DARK MATTER DARK MATTER SEARCHSEARCH

Carter Hall, University of MarylandCarter Hall, University of Maryland

Direct detection of WIMP dark matter

00 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

It’s not difficult to shield at 10 keV

typical WIMP recoil energies

Gamma interaction cross section

Only MeV ’s can penetrate,but only keV ’s can

fake a WIMP

Self-shielding of liquid xenon is extremely powerful

Fiducial volume cut rejects most backgrounds

Sensitivity improves quickly as target mass increases!Self-shielding effect

~MeV

~keVscatteringevent – forward

scattering

mustcross

full volumewithout

scatteringagain

Particle ID: nuclear recoil discrimination

Ionization-to-scintillation ratio allows discrimination between common radioactivity and WIMP events.

Background rejection factor of ~180

The Hunters HutThe Hunters Hut Homestake (SD)Homestake (SD)

2002 2002

Homestake Solar Neutrino Experiment

Davis Cavern @ Homestake, September 2009

Davis Cavern @ Homestake, March 2011

Gaitskell - Brown University / LUX

LUX Detector - Overview

Titanium Vessels

Dodecagonal field cage+ PTFE reflector panels

PMT holding copper plates

Counterweight

Feed-throughs for cables / pipesLN bath column

Radiation shield

49 cm

59 cm

Cathode grid

Anode 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 2010

Cryostat successfully cooled to liquid xenon temperature – May 2010

1.5 ppt Kr

open leak valve

New analytic technique to detect krypton at the part-per-trillion level

arXiv:1103.2714v1

Detect electronegative impurities at less than a part-per-billion

open leak valve,bypass gas purifier

flow through flow through gas purifiergas purifier

bypassbypassgas purifiergas purifier

Xe is constant due to cold trap

18 ppb N2

5 ppb O2

0.25 ppb CH4

close leakclose leakvalve to measurevalve to measure

backgroundsbackgrounds

~few ppm Ar

arXiv:1002.2742

Experiment to test removal of tritiated methane

Xe proportional tubefor tritium counting Xe purifier

• > 99.9% of CH3T removed in one pass• Liquid Xenon removal test in this summer

CH3T storage bottle

FE-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

dayEvaporate Liquid > Gas / Purification -> Re-condense Liquid

LUX dark matter sensitivity

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

The LUX Collaboration

Richard Gaitskell PI, ProfessorSimon Fiorucci PostdocMonica Pangilinan PostdocLuiz de Viveiros Graduate StudentJeremy Chapman Graduate StudentCarlos Hernandez Faham Graduate StudentDavid Malling Graduate StudentJames Verbus Graduate Student

Brown XENON10, CDMS

Thomas Shutt PI, ProfessorDan Akerib ProfessorMike Dragowsky Research Associate ProfessorCarmen Carmona PostdocKen Clark PostdocKaren Gibson PostdocAdam Bradley Graduate StudentPatrick Phelps Graduate StudentChang Lee Graduate Student

Case Western SNO, Borexino, XENON10, CDMS

Bob Jacobsen ProfessorStu Loken ProfessorJim Siegrist ProfessorJoseph Rasson EngineerMia ihm Grad Student

Lawrence Berkeley + UC BerkeleySNO, KamLAND

Masahiro Morii ProfessorMichal Wlasenko Postdoc

Harvard BABAR, ATLAS

Adam Bernstein PI, Leader of Adv. Detectors GroupDennis Carr Senior EngineerKareem Kazkaz Staff PhysicistPeter Sorensen Postdoc

Lawrence Livermore XENON10

University of Maryland EXO

Xinhua Bai ProfessorMark Hanardt Undergraduate Student

Frank Wolfs ProfessorUdo Shroeder ProfessorWojtek Skutski Senior ScientistJan Toke Senior ScientistEryk Druszkiewicz Graduate Student

James White ProfessorRobert Webb ProfessorRachel Mannino Graduate StudentTyana Stiegler Graduate StudentClement Sofka Graduate Student

Mani Tripathi ProfessorRobert Svoboda ProfessorRichard Lander ProfessorBritt Hollbrook Senior EngineerJohn Thomson EngineerMatthew Szydagis PostdocJeremy Mock Graduate StudentMelinda Sweany Graduate StudentNick Walsh Graduate StudentMichael Woods Graduate Student

SD School of Mines

Texas A&M

UC Davis Double Chooz, CMS

ZEPLIN II

Carter Hall ProfessorDouglas Leonard Postdoc

Daniel McKinsey ProfessorJames Nikkel Research ScientistSidney Cahn Research ScientistAlexey Lyashenko PostdocEthan Bernard PostdocLouis Kastens Graduate StudentNicole Larsen Graduate Student

DongMing Mei ProfessorWengchang Xiang PostdocChao Zhang PostdocJason Spaans Graduate StudentXiaoyi Yang Graduate Student

University of Rochester

U. South Dakota

Yale

ZEPLIN II

Majorana, CLEAN-DEAP

XENON10, CLEAN-DEAP

IceCube

Collaboration meeting, Homestake, March 2010Collaboration meeting, Homestake, March 2010

Formed in 2007, fully funded DOE/NSF in 2008