons
Spin 1 :
Spin 2 :
Higgs Bosons : Spin 0
properties are not understood very well
expected to be discovered at LHC
Great achievement with partcile accelerators during the last century !

4. Composition of our Universe
Mostly Dark …

5. Existence of dark matter by astronomical observations
In 1933, Zwicky observed that the rotational speed of galaxies in a cluster of galaxies (Coma cluster) too fast to be explained by mass of galaxies in the cluster
Gravitational lensing by cluster of galaxies
Collision of galaxy clusters
Rotation curves of galaxies
Cosmic Microwave Background
Density of dark matter around the sun ~ 0.3 GeV /cm3
~ 5 x kg/cm3

6. First idea of WIMP in 1977
by B.W.Lee and S. Weinberg

7. WIMP LSP in SUSY  Excellent CDM candidate Relic abundance
(Weakly Interacting Massive Particles)
Relic abundance
Annihilation cross section of a particle with a weak scale
interaction
 Excellent CDM candidate
LSP in SUSY

8. Elastic scattering of SUSY WIMP with ordinary nucleus
Spin Dependent Interaction
Spin Independent Interaction
XLIIInd Rencontres de MORIOND Sun Kee Kim, Seoul National University

9. Elastic Sacttering of WIMP off a nuclues in the detector
Direct Search for WIMP
Elastic Sacttering of WIMP off a nuclues in the detector
WIMP
Recoiled nucleus
Recoil energy < 100 keV
Expected event rate
<1/kg/day or less
R : event rate
R0: total event rate
E0: most probable incident kinematic energy
r : kinematic factor, 4MwMN/(MW+MN)2

10. DAMA Annual Modulation
Status of WIMP search
vsun=232km/s
sun
earth
vorbit=30km/s
=60o
DAMA Annual Modulation
2-6 keV
A=(0.0129±0.0016) cpd/kg/keV
2/dof = 54.3/  C.L.
Fit :Acos[w(t-t0)]

11. Neutrino mass and mixing
measurable by neutrino oscillation
needs to be measured
DayaBay, DCHOOZ, RENO
needs to be measured

12. Neutrinoless Double Beta Decay
Transition bb
allowed
Forbidden  transition Z
Energy
Z+1
Z+2
Qbb
100Mo
100Ru
100Tc
0νββ decay occurs
when mν≠0 and ν = ν

13. Status of DBD searches Positive signature? 100 meV 25 meV 2meV
need 1 ton detector

14. Challenges for Rare Processes
Dark Matter (Direct detection of WIMP)
Very weak interactions with ordinary matter : Rare
Very low energy signals
Large background
Nuclear recoil vs electron recoils
Neutrinoless Double Beta Decay Search
Life time is expected to be very long : Rare
2νββ vs 0νββ Self background
These searches cannot be performed
without an Underground Laboratory
without an excellent detector performance

15. Why underground Laboratory ?
Cosmic ray 106eV ~ 1020eV, p, He,…
Nuclear interaction - secondary particles
1 muon /second/10 cm x 10 cm at sea level
Muon interaction creates neutrons
Neutron
- mimic WIMP signal
- generate radioactive isotopes
Neutrons from rocks can be avoided by a proper shielding
But, if muons interact within the shield, neutrons can enter the detector
Need to reduce the muon flux as much as possible
Deep underground experimental site

16. Underground Laboratories
Sudbury
PICASSO
Boulby Mine
NAIAD
ZEPLIN
DRIFT
Soudan Mine
CDMS
COUPP
Canfrane
ANAIS
IGEX
Frejus
EDELWEISS
Super NEMO
Gran Sasso
DAMA, LIBRA
XENON, CRESST
CUORE, GERDA
Kamioka
XMASS
Suchiwan
ULGe
Xenon
Yangyang
KIMS
AMORE

17. Yangyang Underground Laboratory(Y2L)

18. Yangyang Underground Laboratory
Korea Middleland Power Co.
Yangyang Pumped Storage Power Plant
(Upper Dam)
(Power Plant)
(Lower Dam)
Construction of Lab. buildings done in 2003
Minimum depth : 700 m / Access to the lab by car (~2km)

19. KIMS(Korea Invisible Mass Search) collaboration
H.C.Bhang, J.H.Choi, S.C.Kim, S.K.Kim
J.H.Lee, M.J.Lee, S.J.Lee, S.S.Myung
Seoul National University
U.G.Kang, Y.D.Kim, J.I. Lee
Sejong University
H.J.Kim, J.H.So, S.C.Yang
Kyungpook National University
M.J.Hwang, Y.J.Kwon
Yonsei University
I.S.Hahn
Ewha Womans University
Y.H.Kim, K.B.Lee, M. Lee
Korea Research Institute of Standard Sciences
J.Li
Institute of High Energy Physics
Y.Li, Q.Yue
Tsinghua University

20. KIMS research program Dark Matter Search CsI(Tl) crystal detector
An intermediate result was published (2007)
100 kg array running
Neutrinoless Double Beta Decay Search
Metal loaded liquid scintillator
HPGe detector + CsI(Tl) crystal + Sn, Zn,..
to excited states, beta+ decays
CaMoO4 crystal
- scintillation technique
- cryogenic technique

21. WIMP search with CsI(Tl) Crystals
Easy to get large mass with an affordable cost
 Good for AM study
High light yield ~60,000/MeV
Pulse shape discrimination
 Moderate background rejection
Easy fabrication and handling
Cs-133, I-127 (SI cross section ~ A2)
Both Cs-133, I-127 are sensitive to SD interaction
electron recoil
Isotope J
Abun
<Sp>
<Sn>
133Cs
7/2
100%
-0.370
0.003
127I
5/2
0.309
0.075
73Ge
9/2
7.8%
0.03
0.38
129Xe
1/2
26%
0.028
0.359
131Xe
3/2
21%
-0.009
-0.227
nuclear recoil

22. KIMS(Korea Invisible Mass Search)
DM search experiment with CsI crystal
CsI(Tl) Crystal 8x8x30 cm3 (8.7 kg)
3” PMT (9269QA) : Quartz window, RbCs photo cathode
~5 Photo-electron/keV

23. WIMP search limit with 4 crystals
PRL 99, (2007)
Nuclear recoil of 127I of DAMA signal region is ruled out unambiguiously
Most stringent limit on SD(pure proton) interactions

24. Data taking with 12 crystals Total exposure: 32793 kg days
12 crystals(104.4kg) running (from 2008)
Stable data taking for more than a year
Unique experiment to test DAMA annual modulation
CsI DAQ rate < 6 Hz
Sep ~ Aug. 2010
Total exposure: kg days

25. Am-241 Energy Calibration
Am calibration
-> ~5 p.e /keV
13.9keV Np L X-ray
17.8keV Np L X-ray
20.8keV Np L X-ray
26.35keV gamma
Cs, I X –ray escape
gamma
Relative intensity.....
E(keV)

26. High energy tail events rejection
5us
Additional cut: Muon veto, file up rejection, trigger
condition cut, multiple hit rejection

27. NR event rate estimation
Modeling of Calibration data with asymmetric gaussian function n g
Electron recoil
Nuclear recoil
Best fit
Fit the WIMP search DATA with PDF function from gamma and neutron calibration data
 extract NR events rate 27

28. Surface alpha (SA) events background
222Rn progenies produce this background.

29. Sides are wrapped by teflon
Study of SA events
with Rn progeny contaminated crystal
Aluminum foil
t=2um x 3 layers A B
Sides are wrapped by teflon
CsI(Tl) crystals
A: Rn progeny contaminated
-exposed to Rn gas
for one week
B: clean
Background
Surface alpha events
mean time(mt)
Tagged as
Alpha at part B
E(keV)

30. The logrmt10 distribution for various types of particle
PSD parameter
neutron SA
gammas
in 10s

31. Modeling WIMP search data with 3 components, SA, NR, gamma
3keV
4keV
det0
5keV
6keV SA
NR(WIMP)
gamma
7keV
8keV
9keV
10keV

32. Determination of the 90 % C.L. limit of NR event rates
Pdf = f0 x FNR + f1 x FSA + (1-f0-f1) x Fgamma
The posterior pdf of f0 & f1 are obtained
from Bayesian analysis method.

33. NR events rate for det0 to det12
Counts/day/kg/keV
preliminary
Determined from
Bayesian method
90% limit
68% interval
3-11 keV

34. KIMS WIMP search
Spin Independent
Spin Dependent
preliminary

35. Plan on Annual Modulation Stuudy
Taking data for more than 18 months  2 year data by this summer
Sep ~ Feb. 2011
~ 3 counts/day/kg/keV

36. DBD Searches at KIMS Passive targets : HPGe + CsI(Tl) Active targets
[Nuclear Physics A 793 (2007)]
64Zn EC+b+ decay
124Sn bb to excited states of 124Te
122Sn EC+b+ decay
Active targets
124Sn 0νbb : Sn loaded Liquid scintillator
[Astropart. Phys. 31,412 (2009)]
84Sr EC+b+ decay : SrCl2 crystal
92Mo EC+b+ decay : CanatMoO4 crystal
100Mo 0νbb decay : Ca100MoO4 crystal
R&D effort is on going  birth of AMORE

37. β+EC decay of 92Mo 92Mo nucleus is double EC and beta plus EC isotope
511keV γ
Gamma detector
Active crystal
with 92Mo
Conceptual setup
Mo-92 nucleus is double EC and beta plus EC isotope.
And This is double beta decay scheme from mo-92 to Zr-92.
Q-value of the double EC is 1650keV and EC beta plus is 628keV.
If camoo4 crystal is used for mo-92 decay, we can use the triple coincidence with the 628keV of the camoo4 and 511keV in 2 CsI crystals.
So you can see here the conceptual setup.
If the positron stops inside camoo4 crystal, then two 511keV gammas emit b2b direction.
The abundance of Mo-92 is 14.84%.
92Mo nucleus is double EC and beta plus EC isotope
EC/β+ Q-value=627keV, ECEC = 1,650keV
Abundance = 92Mo: 14.84%, 100Mo: 9.63%
e+ stops in active(CaMoO4) Crystal.

38. β+EC decay of 92Mo T1/2 > 2.3 x 1020y (90% CL) Paper in preparation
PMTs & CsI crystals are crossly connected.
Lead shielding(10 cm)
CaMoO4 is surrounded by 14 CsI crystals
U - CsI(Tl) crystals
Th - CsI(Tl) crystals
K – 1inch PMT
K – CsI(Tl) crystals
K – CaMoO4 crystal
This is a picture of detector setup at the y2l underground lab in korea.
Here photos are before and after attachment of the pmt. And lead shielding is 10cm.
Camoo4 is located in the center of the cavity and 14 csi detector array. And 511keV gammas are in opposite direction.
We are using b2b coincidence condition.
There are 12 csi crystals with a size….
And 2 of this crystals are coupled together and attached to pmt.
The total mass of camoo4 crystal is 255g.
T1/2 > 2.3 x 1020y (90% CL)
Paper in preparation

39. New HPGe detector at Y2L ~527 cc ~2.8kg Energy Resolution
Will be used for
- Measurement of internal background
- DBD search with beta+
~527 cc
~2.8kg
Co60/Cs137/Ba133
Energy Resolution

40. CaMoO4 for ββ CaMoO4 DBD for Mo-100 (3034 keV), Ca-48(4272 keV)
high energy  less background
Mo-100 enrichment >90% not so difficult
for Mo-100 search, Ca-48 need to be depleted
Scintillator at room temp; 10-20% of CsI(Tl) at 20o
increases at lower temp.
Decay time ; 16 μ sec
Wavelength; ns-> RbCs PMT or APD
Can be used as cryogenic detector (absorber) Z
Energy
Z+1
Z+2
Qbb
100Mo
100Ru
100Tc
resolution
Compton edge
CaMoO4 + LAAPD at -159oC

41. 40Ca100MoO4 Mo-100 2nβ Ca-48 Depletion needed
First 40Ca100MoO4 crystal
after big bang
Mo-100 2nβ
Ca-48 2nββ
Signal (m=0.4eV)
Bi-214
Tl-208
SB28
CMO-3
S35
D44 mmxL51mm~300g

42. 1 keV energy deposit : ~ 60 photons (CsI(Tl)) , ~280 e-h pairs (Si)
Cryogenic Detector
Advantages of using cryogenic calorimeters
High energy resolution (ΔE/E < 1/1000)
Ultra low energy threshold ( < 1 eV)
Simultaneous readout of Charge or Light
 discrimination of particle type (e, alpha, nuclear recoils)
e-h pair production : 3.6 eV in Si, 2.9 eV in Ge ( *kT (T=0.1K)~10 μeV)
(BG 1.11 eV in Si, 0.67eV in Ge) 2/3 energy goes to phonons…
For nuclear recoil ~10% goes to ionization
1 keV energy deposit : ~ 60 photons (CsI(Tl)) , ~280 e-h pairs (Si)

43. Energy absorption  Heat (Temperature)
Cryogenic Detector
Energy absorption  Heat (Temperature)
Absorber
Thermometer
Thermal link
Heat sink < 100 mK
, , , etc.
Choice of thermometers
Thermistors (doped Ge, Si)
TES (Transition Edge Sensor)
MMC (Metallic Magnetic Calorimeter )
STJ, KID etc.
Example

44. Metallic Magnetic Calorimeter (MMC)
Field coil
Magnetic material (Au:Er) in dc SQUID
Au:Er(10~1000ppm)
paramagnetic system
metallic host: fast thermalization ( ~ 1ms)
Can control heat capacity by magnetic field
junctions
5 mT  Δε = 1.5 eV
1 keV  109 spin flips
g = 6.8
U. of Heidelberg 44

45. Experimental setup at KRISS with MMC
~ 500 m thick brass
crystal size
~ 1 cm  0.7 cm  0.6 cm
base temperature : 13 ~ 100 mK 45

46. Performance of CMO+MMC
Astroparticle Physics, 2011
5.5 MeV alpha
FWHM = 11.2 keV
high energy resolution
suitable to search for Mo-100 0νββ
Emission line of Mo : 18keV
42 keV
FWHM = 1.7 keV
60keV gamma
low energy threshold
suitable to search for WIMP

47. Scintillation technique
CaMoO4 DBD Sensitivity
Scintillation technique
5% FWHM resolution
Cryogenic detector
0.5% FWHM 15 keV FWHM
5 years, 100 kg 40Ca100MoO4
7.0x1026 years -> 20 – 70 meV

48. Dark matter sensitivity of CaMoO4 cryogenic experiment
Bottino et al
Trotta et al
Ellis et al
CaMoO4
CDMS 2008
SuperCDMS 25kg
XENON
XENON kgd
CMSSM, Ellis et al
CMSSM, Markov chain Trotta et al
Effective MSSM, Bottino et al
Eth=10 keV
(5 and 100 kg year)
Eth=1 keV

49. AMoRE Collaboration 4 countries 8 institutions 69 collaborators
Korea (39)
Seoul National University : H.Bhang, S.Choi, M.J.Kim, S.K.Kim, M.J.Lee, S.S.Myung, S.Olsen, Y. Sato, K.Tanida, S.C.Kim, J.Choi, S.J.Lee, J.H.Lee, J.K.Lee, H.Kang, H.K.Kang, Y.Oh, S.J.Kim, E.H.Kim, K.Tshoo, D.K.Kim, X.Li, J.Li, H.S.Lee (24)
Sejong University : Y.D.Kim, E.-J.Jeon, K. Ma, J.I.Lee, W.Kang, J.Hwa (5)
Kyungpook national University : H.J.Kim, J.So, Gul Rooh, Y.S.Hwang(4)
KRISS : Y.H.Kim, M.K.Lee, H.S.Park, J.H.Kim, J.M.Lee, K.B.Lee (6)
Russia (16)
ITEP(Institute for Theoretical and Experimental Physics) : V.Kornoukhov, P. Ploz, N.Khanbekov (3)
Baksan National Observatory : A.Ganggapshev, A.Gezhaev, V.Gurentsov, V.Kuzminov, V.Kazalov, O.Mineev, S.Panasenko, S.Ratkevich, A.Verensnikova, S.Yakimenko, N.Yershov, K.Efendiev, Y.Gabriljuk (13)
Ukraine(11)
INR(Institute for Nuclear Research) : F.Danevich, V.Tretyak, V.Kobychev, A.Nikolaiko, D.Poda, R.Boiko, R.Podviianiuk, S.Nagorny, O.Polischuk, V.Kudovbenko, D.Chernyak(11)
China(3)
Tsinghua University : J.Li, Y.Li, Q.Yue(3)
4 countries
8 institutions
69 collaborators

50. 국가대형연구시설구축지도(National Facility Road Map (NFRM))
21개 S군에 선정됨 (NFRM에는 282 제안 중 69 선정, 69개는 다시 S,A,B군으로 분류)

51. SUMMARY KIMS :Results using 3409 kg days data (PRL 99, 091301 (2007))
100 kg crystals installed in the shield and data taking is on going
 PSD result shown today
 Annual modulation study in progress
DBD searches in various isotopes : Zn-64, Sn-124, Sn-122, Mo-92, Sr-84
 Some best limits
Competitive DBD search using CaMoO4 crystals can be realized rather soon  A new collaboration AMORE was formed

52. Thank you

53. Channeling  Practically lower the trehsold
Well known technology to bend particle beam with crystal.
Studied a lot in 1960s
Quenching is expected to be less
PSD may not work?
Less studied for low energy ions.
 Practically lower the trehsold
Na recoil
I recoil
Orange: w/o channeling
Savage, Gelmini, Gondolo and Freese, arXiv
Green: w/ channeling
When channeling is accounted, I recoil is preferred  better chance for KIMS
But, because of Blocking, the effect of channeling might be smaller than DAMA Claimed

54. Channeling Understanding Quenching factorbetter is important.
Plan to measure quenching factor and channeling effect using a neutron setup
Also simulation study is on going together
CsI(Tl) Q.F
NaI(Tl) Q.F