DARK MATTER SEARCH Carter Hall, University of Maryland

Direct detection of WIMP dark matter~ 300 proton massesper liter of space.

If MWIMP ~ 100 GeV,then 3 WIMP/liter.

Typical orbital velocity~ 230 km/sec, or 0.1% speed of light.

Coherent scaler interactions:~ A2

Rate < 1 event / kg / 100 days, or much, much lower

Its not difficult to shield at 10 keVtypical WIMP recoil energiesGamma interaction cross sectionOnly MeV gs can penetrate,but only keV gs can fake a WIMP

Self-shielding of liquid xenon is extremely powerfulFiducial volume cut rejects most backgrounds

Sensitivity improves quickly as target mass increases!Self-shielding effect~MeV g~keVscatteringevent forwardscatteringmustcross full volumewithoutscatteringagain

Particle ID: nuclear recoil discriminationIonization-to-scintillation ratio allows discrimination between common radioactivity and WIMP events.Background rejection factor of ~180

The Hunters HutHomestake (SD)

2002 Homestake Solar Neutrino Experiment

Davis Cavern @ Homestake, September 2009

Davis Cavern @ Homestake, March 2011

LUX Detector - OverviewGaitskell - Brown University / LUXTitanium VesselsDodecagonal field cage + PTFE reflector panelsPMT holding copper platesCounterweightFeed-throughs for cables / pipesLN bath columnRadiation shield49 cm59 cmCathode gridAnode grid

LUX Surface Facility @ Homestake

LUX 350 kg detector under assembly

LUX 350 kg detector under assembly

Test deployment of LUX in the Surface Facility Water Tank April 2010

Test deployment of LUX in the Surface Facility Water Tank April 2010Cryostat successfully cooled to liquid xenon temperature May 2010

New analytic technique to detect krypton at the part-per-trillion levelarXiv:1103.2714v1

Detect electronegative impurities at less than a part-per-billionopen leak valve,bypass gas purifierflow through gas purifierbypassgas purifierXe is constant due to cold trap18 ppb N25 ppb O20.25 ppb CH4close leakvalve to measurebackgrounds~few ppm ArarXiv:1002.2742

Experiment to test removal of tritiated methaneXe proportional tubefor tritium countingXe purifier > 99.9% of CH3T removed in one pass Liquid Xenon removal test in this summerCH3T storage bottleFE-55 x-raycalibration

Thermosyphon cooling system

Xenon Purity measured in a 60 kg test run ~9 hr time constant for purification

> 2 m electron drift length achieved (> 1000 us) with 60kg target

Errors dominated by use of 5 cm test cell drift within large cryostat

0.2 tonnes circulation per day

Heat Exchanger Operates >96% EfficientDemonstrated - 18 W required to circulate 0.4 tonnes of Xe a day Evaporate Liquid > Gas / Purification -> Re-condense Liquid

LUX dark matter sensitivityStatus: LUX is being now being tested on the surface at Homestake.Move underground in December 2011.

The LUX CollaborationBrownXENON10, CDMSCase WesternSNO, Borexino, XENON10, CDMSLawrence Berkeley + UC BerkeleySNO, KamLANDHarvardBABAR, ATLASLawrence LivermoreXENON10University of MarylandEXOSD School of MinesTexas A&MUC DavisDouble Chooz, CMSZEPLIN IIUniversity of RochesterU. South DakotaYaleZEPLIN IIMajorana, CLEAN-DEAPXENON10, CLEAN-DEAPIceCubeCollaboration meeting, Homestake, March 2010Formed in 2007, fully funded DOE/NSF in 2008

Richard GaitskellPI, ProfessorSimon FiorucciPostdocMonica PangilinanPostdocLuiz de ViveirosGraduate StudentJeremy ChapmanGraduate StudentCarlos Hernandez FahamGraduate StudentDavid MallingGraduate StudentJames VerbusGraduate Student

Thomas ShuttPI, ProfessorDan AkeribProfessorMike DragowskyResearch Associate ProfessorCarmen CarmonaPostdocKen ClarkPostdocKaren GibsonPostdocAdam BradleyGraduate StudentPatrick PhelpsGraduate StudentChang LeeGraduate Student

Bob JacobsenProfessorStu LokenProfessorJim SiegristProfessorJoseph RassonEngineerMia ihmGrad Student

Masahiro MoriiProfessorMichal WlasenkoPostdoc

Adam BernsteinPI, Leader of Adv. Detectors GroupDennis CarrSenior EngineerKareem KazkazStaff PhysicistPeter SorensenPostdoc

Xinhua BaiProfessorMark HanardtUndergraduate Student

Frank WolfsProfessorUdo ShroederProfessorWojtek SkutskiSenior ScientistJan TokeSenior ScientistEryk DruszkiewiczGraduate Student

James WhiteProfessorRobert WebbProfessorRachel ManninoGraduate StudentTyana StieglerGraduate StudentClement SofkaGraduate Student

Mani TripathiProfessorRobert SvobodaProfessorRichard LanderProfessorBritt HollbrookSenior EngineerJohn ThomsonEngineerMatthew SzydagisPostdocJeremy MockGraduate StudentMelinda SweanyGraduate StudentNick WalshGraduate StudentMichael WoodsGraduate Student

Carter HallProfessorDouglas LeonardPostdoc

Daniel McKinseyProfessorJames NikkelResearch ScientistSidney CahnResearch ScientistAlexey LyashenkoPostdocEthan BernardPostdocLouis KastensGraduate StudentNicole LarsenGraduate Student

DongMing MeiProfessorWengchang XiangPostdocChao ZhangPostdocJason SpaansGraduate StudentXiaoyi YangGraduate Student