Technische Universität München Inorganic Scintillators for Rare Event Searches M. v. Sivers, JAPS

Technische Universität München Rare Event Searches with Scintillators ExperimentScintillatorPhysicsTechniqueStatusSite CRESST-IICaWO 4 Dark MatterBolometerRunningLNGS, Italy DAMA/LIBRANaIDark MatterStandardRunningLNGS, Italy KIMSCsI, NaIDark MatterStandardRunningY2L, Korea TEXONOCsINeutrino physicsStandardRunningKSNL, Taiwan CANDLESCaF 2 0ν2βStandardR&DKamioka, Japan DM-IceNaIDark MatterStandardR&DSouth Pole ANAISNaIDark MatterStandardR&DLSC, Spain KAMLAND-PicoNaIDark MatterStandardR&DKamioka, Japan SABRENaIDark MatterStandardR&DLNGS, Italy/SNOLab, Canada (?) LUCIFERZnSe0ν2βBolometerR&DLNGS, Italy (?) LUMINEUZnMoO 4 0ν2βBolometerR&DLSM, France (?) AMORECaMoO 4 0ν2β, Dark Matter BolometerR&DY2L, Korea M. v. Sivers, JAPS

Technische Universität München Standard Scintillation Detectors vs. Bolometers Standard scintillation detector –Crystal at RT, scintillation light detected by PMT –Particle identification by pulseshape possible Scintillating bolometer –Crystal at mK temperature equipped with thermal sensor (phonon channel) –Scintillation light detected by e.g. Si/Ge waver with thermal sensor (light channel) –Particle identification by light/phonon ratio M. v. Sivers, JAPS Crystal PMT e - -recoils O-recoils

Technische Universität München CaWO 4 Crystals In house production at TUM since 2011  Very good radiopurity was achieved: total α-activity (1-3mBq/kg) Light Yield: 40% of NaI(Tl) at RT, 1.7x increase at low temperatures Multi-material target for DM –W (A=184): Good sensitivity for coherent scattering (σ coh ~A 2 ) –Ca, O: Sensitivity to light WIMPs – 183 W (14%): some sensitivity to spin-dependent scattering M. v. Sivers, JAPS IsotopeNatural abundance Decay mode Q-value 48 Ca0.18%2β keV 46 Ca0.004%2β - 988keV 40 Ca96.9%2EC194keV 180 W0.13%2EC144keV 186 W28.4%2β - 490keV

Technische Universität München CRESST-II Dark Matter search with CaWO 4 scintillating bolometers  Discrimination between electron and nuclear recoils by phonon-light technique Observation of 67 candidate events in 730kg days of data (2011)  Maximum Likelihood analysis favored signal over background-only hypothesis with significance >4σ  But large contribution from background demands further clarification M. v. Sivers, JAPS Eur. Phys J. C,72:1971 (2012)

Technische Universität München CRESST-II New run started July 2013  Detector mass doubled  Improved background situation due to cleaner materials and new detector designs Analysis for double beta processes and low-threshold Dark Matter analysis ongoing M. v. Sivers, JAPS

Technische Universität München NaI(Tl) Crystals Most commonly used scintillator  established technique High Light Yield (≈45,000ph/MeV) 23 Na (100%): Sensitivity for light WIMPs and spin-dependent interactions 127 I (100%): Good sensitivity for coherent scattering and spin-dependent interactions Main background for Dark Matter search: 3keV x-ray from EC decay of 40 K M. v. Sivers, JAPS

Technische Universität München DAMA/LIBRA Dark Matter search with 250kg of NaI(Tl) –2keV threshold ( phe/keV), background rate 1cpd/keV/kg (13ppb of nat K) –Positive signal for annual modulation with 8.9σ measured over 13 annual cycles –Fit to rate of single hits between 2-6keV with Acos[ω(t-t 0 )] gives A=(0.0116±0.0013)cpd/kg/keV, ω=(0.999±0.002)yr, t 0 =(146±7)d (t 0 =152.5d expected for DM) –No modulation in multiple hits, no modulation above 6keV –WIMP parameter space excluded by several other experiments But no model-independent check of signal with same target material up to now M. v. Sivers, JAPS DAMA NAIAD Eur. Phys. J. C, 67:39-49 (2010) Phys. Lett. B 616:17-24 (2005)

Technische Universität München DM-Ice 250kg of NaI(Tl) deployed in IceCube detector –Goal: Check DAMA claim on southern hemisphere –17kg of NAIAD crystals as prototype running since 2011 Current background 7x higher then DAMA (650ppb nat K)  R&D for crystal growth ongoing, pushing threshold below 4keV M. v. Sivers, JAPS Astropart. Phys. 35 (2012)

Technische Universität München ANAIS Dark Matter search with 250kg of NaI(Tl) –25kg prototype running since Dec  40ppb of nat K (3x higher than DAMA)  High light collection 12-16phe/keV without lightguides (2x higher than DAMA)  R&D on crystal growth ongoing (goal <20ppb nat K) M. v. Sivers, JAPS arXiv:

Technische Universität München SABRE Dark Matter search with 100kg of NaI(Tl) crystals in liquid scintillator (LAB) veto –Purchased 8kg of NaI powder with 12ppb/3.5ppb nat K –First step: measure 40 K concentration in crystals with liquid scintillator coincidence –Second step: Move chamber to LNGS or SNOLab for DM run –Expected background rate 0.39cpd/kg/keV (2.5x lower than DAMA) M. v. Sivers, JAPS See Talk by E. Shields at TAUP2013

Technische Universität München CsI(Tl) Crystals High Light Yield: 60,000ph/MeV 127 I, 133 Cs: Good sensitivity for coherent scattering and spin-dependent interactions Pulseshape discrimination possible M. v. Sivers, JAPS

Technische Universität München KIMS Dark Matter search with 100kg of CsI(Tl) –Light yield 5phe/keV, background rate 2-4cpd/kg/keV –Total exposure 24.5ton days –Excludes DAMA signal as WIMP scattering on iodine Annual modulation analysis with 2.5years (75.5ton days) data –amplitude <0.0122cpd/kg/keV at 90%CL (DAMA signal ± cpd/kg/keV) M. v. Sivers, JAPS PRL 108, (2012)

Technische Universität München CaF 2 Crystals Light Yield: 24,000ph/MeV (CaF 2 (Eu)) 48 Ca (0.18%): 0ν2β candidate with highest Q-value (4.27MeV) –Enrichment difficult (no gaseous Ca compunds): 1g of 48 Ca costs $100k 19 F (100%): Sensitivity to spin-dependent interactions Pulseshape discrimination possible M. v. Sivers, JAPS IsotopeNatural abundance Decay mode Q-value 46 Ca0.004%2β - 988keV 40 Ca96.9%2EC194keV

Technische Universität München CANDLES III Search for 0ν2β with 305kg CaF 2 (pure) in liquid scintillator veto –Best limit on 0ν2β of 48 Ca from predecessor ELEGANT VI (exposure 4.23kg yrs): T 1/2 >1.4e22y (Nucl. Phys. A 730 (2004) 215–223) –R&D on enrichment of 48 Ca: chemical processing with crown ether, Laser separation M. v. Sivers, JAPS See talk by Umehara at TAUP2013

Technische Universität München ZnSe Crystals 82 Se (7.8%): Candidate for 0ν2β (Q-value 2996keV) High radiopurity: 17μBq/kg ( 226 Ra, 232 Th) Light Yield at low temperature: 7.4keV/MeV (CaWO 4 : 20keV/MeV) Pulseshape discrimination possible Inverse quenching factor (LY α /LY γ =4.2) not yet understood M. v. Sivers, JAPS alphas gammas IsotopeNatural abundance Decay mode Q-value 64 Zn49.2%2EC, ECβ keV 70 Zn0.61%2β - 999keV 74 Se0.89%2EC, ECβ keV

Technische Universität München LUCIFER Search for 0ν2β with Zn 82 Se scintillating bolometers –Good energy resolution –Discrimination of alphas with phonon-light technique and PSD Sensitivity goal of =100meV: 10kg of 95% enriched 82 Se, 5 years exposure, <10 -3 counts/kg/keV/y, 5keV resolution Possibility to also search for DM M. v. Sivers, JAPS arXiv: Astropart. Phys. 34: (2011)

Technische Universität München ZnMoO 4 Crystals 100 Mo (9.6%): Candidate for 0ν2β (Q-value 3034keV) Low Light Yield at low temperatures: 1keV/MeV High radiopurity: <32μBq/kg ( 226 Ra, 228 Th) M. v. Sivers, JAPS IsotopeNatural abundance Decay mode Q-value 64 Zn49.2%2EC, ECβ keV 70 Zn0.61%2β - 999keV 92 Mo14.8%2EC, ECβ keV

Technische Universität München LUMINEU Search for 0ν2β with Zn 100 MoO 4 scintillating bolometers –Good energy resolution –Discrimination of alphas with phonon-light technique and PSD (discr. power 20σ!) Sensitivity goal of =100meV: 30kg of 90% enriched detectors, 5 years exposure, ≈1.5*10 -3 counts/kg/keV/y, 5keV resolution Main background from pileup of 2ν2β: development of faster detectors Collaboration with TUM to grow high purity ZnMoO 4 crystals M. v. Sivers, JAPS arXiv:

Technische Universität München CaMoO 4 Crystals Highest Light Yield among molybdates: 30,000ph/MeV (at low temp.) For 0ν2β of 100 Mo (Q-value 3034keV) 2ν2β of 48 Ca (Q-value 4270keV) serves as background High radiopurity: ≈80μBq/kg ( 226 Ra, 228 Th) Pulseshape discrimination possible M. v. Sivers, JAPS IsotopeNatural abundance Decay mode Q-value 46 Ca0.004%2β - 988keV 40 Ca96.9%2EC194keV 92 Mo14.8%2EC, ECβ keV

Technische Universität München AMORE Search for 0ν2β with 40 Ca 100 MoO 4 scintillating bolometers (depleted in 48 Ca) –Discrimination of alphas with phonon-light technique and PSD –Good energy resolution Sensitivity goal =20-60meV: 250kg yrs exposure Possibility to also search for Dark Matter (AMORE-DARK) M. v. Sivers, JAPS See talk by Y. Kim at RPScint13

Technische Universität München Summary Inorganic scintillators –Key properties for rare event searches: Radiopurity, Light Yield –Advantages: Wide choice of materials Multimaterial approach: –Simultaneous sensitivity to spin-dependent and coherent interactions/light and heavy WIMPs –Possibility to study many rare decays in one experiment (e.g. 2β, 2EC, ECβ +, …) –Disadvantages: Crystal growth is extensive, especially for ton-scale experiments No purification possible after crystal growth Scintillating bolometers –Very good energy resolution –Active background discrimination with phonon-light technique –Promising for next generation 0ν2β experiments (zero background seems feasible) M. v. Sivers, JAPS