Electron Capture Of Potassium-40 40 Presented by: Matthew Stukel, - PowerPoint PPT Presentation

KDK: Measuring The Direct To Ground State Electron Capture Of Potassium-40 40 Presented by: Matthew Stukel, Queen’s University on behalf of the KDK collaboration For the TAUP 2019 Conference 2019/09/12

KDK Collaboration KDK Collaboration N. Brewer [1] , H. Davis [3] ,P. Di Stefano [2] , A. Fijalkowska [1][5][6] , Z. Gai [1] , C. Goetz [3] , R. Grzywacz [3] ,L. Hariasz [2] ,J. Kostensalo [7] , P. Lechner [8] , Y. Liu [1] , E. Lukosi [3] ,M. Mancuso [9] , D. McKinnon [3] , C. Melcher [3] , J. Ninkovic [8] , F. Petricca [9] , C. Rasco [1] , K. Rykaczewski [1] , D. Stracener [1] , J. Suhonen [7] , M. Wolińska -Cichocka [1][4][6] , Itay Yavin [1] Oak Ridge National Lab (ORNL), Tennessee, USA [2] Queen’s University, Kingston, Ontario [3] University of Tennessee, Knoxville, Tennessee [4] Heavy Ion Laboratory UW, Warsaw, Poland [5] University of Warsaw, Warsaw, Poland [6] Joint Institute for Nuclear Physics and Applications [7] University of Jyvaskyla, Jyvaskyla, Finland [8] MPG Semiconductor Laboratory, Munich, Germany [9] Max Planck Institute for Physics, Munich, Germany Technical and Electronic Support from M. Constable, F. Retiere (TRIUMF), K. Dering (Queen’s University), Paul Davis, University of Alberta

Overview 1.What is KDK? 2.KDK Experiment 3.KDK Status (Calibration/Efficiency)

What is KDK? • Pun for “Potassium Decay” • KDK is an international collaboration dedicated to the measurement of the unique thir ird forbidden electron capture decay of 40 K [5] Di Stefano, P.C.F et. Al. 2017. The KDK (potassium decay) experiment. arXiv preprint arXiv:1711.04004 .

Why 40 K? • Rare example of a uniq ique th thir ird forbid idden electron capture decay • Ne Never been experimentally ly measured • 40 K (0.0117%) can be found in natural potassium which is a contaminant in NaI • 40 K is a background in many dark matter experiments (DAMA, SABRE, COSINE-100,etc..) [1] • Can help with interpretation as a dark matter signal (See extra slide) • Increase accuracy in K-Ar Ar (A (Ar-Ar) dati ting • Important Decay Channels: • 10.55 % to Ar-40* through electron capture, EC* • 0.2 % to Ar-40 through electron capture, EC • β - is the dominant decay channel [1] Pradler, Josef, Balraj Singh, and Itay Yavin. "On an unverified nuclear decay and its role in the DAMA experiment." Physics Letters B 720.4-5 (2013): 399-404.

The different branching ratios of 40 K (EC) LOGFT Value Indirect Experimental Half-Life Value 𝐶𝑆 𝐹𝐷 = 0.2 1 % 𝐶𝑆 𝐹𝐷 = 0.8 8 % [3] Be, M.M., Chiste, V., Dulieu, C., Mougeot, X., Chechev, V., Kondev, F., Nichols, A., Huang, X. [1] Pradler, Josef, Balraj Singh, and Itay Yavin. "On an unverified nuclear decay and its role in the DAMA and Wang, B., 1999. Table of Radionuclides (Comments on evaluations). Monographie BIPM- experiment." Physics Letters B 720.4-5 (2013): 399-404. 5 , 7 . KDK Theoretical Value Recent NNDC Value (2017) 𝐶𝑆 𝐹𝐷 = 0.046(6)% 𝐶𝑆 𝐹𝐷 = 0.064(19)% [2] Endt, P.M., 1990. Energy levels of A= 21 – 44 nuclei (VII). Nuclear Physics A , 521 , pp.1- From private communication with J. Kostensalo 400.

KDK Experiment 𝐶𝑆 𝐹𝐷∗ = κ 𝐶𝑆 𝐹𝐷 • A small, inner detector will trigger on the X-rays from 40 K • The internal detector will be surrounded by an larger detector in order to tag the 1460 keV gammas • This will allow us to separate the events caused by the EC* decay from the direct EC

MTAS - External Detector • The external detector is the Modular Total Absorption Spectrometer (MTAS) from Oak Ridge National Lab (ORNL) • The MTAS detector consists of 19 NaI(Tl) hexagonal shaped detectors (53cm x 20cm) weighing in at ~54 kg each • MTAS can provide ~4 π coverage on tagging the 1460 keV gammas • A high efficiency is needed to avoid false positives from the EC* channel and other background sources [4] Karny , M., Rykaczewski, K.P., Fijałkowska, A., Rasco, B.C., Wolińska -Cichocka, M., Grzywacz, R.K., Goetz, K.C., Miller, D. and Zganjar, E.F., 2016. Modular total absorption spectrometer. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment , 836 , pp.83-90.

SDD - Internal Detector

SDD - Internal Detector Chamber

40 K Source Development • ELECTRON BEAM DEPOSITION • The electron beam is created by heating up a tungsten filament • The released electrons are focused towards the tantalum crucible where 3.0 mg of enriched (16% 40 K) KCl is placed • The heat causes the KCl to evaporate and deposit on the graphite disk placed above • Testing thickness of the source was 11 μ m, while actual source used is 5 μ m

KDK Experimental Setup

SDD Energy Spectrum Sample Silicon Escape Peak β + and other backgrounds Auger Electrons X-ray Peaks

SDD Energy Calibration https://indico.cern.ch/event/606690/contributions/2591588/att achments/1497885/2333083/DiStefano_KDK_TAUP_2017.pdf

Data Analysis: 54 Mn • Tagging efficiency = When the SDD is triggered what is the probability of MTAS detecting the associated gamma • Need to know efficiency to ~0.5% in order to make desired 40 K measurement • 54 Mn source used to find our gamma tagging efficiency at 835 keV • Ideal due to the non-existent EC to ground state

Data Analysis: 54 Mn Efficiency Preliminary • Efficiency is calculated by comparing the number of expected coincident and anti-coincident 54 Mn x-rays against the measured ones Preliminary • At a 1 μs coincidence window the efficiency was measured to be 97.72 +/- 0.01 % @ 835 keV • 55 Fe contamination due to source production, visible at the 6.4 keV K β peak

40 K Measurement (Blinded) 40 K visible in MTAS/SDD setup!

40 K Comparison with Simulations

Extra Physics • 88 Y has a third forbidden decay as well. Has never been experimentally measured (barely even theoretically predicted) • Use of the KSr 2 I 5 scintillator as inner detector (See backup slide) • 110m Ag: For reactor neutron flux measurements

Summary • KDK is an experiment dedicated to the measurement of a rare decay of 40 K • Uses a large outer detector MTAS and a small inner detector, SDD • 33 days of data has been taken with a custom 40 K source • Data analysis is ongoing with results expected to be published soon!!!

References 1) Pradler, Josef, Balraj Singh, and Itay Yavin. "On an unverified nuclear decay and its role in the DAMA experiment." Physics Letters B 720.4-5 (2013): 399-404. 2) Endt, P.M., 1990. Energy levels of A= 21 – 44 nuclei (VII). Nuclear Physics A , 521 , pp.1-400. 3) Be, M.M., Chiste, V., Dulieu, C., Mougeot, X., Chechev, V., Kondev, F., Nichols, A., Huang, X. and Wang, B., 1999. Table of Radionuclides (Comments on evaluations). Monographie BIPM-5 , 7 . 4) Karny , M., Rykaczewski, K.P., Fijałkowska, A., Rasco, B.C., Wolińska -Cichocka, M., Grzywacz, R.K., Goetz, K.C., Miller, D. and Zganjar, E.F., 2016. Modular total absorption spectrometer. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment , 836 , pp.83-90. 5) Di Stefano, P.C.F., Brewer, N., Fijałkowska, A., Gai, Z., Goetz, K.C., Grzywacz, R., Hamm, D., Lechner, P., Liu, Y., Lukosi, E. and Mancuso, M., 2017. The KDK (potassium decay) experiment. arXiv preprint arXiv:1711.04004 . 6) Stand, L., Zhuravleva, M., Lindsey, A. and Melcher, C.L., 2015. Growth and characterization of potassium strontium iodide: A new high light yield scintillator with 2.4% energy resolution. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment , 780 , pp.40-44.

Extra Slides

40 K Effects On Annual Modulation Experiments 𝑆 𝑢 = 𝑆 𝑝 + 𝑇 𝑛 (𝑢) 𝑆 𝑢 = 𝐶 𝑝 + 𝑇 𝑝 + 𝑇 𝑛 (𝑢) 𝑡 𝑛 = 𝑇 𝑛 𝑇 𝑝 𝑇 𝑛 𝑡 𝑛 = 𝑆 𝑝 − 𝐶 𝑝 𝑇 𝑛 𝑡 𝑛 = 𝑆 𝑝 − 𝐶 𝑔𝑚𝑏𝑢 − 𝐶 𝑙40 • The uncertainty on BR EC could have an effect on the interpretation of the DAMA signal as a dark matter claim • A high branching ratio would imply a larger B o , meaning less room for S o and thus a higher allowed modulation fraction. (S m /S o ) • This could rule out potential dark matter models that explain an annual modulation signal

APD vs. SDD

MTAS Background Spectrum 40 K: 1460 keV 218 Bi: 1760 keV 208 Tl: 2614 keV 127 I and 23 Na neutron capture peak • Background Spectrum for the MTAS detector • Run Length: 16.7 hrs • The background rate of events in the 1460 keV full collection peak (100 to 4000 keV) ~2400 events/s

Electron Stopping Distance in Silicon • Grey: Dead Layer, Orange: SiO2 Dead Layer, Red: Neutral p+layer (Dead Layer Region), Pink: Depleted n-layer,

X-Ray Transmission probability in SDD • Transmission probability of different energy x-rays • Transmission probability = Chance it will make it to that specific distance in silicon

Unique Third Forbidden Decay l Δ J Δ P Super Allowed 0 0 No Allowed 0 0, 1 No First Forbidden 1 0,1,2 Yes Second Forbidden 2 1,2,3 No Third Forbidden 3 2,3,4 Yes Fourth Forbidden 4 3,4,5 No • Unique transitions are Gamow-Teller transitions where L~ and S~ are aligned.