DARK MATTERS AND NEUTRINO PROJECTS AT
THE CENTER FOR UNDERGROUND PHYSICS.
Yeongduk Kim
Center for Underground Physics, IBS
Sejong University
2014. 5. 9.
AKPA
Center for Underground Physics (CUP)
2
 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.
Evidences for Dark Matter Existence
3
More quantitative evidence : cosmic microwave background
4
Particle candidates
5
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)
Weakly Interacting Massive Particle (WIMP)
6
Annhilation process : cc ® qq,...
s Au 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.
WIMP DETECTION
c
c
q
q
Annihilation
(Indirect Search)
WIMP
cc ® qq(hadrons),
e +e - , m +m - , t +t - ,nn
®W +W - , ZZ
® gg
® Zg
WIMP scattering
(Direct Search)
c  N ucleus  c  N ucleus
Production
(Accelerator Search)
7
Detection Principle of Direct Search
8
WIMP  0 , M W ,  D
R µ fWIMP N DETECTORs
Detector
Nucleus A,Mass, E
SI (SD)
WA
R
WIMP-Nucleus elastic scattering
Event rate :
Experiment
Measure this
SUSY models
Limit of R  Limit of s
s WN
MW
What is the direct signal for WIMPs ?
9
1.
2.
3.
4.
Recoil energy spectrum as expected at low energy.
Annual modulation.
Directional asymmetry.
A2 dependence (Spin-independent)
Yearly revolution  annual modulation
Earth velocity (30km/s)
Daily rotation  direction change
DAMA/LIBRA experiment
10
250 kg NaI(Tl) crystals coupled with PMTs.
Observed clear annual modulation for 13 years.
PMT
+HV
divider
Status of WIMP searches
11
YangYang(Y2L) Underground Laboratory
(Upper Dam)
YangYang Pumped
Storage Power Plant
Y2L
Seoul
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)
KIMS-NaI Experiment @ CUP
13
• 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
Background rates – We are getting there.
14
• Low threshold down to 1 keV is possible.
• Background reduction expected by further purification.
Search for Neutrinoless Double Beta Decays
Ettore Majorana (1906 – 1938 ?)
Neutrino mixing & oscillation
16
If neutrinos are massive and mixed, then they oscillate.
ne n
nm
n
e
m
nt
n
t
 32
m
m
Dm122 = 7.48´10-5 eV 2
1
Dm322 = 2.4´10-3 eV 2
Dm322 = 2.4´10-3 eV 2
2
 13
00
16
Dm122 = 7.8´10-5 eV 2
m =?
m3 ?
1
Neutrino mixing & oscillation
17
Survival Probability
P           
2
t

L ( km ) 
2
2
2
2
2
 1  sin 2 sin  1.27   m ( eV )
,

m

m

m

2
1
E
(
G
eV
)



2
2
PRL100, 221803 (2008)
17
sin 2 2q
Search for Neutrinoless double beta decay (0bb)
18

b b

Observation of 0bb will prove
n =n
0bb
event
Neutrino mass from 0bb experiment
19
Half-lifves of 0bb inversely proportional to mass2
æm ö
éT 0n ù µ ç bb ÷
ë 1/2 û ç m ÷
è e ø
Half-life
-1
2
Neutrino
Mass
Measured
mbb =U m1 +U m2 +U m3
2
e1
0n
1/2
T
2
e2
® mbb ® m1(3)?
2
e3
Moore’s law for 0bb ?
Elliott & Vogel, Ann, Phys.
(2002)
T1/20n > 2.1´1025 years
76Ge,
136Xe,
136Xe,
Gerda (0.3) 2013.9
EXO (0.26) 2012.7
KAMLAND-ZEN (0.19) 2013.2
Overview of AMoRE-200kg
21
Scintillating Bolometer :
MMC
40Ca100MoO
4
+ MMC
Light sensor
CaMoO4
216 g
<Now, 2013>
MMC
phonon
sensor
<2018>
<10-50 mK>
AMoRE-200 is the most massive experiment with
enriched isotope having Q value > 3MeV.
MMC (Metallic Magnetic Calorimeter)
22
paramagnetic sensor:
Au:Er
Energy resolution data
23
CaMoO4(natural) with a phonon sensor only.
<2013 KRISS>
FWHM = 9 keV,
Goal = 5 keV
Crystal Growing Facility
24
Motivation : difficulty to find a reliable and economical company.
Will develop chemical purification and crystallization ourself
inside the center. (4 furnaces)
Races for 0bb
25
Thank you !
Organization of CUP
27
Administration
Director
Advisory Committee
Y2L
KIMS Collaboration
New Detector Group
Nuclear Astrophysics Group
Low Temp. Detector Group
Double Beta Decay Group
Dark Matter Group
AMoRE Collaboration
KT1 LAB
KRISS
Simulation Team
SBL Team
KIMS-NaI Team
Adjunct group
Underground Lab
Preparation Team
Samcheok City
New Physics Team
Weakly Interacting Massive Particles (WIMP)
28
이휘소, 와인버거 박사의 1977 논문
“Cosmological Lower Bound on Heavy-Neutrino
Mass” (무거운 중성미자 질량에 대한 우주론적인 하한값)
암흑물질의 후보로서의 약하게 상호작용하는 윔프와 같
은 무거운 입자의 가능성을 거론.
빅뱅이후 약하게 상호작용
하는 안정적인 입자가 생
성되어 Freeze out 되어
남게 되면 Dark Matter가
될수 있다.
M(wimp)>2GeV
KIMS-CsI annual modulation data
29
Background Level
2 Jun.
• 12 crystals (104.4kg).
• 2.5 year data (Sep. 2009–Feb. 2012)
• Background Level : 2~3 cpd/kg/keV
Time
 The mean amplitude from 3 keV to 6 keV is
0.0008±0.0068 cpd/kg/keV
Comparison with Direct Search
31
PMT noise reduction in background data.
32
DAMA/LIBRA reported PMT noise reduction by introducing charge ratio
parameters. KIMS-NaI obtained the same results as DAMA.
Area(100 £ t £ 600ns)
Area(0 £ t £ 50ns)
X1 =
, X2 =
Area(0 £ t £ 600ns)
Area(0 £ t £ 600ns)
DAMA, E=2-4 keV
KIMS-NaI, E=2-4 keV
PMT noise
Real signals
X2
X1
X2
X1
Supersymmetric particles
33
Q|fermion> = |boson>
particle  super particle
R parity = 1 for ordinary particles
= -1 for SUSY partners
R  (  1)
2 j3B  L
If R parity is conserved, LSP ( Lightest SUSY Partner)
will be stable and a strong candidate of WIMP.
(eV)
Effective Neutrino mass
AMoRE 200
Lightest neutrino mass (eV)
Toward lower neutrino mass
AMoRE 10
Pulse Shape Discrimination
35
 and b events show different pulse shapes in phonon signals.
Beta-Alpha
Gamma
Muon
Alpha
Phonon sensor for AMoRE
36
Phonon collector
Patterned gold film
MMC
Gold film
216 g CaMoO4
Gold wires
(thermal connection)
rise-time: ~ 0.5ms
We measure both thermal
and athermal phonons.
<Heat flow optimization>