Do WIMPs Rule? The LUX & LZ Experiments and the Search for Cosmic Dark Matter!" Dan Akerib! SLAC National Accelerator Laboratory Kavli Insitute for Particle Astrophysics & Cosmology
Standard cosmology: An inventory of the universe SDSS-III / BOSS from Perlmutter, Phys. Today (units of critical density) supernovae Energy density Baryon acoustic oscillations Matter density 3 Kelvin cosmic microwave background WMAP WMAP Tytler & Burles
WIMP Hypothesis Early Universe as Particle Factory Not enough protons and neutrons produced in the Big Bang Convert energy to mass E=mc 2 quark WIMP distance anti-quark anti-wimp A new type of particle: WIMPs = weakly interacting massive particles Massive: source of gravity Weakly-interacting: not star forming time
cross section annihilation rate
cross section annihilation rate
WIMP freezeout WIMP pairs produced in equilibrium Annihilation stops when number density falls too low H > Γ A ~ n χ σ A v Production = Annihilation (T m χ ) Production suppressed (T<m χ ) Freeze out annihilation rate slower than Hubble expansion ( freeze out ) mean free time > age For Ω χ 1 M 10-1000 GeV σ A electroweak SUSY/LSP? Comoving Number Density ~exp(-m/t) Jungman, Greist, Kamionkowski 1996 1 10 100 1000 m χ / T (time )
Dark Matter in Galactic Halos data with dark halo if only stars and gas Vera Rubin and Kent Ford, 1978
Scattering experiment WIMP 10 16 WIMPs/year density, speed dark matter halo 10-16 light years 1 light year Cross section: WIMP scatters once in a light year of lead detector Rate ~ few events / year
WIMP search - c.1988: converted neutrino detector Germanium ionization detector at the Oroville Dam, CA searching for double beta decay - progenitor to Majorana Event rate ruled out heavy neutrinos as DM Recoil energy transfer to nucleus from Jungman et al. (D.O. Caldwell et al.)
WIMP search - c.1988: converted neutrino detector Germanium ionization detector at the Oroville Dam, CA searching for double beta decay - progenitor to Majorana Event rate log cross section (arb. units) 070802080001 http://dmtools.brown.edu/ Gaitskell,Mandic,Filippini 0 1 10 2 10 3 WIMP Mass [GeV] Recoil energy transfer to nucleus from Jungman et al. (D.O. Caldwell et al.)
Energy deposition WIMP 10% energy Ionization Phonons/heat 100% energy slowest cryogenics Light 1% energy fastest no surface effects
An active field with many approaches! WIMP CoGent (HPGe) DMTPC (gas dir.) DRIFT (gas dir.) 2-phase nobles: ZEPLIN, XENON, WARP, LUX/LZ, ArDM, Darkside 10% energy Ionization Semiconducting calorimeters: CDMS, Edelweiss Superheated liquids: Picasso, Simple, Coupp, PICO Phonons/heat 100% energy slowest Inorganic scintillators: DAMA/LIBRA, KIMS Single-phase liquid nobles: DEAP, MiniCLEAN, XMASS Light 1% energy fastest CRESST II low radioactivity background immunity large mass / stable operation shielded low energy threshold
Water, 2.6 MeV gammas Shielding Gamma Rays Water 1 m water shielding Liquid Xe, 2.6 MeV gammas Liquid Xenon 1 m liquid Xe
The Large Underground Xenon Detector 250 kg active LXe @ 170 K S1, S2 event energy S2 event xy location S1-S2 timing z location S2/S1 recoil type z y x
Inside the LUX/LZ water tank Sanford Underground Research Facility 4850-foot deep Davis Cavern Homestake Gold Mine Lead, SD The LUX Experiment photo credits: Matt Kapust, SURF
Former Homestake Gold Mine Sanford Underground Research Facility
Backgrounds: neutrons cosmic ray muons Gammas in Water muons down by 10,000,000x neutron scatter nuclear disintegration neutron moderated by water shield photo credit: Matt Kapust, Sanford Lab
1964 Nov 2011 2009
Internal dangers: radioactive 85 Kr 10-y T 1/2 beta decay Can t self-shield Noble gas: non-reactive ~130 ppb in purchased Xe LUX background floor from 122 PMTs ~ 20 ppt Kr/Xe ν e - 85 Kr 85 Rb + e - + ν e - Kr Xe Chromatography He gamma ray
Gas charcoal chromatography Kr removal Kr Xe He
400 kg Xe at Case: 130 ppb to 4 ppt thermosyphon dewar traps thermosyphon lines (3) charcoal column condenser gas panel gas control panel Xe recovery pumps sampling RGA graduate student Chang Lee feed & recovery bottles arxi C. Hall, UMD: Assay with ppt sensitivity
50 kg / week processed for LUX Xe partial pressure Xe feed (mass) (arb units) 45 kg 4 days
Raw signals in LUX Depth from timing difference z y x Lateral location from top PMT Array
Signal production in liquid Xe e - E ~ kev Xe Xe + Ion Xe2 + Ionized molecule e - e - e - S2 Recombination Xe Xe Heat Xe Xe* Excitation Xe2* VUV photon, 175nm S1 Electron Recoils
Signal production in liquid Xe Xe E ~ kev Xe Xe + Ion Xe2 + Ionized molecule e - e - e - S2 Recombination Xe Xe Heat Xe Xe* Excitation Xe2* VUV photon, 175nm S1 Nuclear Recoils
Understanding light and charge Electric Field Electron recoils Nuclear recoils Puzzling low energy behavior Comprehensive model, only 2 fit parameters (Dahl, PhD thesis, 2009) Robust Monte Carlo framework: NEST (M. Szydagis et al., JINST 6, p10002 (2011))
Background and Signal Distinction Background in situ LUX calibrations More charge, less light Signal τ Internal tritium source (purified away with ~ 7 hours)
WIMP signal Signal region: a quiet place where low-energy singlescatter nuclear recoils away from the walls can emerge from among: external gamma rays into the fiducial volume wall events (206Pb) dissolved backgrounds (Rn-progeny, 85Kr, 127Xe) delayed electrons from previous large S2 s amplitude (phe/10 ns) S1 summed across all channels 0.6 0.5 0.4 0.3 ALPHA POPULATIONS IN XY amplitude (phe/10ns) 1.5 1 0.5 0.2 100 0 0.1 50 0 50 100 150 0 200 PMT channel ALPHA POPULATIONS IN number R 2 0 0.2 0 0.2 0.4 Z time (µs) time (µs) 150 83m Kr injection movie 550 sec 83m Kr injection movie 550 sec
0.6 Event selection S1 summed across all channels S2 summed across all channels 0.5 8 amplitude (phe/10 ns) 0.4 0.3 0.2 0.1 amplitude (phe/10 ns) 6 4 2 amplitude (phe/10ns) 1.5 1 0.5 0 0 0.2 0 0.2 0.4 time (µs) S1 0 179 180 181 182 183 184 time (µs) S1 150 100 50 0 50 100 150 200 time (µs) 0 PMT channel number Requirements for WIMP search candidate events S2 trigger (at least 2 trigger ch. 8 phe within 2 µs) [lower threshold than S1] 2 phe (2-fold coincidence) S1 30 phe [quiet enough to see this in look back ] 200 phe (8 e-) S2 3300 phe [require good xy measurement] total area of other pulses in the event < 100 phe [confusion from previous large S2's]
LUX WIMP Search, 85 live-days, 118 kg calibration 2.6 2.4 1.3 kev ee 1.8 ER Calibration 99.6±0.1% leakage below NR mean, so expect 0.64 +/- 0.16 for 160 events log (S2 /S1) x,y,z corrected 10 b 2.2 2 1.8 1.6 1.4 3.5 4.6 5.9 7.1 1.2 0 3 6 9 12 15 18 21 24 27 30 kevnr 1 0 10 20 30 40 50 S1 x,y,z corrected (phe) gate grid drift time (µs) 50 100 150 200 250 300 wall face wall corner 350 cathode grid 0 100 200 300 400 500 600 radius 2 (cm 2 ) 160 events in ER band / 118 kg fiducial
Extended Likelihood Treatment Observables: x = (S1, log 10 (S2/S1), r, z) Parameter of interest: Nuisance parameters: N s N Compt, N Xe-127, N Rn/Kr-85 Modeled WIMP signal, including resolution and efficiencies 8 GeV /c 2 WIMP 100 GeV /c 2 WIMP 2 TeV /c 2 WIMP
Spin Independent Cross Section Upper Limit WIMP nucleon cross section (cm 2 ) 10 44 10 45 ZEPLIN III Edelweiss II CDMS II Ge XENON100(2011)-100 live days XENON100(2012)-225 live days LUX (2013)-85 live days LUX +/-1σ expected sensitivity 10 1 10 2 m (GeV/c 2 10 3 ) WIMP Phys. Rev. Lett. 112, 091303 (2014)
Spin Independent Cross Section Upper Limit WIMP nucleon cross section (cm 2 ) 10 40 10 41 10 42 10 43 10 44 10 45 10 1 10 2 m WIMP (GeV/c 2 10 3 )
Low Mass WIMPs CDMS II Ge WIMP nucleon cross section (cm 2 ) 10 40 10 41 10 42 10 43 DAMA/LIBRA Favored CoGeNT Favored x CDMS II Si Favored XENON100(2012) 225 live days CRESST Favored 10 44 LUX (2013) -85 live days 5 6 7 8 9 10 12 m WIMP (GeV/c 2 ) w/newest CDMS result
Next for LUX WIMP nucleon cross section (cm 2 ) 10 40 10 41 10 42 10 43 10 44 10 45 10 46 DAMA/LIBRA CoGeNT (2012) CDMS II Si (2013) CRESST II ZEPLIN III XENON100 10 1 10 2 m (GeV/c 2 10 3 ) WIMP CDMS II Ge LUX 85d (2013) Projected LUX 300 day run (2014-15) Updated analysis of 85d - improved reconstruction - lower threshold - wall distribution into PLR? - complete DD calibration - NEST update! 300d run: above + - improved extraction field - 127 Xe decayed away
LZ: LUX + ZEPLIN 20-fold scale-up from LUX Two-component outer detector system 0.75 m thick Gd-loaded LAB scintillator shield (c.f.: Daya Bay) Instrumented Xe skin Effective for neutrons and gammas HV water shield scintillator detector 7 ton LXe TPC fits in Davis Cavern
LZ Reach and Snowmass WIMP nucleon cross section cm 2 10 39 10 40 10 41 10 42 10 43 10 44 7 Be 10 45 Neutrinos 10 46 10 47 10 48 10 49 10 50 SuperCDMS PICO250-C3F8 CDMSlite (2013) SNOLAB NEUTRINO C OHER ENT SCATTERING 8 B Neutrinos (Green&ovals)&Asymmetric&DM&& (Violet&oval)&Magne7c&DM& (Blue&oval)&Extra&dimensions&& (Red&circle)&SUSY&MSSM& &&&&&MSSM:&Pure&Higgsino&& &&&&&MSSM:&A&funnel& &&&&&MSSM:&BinoEstop&coannihila7on& &&&&&MSSM:&BinoEsquark&coannihila7on& & SuperCDMS Soudan Low Threshold XENON 10 S2 (2013) CDMS-II Ge Low Threshold (2011) CoGeNT (2012) CRESST Updated from Snowmass Community Summer Study 2013 CF1: WIMP Dark Matter Detection CDMS Si (2013) DAMA EDELWEISS (2011) DEAP3600 1 10 100 1000 10 4 WIMP Mass GeV c 2 SIMPLE (2012) SuperCDMS Soudan LUX 300-day SuperCDMS SNOLAB NEUTRINO COHERENT SCATTERING Atmospheric and DSNB Neutrinos COUPP (2012) ZEPLIN-III (2012) CDMS II Ge (2009) Xenon100 (2012) LUX (2013) DarkSide 50 PICO250-CF3I Xenon1T DarkSide G2 LZ 10 3 10 4 10 5 10 6 10 7 10 8 10 9 10 10 10 11 10 12 10 13 10 14 WIMP nucleon cross section pb 3 year run, limited primarily by (electron recoil) background of pp solar neutrinos limited by nuclear scatter background? reach to 10-49 cm 2 neutrino floor depends on rejecting pp solar
Lab Activities at SLAC Fundamental measurements Test platform for LZ prototyping and long-term R&D 45 cm 80 cm Purification Tower Test TPC in 100 kg LXe @ 170 K LXe vessels w/200 kv feedthrough ports for LZ system test HV feedthrough (drift field) Removal of trace radioactive 85 Kr thermosyphon w/gas dewar charcoal chromatography high-flow pneumatically controlled Xe circulation & purification panel thermosyphon lines (3) charcoal column Xe recovery pumps condenser sampling RGA graduate student gas control panel feed & recovery bottles
Former BaBar IR2 complex Repurposed electronics hut: LZ / liquid nobles test stand LSST Clean Room pump shed Xe storage
LZ / liquid nobles test stand LN thermosyphon and controls Phase I & II system test Re-furbished LUX Kr removal for R&D
Kr removal: reduction to 0.015 ppt ~ 10% pp solar ν 10 tons / 60 days @ 200 kg/day X 2 passes 500 mbar 500 SLPM He (Fluitron compressor) 16 kg 250 SLPM He (dry backing pump) 100 mbar thermosyphon Xe charcoal 500 kg LN cryocooler cooled Kr trap Xe/Kr chromatography filter 10 mbar 250 SLPM He (Roots booster) U sampling RGA 50 SLPM Xe 2 bar 80 bar Xe storage He feed/purge ~ 120 min Xe recovery Xe ~ 120 min condensers 200 kg capacity 24 hour cycle (per condenser) automation of all 3 cycles
Dark matter detection - exciting future Liquid xenon TPCs playing key role 300-day data set for LUX ~ 4-5x LZ approaches neutrino floor Summary WIMP nucleon cross section cm 2 WIMP nucleon cross section (cm 2 ) 10 39 10 40 10 41 10 42 10 43 10 44 10 45 10 46 10 47 10 48 10 49 10 50 10 40 10 41 10 42 10 43 10 44 10 45 10 46 7 Be Neutrinos PICO250-C3F8 SuperCDMS SNOLAB NEUTRINO C OHER ENT SCATTERING SuperCDMS Soudan CDMS-lite SuperCDMS Soudan Low Threshold XENON 10 S2 (2013) CDMS-II Ge Low Threshold (2011) 8 B Neutrinos (Green&ovals)&Asymmetric&DM&& (Violet&oval)&Magne7c&DM& (Blue&oval)&Extra&dimensions&& (Red&circle)&SUSY&MSSM& &&&&&MSSM:&Pure&Higgsino&& &&&&&MSSM:&A&funnel& &&&&&MSSM:&BinoEstop&coannihila7on& &&&&&MSSM:&BinoEsquark&coannihila7on& & CoGeNT (2012) CRESST CDMS Si (2013) DAMA EDELWEISS (2011) 1 10 100 1000 10 4 WIMP Mass GeV c 2 SIMPLE (2012) NEUTRINO COHERENT SCATTERING Atmospheric and DSNB Neutrinos 10 1 10 2 m WIMP (GeV/c 2 10 3 ) COUPP (2012) ZEPLIN-III (2012) CDMS II Ge (2009) SuperCDMS Soudan Xenon100 (2012) DarkSide 50 LUX Xenon1T DarkSide G2 DEAP3600 PICO250-CF3I LZ 10 3 10 4 10 5 10 6 10 7 10 8 10 9 10 10 10 11 10 12 10 13 10 14 WIMP nucleon cross section pb
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