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

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 -

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 !

Composition of our Universe Mostly Dark …

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 10-28 kg/cm3

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

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

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

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

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 = 54.3/66 8.2  C.L. Fit :Acos[w(t-t0)]

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

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

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

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

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

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

Yangyang Underground Laboratory(Y2L)

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)

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

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

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

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

WIMP search limit with 4 crystals PRL 99, 091301 (2007) Nuclear recoil of 127I of DAMA signal region is ruled out unambiguiously Most stringent limit on SD(pure proton) interactions

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. 2009 ~ Aug. 2010 Total exposure: 32793 kg days

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 59.54 gamma Relative intensity..... E(keV)

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

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

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

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)

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

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

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.

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

KIMS WIMP search Spin Independent Spin Dependent preliminary

Plan on Annual Modulation Stuudy Taking data for more than 18 months  2 year data by this summer Sep. 2009 ~ Feb. 2011 ~ 3 counts/day/kg/keV

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

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.

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

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

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; 450-650ns-> 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

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

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)

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

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

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

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

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

Dark matter sensitivity of CaMoO4 cryogenic experiment Bottino et al Trotta et al Ellis et al CaMoO4 CDMS 2008 SuperCDMS 25kg XENON10 2007 XENON100 6000 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

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

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

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

Thank you

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 0808.3607 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

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