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 2014. 5. 9.

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.

Evidences for Dark Matter Existence

More quantitative evidence : cosmic microwave background

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)

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.

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

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

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)

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

Status of WIMP searches

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)

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

Background 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 ?)

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

Neutrino mixing & oscillation Survival Probability PRL100, 221803 (2008)

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

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

Elliott & Vogel, Ann, Phys. (2002) Moore’s law for 0nbb ? Elliott & Vogel, Ann, Phys. (2002) 76Ge, Gerda (0.3) 2013.9 136Xe, EXO (0.26) 2012.7 136Xe, KAMLAND-ZEN (0.19) 2013.2

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.

MMC (Metallic Magnetic Calorimeter) paramagnetic sensor: Au:Er 1.2.3.4.5 수정 Mass 수정 216g

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

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

Races for 0nbb

Thank you !

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

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

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 0.0008±0.0068 cpd/kg/keV

Comparison with Direct Search

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

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.

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

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

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>