LUX: Shedding Light on Dark Matter Adam Bradley Case Western Reserve University Great Lakes Cosmology Workshop 8 June 2, 2007

Outline Give outline Give talk End talk Answer (easy) questions Basics Galactic WIMP DM / general rare events detection Liquid noble-gas detectors TPCs and scaling LXe Current DM sensitivities LUX in all its glory Give talk End talk Answer (easy) questions January 15, 2019 A. Bradley; GLCW8, the OSU

The Basics Fritz Zwicky, Vera Rubin, et al… WMAP, SDSS, etc… Weak scale energies SUSY - neutralino January 15, 2019 A. Bradley; GLCW8, the OSU

Rate: < 0.06 event/kg/day, or much lower Detecting galactic WIMP dark matter Dark matter “Halo” surrounds all galaxies, including ours. ρ ∼ 300 mproton liter Density at Earth: mwimp ~ 100 mproton. 3 WIMPS/liter! Typical orbital velocity: v ≈ 230 km/s ~ 1/1000 speed of light Coherent scalar interactions: A2 Rate: < 0.06 event/kg/day, or much lower January 15, 2019 A. Bradley; GLCW8, the OSU

Detecting rare events. µ Shield against outside backgrounds Problem: radioactivity Ambient: 100 events/kg/sec. Pure materials in detector Shield against outside backgrounds Underground to avoid muons WIMP detector January 15, 2019 A. Bradley; GLCW8, the OSU

Liquid Noble-Gas Detectors Liquid target: Readily purified Scalable to large masses Liquid scintillator: 14C fatal for dark matter Even in petroleum - 10-18 14C: U->a + rock -> n -> 14N(n,p)14C Liquid noble gasses. Easily purified. Scintillation and Ioinization Cryogenic PMTs exist. Xe: 165 K, λ=175 nm Ar: 87.3 K, λ =128 nm, 39Ar - 1 Bq/kg. Ne: 27.1 K, λ =80 nm, bubbles -> slow charge drift Scalable to large masses! January 15, 2019 A. Bradley; GLCW8, the OSU

Dual phase time projection chamber PMTs LXe WIMP Time Primary 5 µs/cm ~40 ns width ~1 µs width - Ed Es - Can measure single electrons and photons. Charge yield reduced for nuclear recoils. Good 3D imaging Eliminating edges crucial. A. Bolozdynya, NIMA 422 p314 (1999). January 15, 2019 A. Bradley; GLCW8, the OSU

Scaling liquid Xe to large masses Predictions from analytical calculation Enormous gains from self shielding above ~ 100 kg For very large mass, reduction in background, or increase in discrimination increases fiducial fraction January 15, 2019 A. Bradley; GLCW8, the OSU

Current Dark Matter Sensitivities Edelweiss I ZEPLIN II CDMS II WARP LUX (Proj) SuperCDMS@Soudan SuperCDMS@SNOLab XENON10 [070400] We have entered phase of testing SUSY. Need ton-scale detectors for full “generic” test. January 15, 2019 A. Bradley; GLCW8, the OSU

LUX Dark Matter Experiment - Summary Brown, Case, LLNL, LBNL, Rochester, Texas A&M, UC Davis, UCLA XENON10, ZEPLIN II (US) and CDMS; ν Detectors (Kamland/SuperK/SNO/Borexino); HEP/γ-ray astro (Also ZEPLIN III Groups after their current program completed) 300 kg Dual Phase LXe TPC with 100 kg fiducial >99% ER background rejection for 50% NR acceptance, E>10 keVr (Case+Columbia/Brown Prototypes + XENON10 + ZEPLIN II) 3D-imaging TPC eliminates surface activity, defines fiducial Backgrounds: Internal: strong self-shielding of PMT activity γ/β < 7x10-4 /keVee/kg/day, from PMTs (Hamamatsu R8778 or R8520). Neutrons (α,n) & fission subdominant External: large water shield with muon veto. Very effective for cavern γ+n, and HE n from muons Very low gamma backgrounds with readily achievable <10-11 g/g purity. DM reach: 2x10-45 cm2 in 4 months Possible ~5x10-46 cm2 reach with recent PMT activity reductions, longer running. January 15, 2019 A. Bradley; GLCW8, the OSU

LUX program: exploit scalability LUX detector LUXcore LUXcore: Final engineering for large-scale detector Cryostat, >100 kV feedthrough, charge drift, light collection over large distance Full system integration, including ~1m water shield 40 kg narrow “core”, 14 PMTs, 20 cm Ø x 40 cm tall. Radial scale-up requires full-funding. Under construction; operations at Case: summer 2007. LUX Experiment LUX in ~ 6m Ø water shield Very good match to early-implementaion DUSEL (e.g., Homestake “Davis” cavern) System scalable to very large mass. January 15, 2019 A. Bradley; GLCW8, the OSU

Summary The search for WIMP DM is on and heating up! Use of liquid noble-gas detectors gaining momentum “Easy” to use and scale LUX is here! “Let there be light (on WIMP DM)!” January 15, 2019 A. Bradley; GLCW8, the OSU