directional dark matter detection · ciaran o’hare • assumptions • 3 years of running time...

DirectionalDarkMatterDetection

DMhalo

MilkyWay

SendaiSymposium,March2019SvenVahsen(UniversityofHawaii)

Outline

• ChallengesindirectdetectionofDM• Motivationfordirectionaldetectors• Technologicalapproaches• CYGNUS

Jan8th,2019 SendaiSymposium 2

DoweliveinaWIMPhalo?• DarkMatterexists

• OverwhelmingevidenceatdistancescalesfromMilkyWaytovisibleuniverse

• Allgravitational

• WIMPsareonehypothesis• DirectDetectionseekstoanswer

• DoesthelocalMilkyWayDMhalocontainWIMP-likeparticles?

• Whataretheirproperties?• Whatistheirlocaldensityandvelocitydistribution?

Jan8th,2019 SendaiSymposium

WIMPhalo?

MilkyWay

3

Challenges

• Hugedetectors• Stringentrequirementson

• Shielding• Radiopurity• Backgroundrejection

Jan8th,2019 SendaiSymposium

LUXdetector368kgLXe

Watershield

4

SI,elastic,WIMP/nucleonScattering:ExperimentalStatus

• Bestlimitsnow<0.1zB

• Nobleliquidexperimentsmostsensitiveatm~50GeV/c2

• Solidtargetsleadingaroundm~5 GeV/c2

• Controversialsignalssuggestingm~10GeV

Jan8th,2019 SendaiSymposium

C.O’hare

5

SD,elastic,WIMP/nucleonScattering:ExperimentalStatus• Bubblechamberswithfluorinetargetsaretakingthelead

• Excellentgammarejectionatlowenergies

Jan8th,2019 SendaiSymposium

Clark@UCLADM‘18

6

RecentLimits:Lowmass

• Ionization-onlyanalysesfromnobleliquidexperiments

• Dedicated,often,ionization-basedexperiments,includinggastargets

• Often• lackofparticleIDatlowest(keV)energies

• Uncertaintyaboutlow-energysensitivity

Jan8th,2019 SendaiSymposium

arxiv:1802.06994Darkside-50ionization(S2)onlyanalysisAnalysisthreshold:0.6keVnr

7

SummaryofStatusandChallenges

• G2experimentswillprobecross-sectionswithinfactor10-100oftheneutrinofloorform>1GeV/c2

• Challengestofurtherprogressinthismassrange• Irreducibleneutrinobackground• LackofparticleIDinionization-onlyexperimentsforE~<10keV• LingeringcontroversialsignalsfromDAMA/lackofcleardiscoverysignal• Calibrationsatlowestrecoilenergies• Everstricterrequirementsonradiopurityandbackgroundrejection

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MotivationforDirectionalDetectors

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Non-directionalWIMPsearch

• Observable:excesscountrateoverpredictedBGinsignalregion

• Requiresultra-cleandetectors&preciseunderstandingofremainingbackgrounds

• Single-scatteringneutronsproduceidenticaleventstoWIMPs

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Xenon100

10

TheWIMPWind

• ~220km/s• blowsfromCYGNUS• providestwoadditionalWIMPsignatures…

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AnnualRateModulation

• duetomotionofeartharoundsun• %-leveleffect• requiresthousandsofsignalevents,and%-levelcontrolofBGsandgain

Jan 8th, 2019 Sendai Symposium 12

Diurnal(Daily)DirectionalOscillation

Jan 8th, 2019 Sendai Symposium

• oscillationofthemeanrecoildirection,duetorotationofearth• order1effect• oscillationperiod= siderealday≠ solarday• noknownbackgroundwiththissignature

WIMPwind

~42o

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TheGalacticDipole

• Thediurnaldirectionaloscillationisequivalenttoadipoleingalacticcoordinates

• RecoilsPointawayfromconstellationCYGNUS

• Need~103Dvectoreventstorejectisotropy.

Jan 8th, 2019 Sendai Symposium

Physics Reports 627 (2016)

CYGNUS

Galacticdipole:- strongestpredicteddirectdetectionsignature- canunambiguouslydemonstratecosmologicaloriginofsignal

14

Penetratingtheneutrinofloor

• DirectionalitysignificantlyenhancestheDMsensitivitybelowneutrinofloor

• 3Dagain“best”

• Butnote:• TrueFigureofMerit:sensitivity/unitcost

• Arealisticdetectorhasstronglyenergy-dependentdirectionality.Thiswasnotconsideredinpaststudies.

Jan 8th, 2019 Sendai Symposium

Readout strategies for directional dark matter detection beyond the neutrino backgroundCiaran A. J. O'Hare, Anne M. Green, Julien Billard, Enectali Figueroa-Feliciano, Louis E. Strigari

CiaranA.J.O'Hare

15

TechnologicalApproaches

Jan8th,2019 SendaiSymposium 16

AchievingDirectionality

• Detectorsthatreconstructtherecoiltrajectory

• Gas-basedTPCs• NuclearEmulsions• Crystaldefectspectroscopy• DNAstranddetector• Planartargets(graphene)

• Detectorsthatindirectlydeterminetherecoildirection

• Anisotropicscintillators• Columnarrecombination• Carbonnanotubes

• Event-by-eventrecoiltrackingincondensedmatterishard,butnotimpossible

Jan8th,2019 SendaiSymposium

PhysicsReports662(2016)

Seenexttwotalks

17

PrototypesandExperimentsName Technology Directionality Status

NEWAGE Gas TPC,stripreadout 3d Runningunderground

DRIFT GasTPC,NID,wirereadout

1.5d Running underground

MIMAC GasTPC,stripreadout 3d Ran underground, scalingup

DMTPC GasTPC,opticalreadout

2d Ran underground, scaledup,stopped

D3 /HawaiireadoutR&D GasTPC,pixelreadout 3d Prototypesevaluated, ranabove-ground

NewMexicoreadoutR&D GasTPC,NID,opticalreadout

2d Prototypes evaluated

LEMON,ORANGE,INITIUM,CYGNO Gas TPCs, CMOS+PMTopticalreadout

3d Prototypesevaluated,funded toscaleup

NEWSdm NuclearEmulsions 2d Prototyping / going underground

PTOLEMY Graphene 2d Prototyping /going underground

Jan8th,2019 SendaiSymposium

Alldirectionalthathavesetlimitsuse<=1m3 gasTPCsNEWAGE:bestlimitusingdirectionalityDRIFT:bestlimitwithadirectionaldetector

(listisprobablynotcomprehensive!)

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CYGNUS

TheCYGNUSProto-Collaboration• Recently, many of the groups

working on directional dark matter detection formed CYNUS

• 45 signed members from the US, UK, Japan, Italy, Spain, China, Australia

• Steering group:• Neil Spooner (Sheffield, UK)• Sven Vahsen (Hawaii, USA)• Kentaro Miuchi (Kobe, Japan)• Elisabetta Baracchini (GSSI/INFN, Italy)• Elisabetta Barberio (Melbourne,

Australia)

Jan8th,2019 SendaiSymposium

ThedarkmatterwindisexpectedtocomefromtheconstellationCygnus.

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Themainidea• DirectDMdetectionw/GasbasedTPCs

• Measurespatialionizationdistributionresultingfromnuclearrecoils

• Advantages:• AxialDirectionality• Head/tail• Backgroundrejection

• ParticleID• 3Dfiducialization

• Technologicallychallenging,butnowachievableviamultipletechnologies

Jan8th,2019 SendaiSymposium

20keVeeelectron

20keVeeHe-recoil

10xlonger thanrecoil!

Initialionizationdistribution

chargecloudafter25cmdrift ingasTPC

DM

𝛄

21

CYGNUSvisionandlong-termgoal> 1000 m3 directional nuclear recoil detector capable of• Setting competitive DM limits• Observing galactic dipole ó diurnal oscillation in lab

• Detecting solar neutrinos• Efficiently penetrating the νfloor

• Measuring DM particle properties and physics

• Measuring Geoneutrinos• WIMP astronomy

Jan8th,2019 SendaiSymposium

CYGNUS

A review of the discovery reach of directional Dark Matter detectionPhysics Reports 627 (2016)

Galacticdipole: - strongestpredicteddirectdetectionsignature- unambiguous proofofcosmologicalorigin

exposure

22

CYGNUS:ExperimentalApproach

• Gas Time Projection Chamber• Gas mixture: SF6:4He, p~1 atm

• Possibility of switching between higher density (search mode) gas and lower density gas mixtures for (improved) directional confirmation of WIMP signal

• Reduced diffusion via negative Ion drift (SF6 gas)

• Redundant 3D fiducialization• SF6 minority carriers• charge cloud profile

• Helium target• Improved sensitivity to low mass WIMP• Longer recoil tracks, extending directionality

to lower energies• Multiple readout plane options have been

successfully demonstrated

Jan8th,2019 SendaiSymposium

WIMP

E

Erecoil(track)ionization

SF6:4He gas

gasvesselneutron+gammashielding

centralcathode

23

3DFiducialization I:MinorityCarriers

Jan8th,2019 SendaiSymposium

CS2-CF4-O2

AllBGremoved!

Discovery of Multiple, Ionization-Created Anions in Gas Mixtures Containing CS2 and O2Daniel P. Snowden-Ifft http://arxiv.org/abs/1308.0354

• GamechangerfordirectionalWIMPsearchviagasTPC• Utilizestiming- workswithanychargereadout(1D,2D,3D)• FirstdiscoveredinCS2• Nowalsodemonstrated inpureSF6 &CF4+SF6mixtures• Incrediblylucky:SF6 isalsonon-toxic,non-flammable, notcorrosive,

hasgain,thermaldiffusion, andisagoodSDtarget(!) 24

3DFiducialization II:ChargeCloudReconstruction

• Measuringcharge-profile(not width) oftrack,enablesaccuratemeasurementoftransversediffusion,whichdependsondriftlength

à obtainabsolutepositionindriftdirection

P.Lewis (U.Hawaii)

• Requireshighresolution readoutofchargedensityà only2D,3D• However, shouldworkwithanygas• Published versionutilized“chopped”alphas,buthassincebeen

extendedbygradstudent toalsoworkwithrecoilevents(unpublished)

Jan8th,2019 SendaiSymposium 25

2Delectronrejection(experiment)• Onright:2Dopticalreadoutin100torr CF4

• Fversuselectronrecoils• 𝜎 =0.35mmreadoutresolution,incl.diffusion• Usingrange-energysignature,electroneventrejectionfactor<3.9x

10-5 around10keVee• It’salimit– allavailableelectroneventsrejected!

• ExtrapolatingtoCYGNUS• 20torr SF6+740torr Helium:50%longertracks• 50cmofthermaldrift(𝜎 =0.55mm):50%higher

àexpectedsamediscriminationinCYGNUS• Shouldimprovewith3Dchargecloudtomography,i.e.,goingbeyondrange-energysignature.

• Follow-upexperimentalworkwith3Dreadoutneeded.• BothdirectionalityandBGrejectionarestronglygasdensitydependent.Canoperateinsearchmode(higherdensity)andconfirmationmode(lowerdensity)

Jan8th,2019 SendaiSymposium

GEM

-basedTPCwith

CCD

imagingford

irectionaldarkmatterd

etectio

nN.S.Phan,et.al.,AstroparticlePhysics,84(2016)

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SixtypesofTPCchargereadouts

Jan8th,2019 SendaiSymposium

WorseperformanceLowercost

BetterperformanceHighercostBestcompromise?Simulationstudytofindout

6− 4− 2− 0 2 4 6x [cm]6−

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6− 4− 2− 0 2 4 6x [cm]6−

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6− 4− 2− 0 2 4 6x [cm]

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1DGEM 1.5D:wires 3Dpads 2Doptical 3Dstrips 3Dpixels

20keV electronafter25cmofdrift

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InputParameters:Diffusion,gain,etc

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InputParameters:Readouts

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Results:Detectionefficiency

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Ok,butNIDgainonlowsideCCDandplanarsuffersfromthis

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F He

Results:AxialVectorAngularresolution

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F He

• Lowerisbetter• Detectorispressure/diffusion limited• F:bad• He:better• Pixelsclosetooptimal• Stripsnotbad

31

Results:Head/tailrecognitionefficiency

Jan8th,2019 SendaiSymposium

• Higher isbetter• Detectorisdiffusion/pressure limited

• especiallyforF• He:better

• onlypixels,strip,andCCDdoOK

F He

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Results:3DElectronRejectionFactors

Jan8th,2019 SendaiSymposium

• Nice!• Getssomewhatworseafter

diffusion• Algorithm canbeimproved

F He

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FinalResult:SensitivityperUnitCost

Jan8th,2019 SendaiSymposiumConclusion/recommendation: builda1000m3detectorwithstrip readout for$35M 34

10-1 100 101 102 103 10410-4710-4610-4510-4410-4310-4210-4110-4010-3910-3810-3710-3610-3510-34

CYGNUSSDSensitivity

• Assumptions• 3 years of running time• 3 keVr F threshold• 1 keVr He threshold• Directional mode:

20 torr SF6740 torr 4-He

• Search mode:200 torr SF6740 torr 4-He

• Should see solar 𝜈 events• Discoveries can be

investigated in directional mode

Jan8th,2019 SendaiSymposium

preliminary

CiaranO’Hare

CYGNUS 1000: 10m x 10m x 10m CYGNUS 100k: ~2 x DUNE target volume

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10-1 100 101 102 103 10410-5110-5010-4910-4810-4710-4610-4510-4410-4310-4210-4110-4010-3910-3810-3710-36

CYGNUSSISensitivity

Jan8th,2019 SendaiSymposium

preliminary

CiaranO’Hare

• Assumptions• 3 years of running time• 3 keVr F threshold• 1 keVr He threshold• Directional mode:

20 torr SF6740 torr 4-He

• Search mode:200 torr SF6740 torr 4-He

• Should see solar 𝜈 events• Discoveries can be

investigated in directional mode

36

SendaiSymposium 37

Summary• Manynovelideasforachievingdirectionalityhavebeenproposedandstudied• MuchoftheworldwidedirectionaldetectioncommunitymergedintoCYGNUS• WorkonstrawmandesignofCYGNUS1000gas-TPCdetectornearlycomplete

• CompetitiveSIandSDsensitivity.ExtendstolowWIMPmassesthankstoHe

• CYGNUS1000wouldbethefirststeptowardsalarge-scale,distributedrecoilobservatory,capableof

• unambiguouslydemonstratingthecosmologicaloriginofaputativeWIMPsignal• effectivelypenetratingtheneutrinofloor• eventually,WIMPastronomy

• Pleasejoin:DirectionalDetectionWorkshopinRoma(Italy)atSapienzaon June 24-25-26th2019.

Jan8th,2019 SendaiSymposium 38