1. Center for Underground Physics, IBS
Dark MAtters and Neutrino Projects at the Center for Underground Physics.
Yeongduk Kim
Center for Underground Physics, IBS
Sejong University
AKPA

2. Center for Underground Physics (CUP)
CUP began on July 2013 as a headquarter center.
Now, 17 Ph.Ds, 15 students, 3 technicians, 2 administrations.
Research Area : Dark Matter, Double Beta Decay, Sterile neutrino search, Low temperature Detector Development.

3. Evidences for Dark Matter Existence

4. More quantitative evidence : cosmic microwave background

5. Particle candidates Many particle candidates
are proposed with many orders of magnitude of mass.
Who will be the hero ? Or
None of them.
K.Y. Choi, JKPS 63, 1685(2013)

6. Weakly Interacting Massive Particle (WIMP)
increasing
WIMP is a massive new particle having a right <sv> value for the current dark matter density. So it is a good candidate for dark matter particles.

7. WIMP DETECTION c q (Accelerator Search) Production (Indirect Search)
Annihilation
WIMP scattering
(Direct Search)

8. Detection Principle of Direct Search
Detector
WIMP
Nucleus
WIMP-Nucleus elastic scattering
Event rate :
Experiment
Measure this
SUSY models
Limit of R  Limit of s

9. What is the direct signal for WIMPs ?
Recoil energy spectrum as expected at low energy.
Annual modulation.
Directional asymmetry.
A2 dependence (Spin-independent)
Yearly revolution  annual modulation
Daily rotation  direction change
Earth velocity (30km/s)

10. DAMA/LIBRA experiment
250 kg NaI(Tl) crystals coupled with PMTs.
Observed clear annual modulation for 13 years.
PMT
+HV
divider

11. Status of WIMP searches

12. YangYang(Y2L) Underground Laboratory
(Upper Dam)
YangYang Pumped
Storage Power Plant
Seoul
Y2L
1000m
700m
RENO
(Power Plant)
(Lower Dam)
KIMS (Dark Matter Search)
AMoRE (Double Beta Decay Experiment)
Minimum depth : 700 m / Access to the lab by car (~2km)

13. KIMS-NaI Experiment @ CUP
To verify the DAMA result using same NaI(Tl) crystals.
Our strategy : Achieve lower background level and lower energy
threshold than DAMA by factor 2.
We can clarify the origin of the annual modulation unambiguously.
NaI(Tl) Crystal
CsI Detector

14. Background rates – We are getting there.
Low threshold down to 1 keV is possible.
Background reduction expected by further purification.

15. Search for Neutrinoless Double Beta Decays
Ettore Majorana (1906 – 1938 ?)

16. Neutrino mixing & oscillation
If neutrinos are massive and mixed, then they oscillate.

17. Neutrino mixing & oscillation
Survival Probability
PRL100, (2008)

18. Search for Neutrinoless double beta decay (0nbb)
event
Observation of 0nbb will prove

19. Neutrino mass from 0nbb experiment
Half-lifves of 0nbb inversely proportional to mass2
Half-life
Measured
Neutrino
Mass

20. Elliott & Vogel, Ann, Phys. (2002)
Moore’s law for 0nbb ?
Elliott & Vogel, Ann, Phys.
(2002)
76Ge, Gerda (0.3)
136Xe, EXO (0.26)
136Xe, KAMLAND-ZEN (0.19)

21. Overview of AMoRE-200kg Scintillating Bolometer : 40Ca100MoO4 + MMC
Light sensor
MMC
phonon
sensor
<10-50 mK>
216 g
<2018>
<Now, 2013>
AMoRE-200 is the most massive experiment with enriched isotope having Q value > 3MeV.

22. MMC (Metallic Magnetic Calorimeter)
paramagnetic sensor:
Au:Er 수정
Mass 수정 216g

23. Energy resolution data
CaMoO4(natural) with a phonon sensor only.
<2013 KRISS>
FWHM = 9 keV, Goal = 5 keV

24. Crystal Growing Facility
Motivation : difficulty to find a reliable and economical company.
Will develop chemical purification and crystallization ourself inside the center. (4 furnaces)

25. Races for 0nbb

26. Thank you !

27. Underground Lab Preparation Team
Organization of CUP
Dark Matter Group
New Detector Group
Low Temp. Detector Group
Double Beta Decay Group
Nuclear Astrophysics Group
Director
Y2L
KT1 LAB
Simulation Team
SBL Team
KIMS-NaI Team
Advisory Committee
Underground Lab Preparation Team
Administration
KRISS
Samcheok City
KIMS Collaboration
New Physics Team
Adjunct group
AMoRE Collaboration

28. Weakly Interacting Massive Particles (WIMP)
이휘소, 와인버거 박사의 1977 논문
“Cosmological Lower Bound on Heavy-Neutrino Mass” (무거운 중성미자 질량에 대한 우주론적인 하한값)
암흑물질의 후보로서의 약하게 상호작용하는 윔프와 같은 무거운 입자의 가능성을 거론.
빅뱅이후 약하게 상호작용하는 안정적인 입자가 생성되어 Freeze out 되어 남게 되면 Dark Matter가 될수 있다.
M(wimp)>2GeV

29. KIMS-CsI annual modulation data
2 Jun.
Time
Background Level
12 crystals (104.4kg).
2.5 year data (Sep. 2009–Feb. 2012)
Background Level : 2~3 cpd/kg/keV
The mean amplitude from 3 keV to 6 keV is ± cpd/kg/keV

31. Comparison with Direct Search

32. PMT noise reduction in background data.
DAMA/LIBRA reported PMT noise reduction by introducing charge ratio parameters. KIMS-NaI obtained the same results as DAMA. X1 X2
DAMA, E=2-4 keV
KIMS-NaI, E=2-4 keV
PMT noise
Real signals

33. Supersymmetric particles
Q|fermion> = |boson>
particle  super particle
R parity = 1 for ordinary particles
= -1 for SUSY partners
If R parity is conserved, LSP ( Lightest SUSY Partner) will be stable and a strong candidate of WIMP.

34. Toward lower neutrino mass
AMoRE 10
AMoRE 200
Effective Neutrino mass (eV)
Lightest neutrino mass (eV)
Toward lower neutrino mass

35. Pulse Shape Discrimination
 and  events show different pulse shapes in phonon signals.
Beta-Alpha
Gamma
Muon
Alpha

36. Phonon sensor for AMoRE
MMC
Phonon collector
Patterned gold film
Gold film
Gold wires
(thermal connection)
216 g CaMoO4
rise-time: ~ 0.5ms
We measure both thermal and athermal phonons.
<Heat flow optimization>