DARK MATTERS AND NEUTRINO PROJECTS AT THE CENTER FOR

UNDERGROUND PHYSICS.

AKPA

Yeongduk KimCenter for Underground Physics, IBS

Sejong University

2014. 5. 9.

2Center 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.

3Evidences for Dark Matter Existence

4

More quantitative evidence : cosmic microwave background

5Particle 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)

6Weakly Interacting Massive Particle (WIMP)

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.

increasing

7WIMP DETECTION

c c

q q

Annihilation

(Indirect Search)

WIMP scattering(Direct Search)

Pro

duct

ion

(Acc

eler

ator

Sea

rch)

WIMP

Nucleus Nucleus

8Detection Principle of Direct Search

Detector

WIMP

Nucleus

0 , ,W DM

WIMP-Nucleus elastic scattering Event rate : ExperimentMeasure this

SUSY models

Limit of R Limit of s

9What is the direct signal for WIMPs ?

1. Recoil energy spectrum as expected at low energy.

2. Annual modulation.

3. Directional asymmetry.

4. A2 dependence (Spin-independent)

Earth velocity (30km/s)

Yearly revolution annual modulation Daily rotation direction change

10

250 kg NaI(Tl) crystals coupled with PMTs.Observed clear annual modulation for 13 years.

PMT+HV divider

DAMA/LIBRA experiment

11Status of WIMP searches

YangYang Pumped Storage Power Plant

YangYang(Y2L) Underground Laboratory

Minimum depth : 700 m / Access to the lab by car (~2km)

(Upper Dam)

(Lower Dam)

(Power Plant)

KIMS (Dark Matter Search)AMoRE (Double Beta Decay Experiment)

Seoul

Y2L

700m

1000m

RENO

13KIMS-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

14Background rates – We are getting there.

• Low threshold down to 1 keV is possible.• Background reduction expected by further purification.

Search for Neutrinoless Double Beta Decays

Ettore Majorana (1906 – 1938 ?)

16Neutrino mixing & oscillation

16

If neutrinos are massive and mixed, then they oscillate.

12

3

1 ?m

m

0

12

3

m

0

17Neutrino mixing & oscillation

17

2

2 2 2 2 2 2 22 1

( )1 sin 2 sin 1.27 ( ) ,

( )

tP

L kmm eV m m m

E GeV

Survival Probability

PRL100, 221803 (2008)

18

Search for Neutrinoless double beta decay (0nbb)

Observation of 0nbb will prove

0 nbbevent

19

Neutrino mass from 0 nbb experiment

Half-lifves of 0nbb inversely proportional to mass2

Half-lifeMeasured

Neutrino Mass

Moore’s law for 0 ?nbbElliott & Vogel, Ann, Phys. (2002)

76Ge, Gerda (0.3) 2013.9136Xe, EXO (0.26) 2012.7

136Xe, KAMLAND-ZEN (0.19) 2013.2

21Overview of AMoRE-200kg

Scintillating Bolometer : 40Ca100MoO4 + MMC

CaMoO4

Light sensorMMC

MMC phonon sensor

<10-50 mK>

AMoRE-200 is the most massive experiment with enriched isotope having Q value > 3MeV.

216 g<Now, 2013>

<2018>

22

MMC (Metallic Magnetic Calorimeter)

paramagnetic sensor: Au:Er

23

Energy resolution data

CaMoO4(natural) with a phonon sensor only.

<2013 KRISS>

FWHM = 9 keV, Goal = 5 keV

24Crystal Growing Facility

Motivation : difficulty to find a reliable and economical company.Will develop chemical purification and crystallization ourself in-side the center. (4 furnaces)

25

Races for 0nbb

Thank you !

27

Dark

Matter G

roup

New

Detector G

roup

Low

Tem

p. Detector G

roup

Double B

eta Decay G

roup

Nu

clear Astrophysics G

roup

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

Organization of CUP

28

Weakly Interacting Massive Particles (WIMP)

이휘소 , 와인버거 박사의 1977 논문 “Cosmological Lower Bound on Heavy-Neu-trino 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 Matter 가 될수 있다 .M(wimp)>2GeV

29

2 Jun.

Time

Back

gro

und

Level

KIMS-CsI annual modulation data

• 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

0.0008±0.0068 cpd/kg/keV

31Comparison with Direct Search

32PMT noise reduction in background data.

DAMA/LIBRA reported PMT noise reduction by introducing charge ratio parameters. KIMS-NaI obtained the same results as DAMA.

X1X2

X1X2

DAMA, E=2-4 keV KIMS-NaI, E=2-4 keV

PMT noise

Real signals

33

Q|fermion> = |boson>particle super particleR 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.

2 3( 1) j B LR

Supersymmetric particles

AMoRE 10

AMoRE 200

Eff

ecti

ve N

eu

trin

o m

ass (

eV

)

Lightest neutrino mass (eV)

Tow

ard

low

er n

eu

trino m

ass

35

Pulse Shape Discrimination

Muon

Gamma

Alpha

and events show different pulse shapes in phonon signals.

Beta-Alpha

36

Phonon sensor for AMoRE

Gold film

We measure both thermal and athermal

phonons.

Phonon collec-torPatterned gold film

Gold wires(thermal connec-

tion)

MMC

rise-time: ~ 0.5ms

<Heat flow optimization>

216 g CaMoO4