Down-to-earth searches for cosmological dark matter

Transcription

1 Down-to-earth searches for cosmological dark matter Carter Hall, University of Maryland October 19, 2016

2 Astrophysical evidence for dark matter Galaxy cluster collisions Rotation curves Ω

3 380,000 years after the big bang 13.9 billion years Today Credit: Andrey Kravtsov, KICP, U. Chicago 1970 s s: Cold dark matter is needed to seed the formation of galaxy clusters 3

4 Temperature and density fluctuations are 1 part in The cosmic microwave background anisotropy imaged Planck (2014). 4

5 CMB multipole expansion - measured by Planck (2014) ~ 1 Prominent 3 rd peak indicates presence of matter which did not rebound. ~ 1/2 ~ 1/3 5

6 Neutrinos? not heavy enough generalize Weakly Interacting Massive Particle

7 The thermal hypothesis: Was the dark matter an interacting component in the very early universe? Early universe plasma Dark matter annihilation Dark matter Normal matter? Age of universe ~ 1 nanosecond; Temperature ~ 100 GeV Dark matter Dark matter creation Normal matter

8 The thermal hypothesis: Was the dark matter an interacting component in the very early universe? Small annihilation cross section Typical weak nuclear force cross sections Correct dark matter abundance Large annihilation cross section J. Feng, Annu. Rev. Astron. Astrophys :

9 The Milky Way s dark matter halo Typical orbital vel. = 230 km/sec ~ 0.1% speed of light Density: ~ 300 m proton / liter WIMPs (~100 GeV): 3 per liter debroglie wavelength: WIMPs: larger than a nucleus. Coherent scalar scattering on ordinary nuclear matter, σ ~ A 2 Production: WIMPs: thermal

10 Dark matter annihilation Dark matter Normal matter? Dark matter Normal matter Dark matter creation

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12 HAWC projected five-year sensitivity (start 2015)

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15 Direct detection Dark matter Normal matter? Dark matter Normal matter

16 Direct Detection WIMP nuclear recoil signal γ,β electron recoil background

17 The parameter space of direct detection & XENONNT

18 Nuclear recoil energy spectra A 2 dependence From: arxiv:

19 Calibration of LUX: Beta spectrum of Carbon-14 Carbon-14 beta decay Detector threshold = 1.3 kev Xenon-131 Gamma line (164 kev) 1-8 kev: x-ray region

20 Detection modes for ionizing radiation Nuclear recoils vs. electron recoils "Division of energy "Timing "Stopping power Two-phase noble liquids (PandaX, XENON, LUX) Ionization Target WIMP Cryogenic semiconductors (CDMS) Phonons/heat 100% energy slowest cryogenics Single-Phase noble liquids (XMASS, DEAP/CLEAN) Light WIMP scintillating bolometers (CRESST) 20

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22 Typical Event in LUX S1 S2 22

23 Strong background rejection from kinematics ~ kev deposition must cross full volume without interacting again ~ MeV γ forward scattering 23

24 Simulation of self-shielding in liquid xenon Volume cut rejects most gamma backgrounds. 24

25 Particle ID: recoil discrimination in LUX Charge/Light Electron recoils (background) Charge/Light Nuclear recoils (signal) Charge/Light Difference Electron recoil rejection factor: Light 25

26 LUX assembly kg of liquid xenon 26

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28 Sanford Underground Research Facility Davis Cavern 1480 m (4200 mwe) LUX Water Tank South Dakota USA 28

29 Davis SURF, March

30 Davis Campus dedication, May 30, 2012 Davis Campus water tank, home of LUX Ana Davis, widow of Ray Davis 30

31 On top of the water shield, Sept

32 LUX installed underground, Sept

33 LUX recoil bands and energy scales electron recoil band less charge recombination nuclear recoil band more charge recombination 33

34 LUX WIMP search data (2013) 1.3 kev ee events observed 85.3 days kg = 10,090 kgdays Charge Light log 10 (S2 b /S1) x,y,z corrected kevnr S1 x,y,z corrected (phe) Light 2013 initial results (Run 3): Phys.Rev.Lett. 112 (2014) re-analysis of Run 3: Phys.Rev.Lett. 116 (2016)

35 October 30, 2013

36 Calibration: external gamma sources ( 137 Cs) Calibration source guide tubes Self-shielding makes external gamma sources mostly ineffectual

37 Tritium: an ideal electron-recoil band calibration source Tritium Beta Spectrum (Q=18.6 kev, T1/2=12.3 years) 2 Counts/keV/day/ atoms WIMP search range H H C T H Electron Kinetic Energy [kev] 37

38 Injection and removal of tritium from LUX, August Fiducial S1 count <150 [Phe]. rate Fiducial for S1 Volume < 150 PE Rate τ 1 =6.0 ±0.5Hours τ 2 =6.4 ±0.1 Hours August 8, 2013 Rate (Hz) 10 2 Success /21/ Time (hours) 38

39 Tritium event locations in LUX August 2013 y (cm) x (cm) drift time (µs) radius squared (cm 2 ) 39

40 Charge vs Light from tritium in LUX at 170 V/cm 10/21/16 178,000 fiducial tritium events 40

41 Tritium combined-energy spectrum 178,000 fiducial tritium events 41

42 Light yield of liquid xenon LUX tritium (100 & 180 V/cm)

43 Nuclear-recoil calibration w/mono-energetic neutrons D + D n + 3 He E n = 2.45 MeV

44 Nuclear-recoil calibration of LUX Neutron scattering with a neutron generator

45 LUX final WIMP search results Run 3 & 4 combined, LUX Run 3 & 4 (2016): arxiv:

46 LUX -> LZ (2020) Scale up LUX fiducial mass by x40 LZ: Total Xe - 10 Ton Ac5ve Xe 7 Ton Fiducial Xe 5.6 Ton LUX LUX 46

47 The LZ Experiment coming in 2020 Xe TPC existing LUX water shield 50 kv high voltage Gd-doped liquid scintillator outer detector 47

48 LZ Sensitivity (5.6 Tonnes, 1000 live days) cm 2 48

49 History of WIMP 50 GeV Ge, NaI no discrimination Ge, w/discrim. ZEPLIN XENON100 LXe, w/discrim. LUX (2013) LUX & PandaX-II (2016) LZ XENON 1T

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51 Uranium-238 decay chain start Thorium-232 decay chain start gamma sources end end 51

52 Ordinary radioactive decay here on earth K-40 Bi-214 (U-238) Tl-208 (Th-232) WIMP scattering ββ0ν Q values: Ge-76 Xe-136 Te

53 Two problems from particle physics 1) Why is the weak scale so light? è New weak physics? è WIMPs 2) Why no CP violation in QCD? è Peccei-Quinn symmetry?è Axions

54 Electron-recoil and nuclear-recoil calibration data 54

55 Is LUX a success?

56 July 22, 2016