Walter C. Pettus University of Wisconsin Madison. Weak Interactions Discussion Group Yale Physics 21 Oct 2013

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1 Walter C. Pettus University of Wisconsin Madison Weak Interactions Discussion Group Yale Physics 21 Oct 2013

2 Dark Matter and DM- ICE Cosmogenic Activation in DM- ICE O( kev ee ) Calibration Pulse Shape Discrimination O(>2500 kev ee ) Calibration Noise Discrimination O(<20 kev ee ) Calibration WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 1

3 Planck collaboration, arxiv: (2013) 26.8% of Universe is dark matter Cosmic Microwave Background Baryon Acoustic Oscillations Distance Measurements (H 0 ) Type Ia Supernovae Gravitational Lensing Cluster Measurements Lyman Alpha Forest Large Scale Structure Galactic Rotation Curves WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 2

4 Best Exclusion Limits DAMA/NaI 100 kg (0.29 ton yr) DAMA/LIBRA 250 kg (0.87 ton yr) Nagging Positive Signals 2-6 kev Agnese et al. arxiv: (2013) Residuals (cpd/kg/kev) DAMA/NaI 100 kg (0.29 ton yr) DAMA/LIBRA 250 kg (0.87 ton yr) Bernabei et al. Int J Mod Phys A (2013) Time (day) Fig. 1. Experimental model-independent residual rate of the single-hit scintillation events, measured by DAMA/NaI over seven and by DAMA/LIBRA over six annual cyclesinthe(2 4),(2 5), and (2 6) kev energy intervals as a function of the time. 116, 171, 175, 176 The zero of the time scale is January 1 st of the first year of data taking. The experimental points present the errors as vertical bars and the associated time bin width as horizontal bars. The superimposed curves are A cos ω(t t 0)withperiodT = 2π ω =1yr,phaset0 =152.5 day(june2nd )andmodulation amplitude, A, equaltothecentralvalueobtainedbybestfitoverthewholedata: cumulative exposure is 1.17 ton yr. The dashed vertical lines correspond to the maximum expected for the DM signal (June 2 nd ), while the dotted vertical lines correspond to the minimum. SeeRefs.175, WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 3

5 Instruments and Methods in Physics Research A 592 (2008) LNGS (DAMA) Search for annual modulation with NaI(Tl) crystals in the Southern Hemisphere South Pole (DM- Ice) x2 DAMA/LIBRA 5x5 array ~250 kg WIDG, 21 Oct 2013 DM- Ice (concept) 7 crystal array ~125 kg/module ~250 kg total Walter C. Pettus, UW Madison procedures involving detectors, photomultipliers (PMTs), etc. have been carried out in HP (High Purity) oor, etc.) after removal of the DAMA/NaI electronics (top left); dismounting the DAMA/NaI detectors in HP etector in HP Nitrogen atmosphere (bottom left); installing the DAMA/LIBRA detectors in HP Nitrogen by the DAMA/LIBRA detectors in HP Nitrogen atmosphere (bottom right). 4

6 2 detectors 8.47 kg each 2457 m depth 2200 m.w.e. Deployed Dec 2010 Stable running since June 2011 WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 5

7 counts / day / kev / kg Pb Pb 214 Pb 208 Tl Bi counts / day / kev / kg I 210 Pb 40 K 210 Pb Energy (kev) Co 40 K 214 Bi 214Bi 208 Tl Energy (kev) WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 6

8 Cosmic ray shower components can activate detector components Muon capture μ + A(Z,N) ν μ +A(Z 1,N+1) Hadron capture n + A(Z,N) A(Z,N+1) p + A(Z,N) A(Z+1,N) Spallation n + A(Z,N) n + A 1 (Z 1,N 1 ) + A 2 (Z 2,N 2 ) WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 7

9 Altitude Dependence: Latitude Dependence: Ziegler. IBM J R&D (1998) Beringer et al. (PDG) Phys Rev D (2012) Cosmic ray rates depend on altitude (atmospheric depth) and geographic coordinates (geomagnetic rigidity) WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 8

10 Before running a dark matter experiment at the South Pole... Sandiviken, SWE DM- ICE17 Component Sources Crystals: Boulby, UK Steel: Sandviken, SWE DM- ICE17 Construction Madison, WI, USA Polar Program Waypoints Christchurch, NZ McMurdo Station South Pole Station Christchurch, NZ McMurdo Station Madison, WI Boulby, UK South Pole Station WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 9

11 Commercial flights at ~35,000+ ft Location Relative Neutron Rate (to sea level) Madison, WI 1.26 South Pole 9.7 Commercial Flight 130 Madison, WI Sandiviken, SWE Boulby, UK Polar program flights Storage at 9,301 ft South Pole Station Christchurch, NZ McMurdo Station Low geomagnetic rigidity WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 10

12 Activity of cosmogenic isotopes simulated by: ACTIVIA code for NaI crystals Literature values for Steel (and Copper) Crystal Steel Isotope Half- Life Isotope Half- Life 3 H 12.3 yr 22 Na 2.6 yr 109 Cd 461 d 113 Sn 115 d 121 Te 19.2 d 7 Be 53.2 d 46 Sc 83.8 d 48 V 16.0 d 51 Cr 27.7 d 52 Mn 5.59 d 121m Te 123m Te 125m Te 127m Te 164 d 119 d 57.4 d 106 d 54 Mn 312 d 56 Co 77 d 56 Ni 70.9 d 58 Co 6.08 d 125 I 59.4 d 126 I 12.9 d 127 Xe 36.3 d WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 11

13 Breakdown of crystal activation by travel stage: Christchurch (25 days) South Pole (15 days) Wisconsin (60 days) Flight: MCM NPX (3 hrs) Flight: CHC MCM (5 hrs) Flight: MSN CHC (16 hrs) WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 12

14 Long- lived cosmogenic isotopes from crystal and pressure vessel are expected to persist into data taking 1 st Data Month: Simulated Spectrum Crystal Steel 3 H 7 Be 22 Na 46 Sc 109 Cd 48 V counts/kg/kev/day 113 Sn 51 Cr 121m Te 123m Te 125m Te 127m Te 52 Mn 54 Mn 56 Co 56 Ni 125 I 58 Co 127 Xe Energy (kev) WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 13

15 * (6.5 months after deployment, first month of data run) NaI Crystal Still expect clear peaks from multiple isotopes Steel Pressure Vessel 54 Mn is only significant isotope counts/kg/kev/day NaI Crystal Cosmogenics: All in Crystal 113 Sn in Crystal 121m Te in Crystal 123m Te in Crystal 125m Te in Crystal 127m Te in Crystal 125 I in Crystal counts/kg/kev/day Pressure Vessel Cosmogenics: Energy (kev) Energy (kev) WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 14

16 125 I (t 1/2 = 59.4 days) is good candidate for search in early data months counts (arb) Geant4 125 I Energy Deposited counts / day / kev / kg July 2011 June 2013 Residual 125 I X- rays 125 I Full Energy WIDG, 21 Oct 2013 Energy (kev) Energy (kev) Walter C. Pettus, UW Madison 15

17 λ = ± month - 1 t 1/2 = ± 2.66 days (59.4 days) Deploy activity: 1151 ± 118 cpd/kg Integrated Peak Area (counts/kg/day) 125 I Peak Decay Month (since July 2011) WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 16

18 γ- line expected from 54 Mn E γ = 835 kev t 1/2 = days counts / day / kev / kg July 2011 June 2013 Residual Fit Expectation -1 Energy (kev) ± Sigma (kev) 36.9 ± Energy (kev) Deploy Rate (decays/day) 51,700 ± 6, ,800 WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 17

19 Both ANAIS and DAMA observe 125 I peak ANAIS also looking into presence of other NaI cosmogenics (esp. Te states) DAMA/LIBRA Bernabei et al. NIMA (2008) a) Deployment b) Months later ANAIS- 25 Martinez. LNGS Seminar (2013) 8- week residual WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 18

20 Time on surface at South Pole can be most damaging stage for cosmogenics: Christchurch Wisconsin Flight: MCM NPX Flight: CHC MCM South Pole Flight: MSN CHC South Pole is topographically flat and station buildings provide minimal overburden WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 19

21 40-50 ft firn overburden ~ 10 m.w.e. ~ 30% of surface muon rate WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 20

22 Muon spectra comparison of South Pole sites with Christchurch and Madison data Count Rate (/MeV/min) MCA1 Compiled Average Data South Pole - Surface South Pole - ICL South Pole - Tunnel Christchurch, NZ Madison, WI, USA Energy (MeV) WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 21

23 Location Elevation (ft) Relative Intensity* South Pole - Surface South Pole ICL South Pole Tunnel Christchurch, NZ Madison, WI, USA South Pole Tunnels (15 days) Christchurch (25 days) Wisconsin (60 days) Flight: MCM NPX (3 hrs) Flight: CHC MCM (5 hrs) *Relative to Christchurch approximately sea level Flight: MSN CHC (16 hrs) WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 22

24 Growing crystals with Alpha Spectra Inc. (Grand Junction, CO) for next phase 4,600 ft above sea level What cosmogenic products can we measure in these crystals? WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 23

25 330 ft overburden

26 Test Crystal in Castle Castle (closed) with DAQ WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 25

27 Cosmogenics allow energy calibration in kev range Testing underway to investigate cosmogenic effect on next- phase DM- ICE counts / day / kev / kg Pb Pb 214 Pb 54 Mn 208 Tl Bi counts / day / kev / kg I 210 Pb 40 K 210 Pb Energy (kev) 60 Co 40 K 214 Bi 214Bi 125 I 208 Tl Energy (kev) WIDG, 21 Oct 2013 Walter C. Pettus, UW Madison 26