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The LUX Dark Matter Search Status Update

Sixth TPC Symposium – Paris – December 17 th , 2012. The LUX Dark Matter Search Status Update. Exciting times in South Dakota. University of Edinburgh. UC Davis. University of Maryland. University College London. The LUX Collaboration. Brown. SD School of Mines. Texas A&M. Case Western.

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The LUX Dark Matter Search Status Update

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  1. Sixth TPC Symposium – Paris – December 17th, 2012 The LUX Dark Matter SearchStatus Update Exciting times in South Dakota

  2. University of Edinburgh UC Davis University of Maryland University College London The LUX Collaboration Brown SD School of Mines Texas A&M Case Western Imperial College London Collaboration Meeting, UCSB March 2012 UC Santa Barbara Lawrence Berkeley + UC Berkeley Yale University of Rochester Lawrence Livermore University of South Dakota LIP Coimbra

  3. The LUX Experiment Thermosyphon Copper shield Water tank Top PMT array Anode grid PTFE reflector panels and field cage Detector stand Outer cryostat Inner cryostat Cathode grid • 370 kg xenon • 300 kg active region • 100 kg fiducial • 122 PMTs 2” round • Low-background Ti cryostat Bottom PMT array

  4. 2.75 m 3.50 m 1.20 m m neutrons Rock neutrons Rock g Inverted steel pyramid 0 1 2 3 4Shield Thickness (m) LUX Design – Water Tank • Water Tank: d = 8 m, h = 6 m • 300 tonnes, 3.5 m thickness on the sides • Inverted steel pyramid (20 tonnes) under tank to increase shielding top/bottom • Cherenkov muon veto • Ultra-low background facility • Gamma event rate reduction: ~10-9 • High-E neutrons (>10 MeV): ~10-3 Rendering by J. Thomson Slide design from L de Viveiros

  5. LUX Design – Deep Underground Operation Cosmic Rays - Muons

  6. LUX Design – Self-shielding

  7. LUX – XENON100 Comparison Comparison of LUX and XENON100 data for the same exposure of 7600 kg.d, from the latest XENON100 result (July 2012). LUX data is simulated from known radioactive background components. The WIMP signal in red corresponds to a 100 GeV/c2 WIMP with a cross-section at the current best sensitivity limit of 2.5 10-45 cm2. The ER background is one order of magnitude lower, allowing for a clearer detection signal or a stronger limit.

  8. The LUX Program 2012+ 2007 – 2009 2010 – 2011

  9. Surface Lab – June 2009 to September 2010 • Full-scale test of LUXdeployment • Liq/gas system • PMT testing • DAQ testing • Water shield • Xe purity June 2009 September 2010

  10. Surface Lab – August 2010 to February 2011

  11. Surface Lab – May 2011 : Run 1 Cryogenic Test: Success!

  12. Surface Lab – July to October 2011

  13. Surface Lab – October 2011 to February 2012 : Run 2 Position resolution < 5mm 205 ms ~ 25 cm = ½ a LUX Leak!

  14. LUX Run 2 Summary • List of major achievements already communicated to the World by February 2012 • To which one can add: Working slow-control and alarm system, working muon veto, emergency storage system in place, working calibration system (external and internal), reviewed and tested operating and assembly procedures, no (work related) injuries over 17 months and > 38,500 total work hours… • Negative points: • Leak in condenser line limited purification capability (easily fixed) • One PMT base stopped working (out of 122; now fixed) • Used ~20-30 kg more Xenon to fill detector than anticipated (we have a lot to spare now) • Drift field limited by flaws on Cathode grid wires (now replaced and tested) • Did not find Dark Matter (neither did anyone else… probably) 120 V / cm (limited by electroluminescence on grid)

  15. Surface Lab – March to July 2012

  16. Sanford Lab – Davis Laboratory Clean Room Breakout Control Room LN Storage Electronics Counting Facility Xe Balloon LUX Detector Cherenkov Water tank Excavation/construction started August 2009finished June 2012 Gas System

  17. Davis Campus – Summer 2012 June 25 July 6 June 29 June 15 August 25 July 12

  18. Davis Campus – September 2012

  19. LUX Underground Physics Program • Oct 22 – Nov 7: Water Tank filled with water • Oct 1 – Dec 6: Detector at vacuum • Cherenkov data from PMT windows, PTFE • Dec 7 – Jan 13: Detector warm with Xe gas • Alpha events from Rn on internal surfaces • Kr-83 for gas flow tomography • Jan 14 – Feb 13: Cool-down + Condense Xe • 400 kg of Xe with 5 ppt measured Kr is ready • ~1 month to reach acceptable Xe purity • ~2 months of non-blind WIMP search • Including run parameters optimization • ~1 month of additional calibrations •  First result by mid-2013 PTFE Cherenkov events Nov 7 October 22

  20. LUX WIMP Sensitivity Goal CDMS II 2008 ZEPLIN III 2011 Edelweiss II 2011 XENON100 2011 = LUX 4 days XENON100 2012 = LUX 15 days LUX 300 days

  21. Because this was not long enough already… Additional Slides

  22. LUX Design – Dual Phase Xenon TPC • Can measure single electrons and photons • Charge yield reduced for nuclear recoils • Excellent 3D imaging • Reject multiple scatters • Eliminate edge events to take advantage of Xe self shielding

  23. LZ Program – Overview • Born from the joining of LUX and ZEPLIN • Construction 2014-2016 • Run 2016- 2019 (…?) • New features compared to LUX • Increased Xe mass : 7t total, 5t fiducial • 482 3" PMTs at ~1 mBq radioactivity level • Liquid Scintillator shield/veto • Instrumented « dead » Xe space • Improved Cherenkov veto coverage • ...That’s it. Progress in sensitivity comes chiefly with: • Increasing the Xe mass • Scaling up existing LUX technology • Xe self-shielding is driving the background rates down dramatically • R&D effort ramping up since 2011, Project Management through LBNL LZ uses the same water tank as LUX in the Davis Lab

  24. LZ Program – WIMP Sensitivity Reach XENON100 2012 LUX 300 days x 7 LZ 1000 days x 175

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