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


LUXdetector368kgLXe

Watershield

4

SI,elastic,WIMP/nucleonScattering:ExperimentalStatus

• Bestlimitsnow<0.1zB

• Nobleliquidexperimentsmostsensitiveatm~50GeV/c2

• Solidtargetsleadingaroundm~5 GeV/c2

• Controversialsignalssuggestingm~10GeV


C.O’hare

5

SD,elastic,WIMP/nucleonScattering:ExperimentalStatus• Bubblechamberswithfluorinetargetsaretakingthelead

• Excellentgammarejectionatlowenergies


Clark@UCLADM‘18

6

RecentLimits:Lowmass

• Ionization-onlyanalysesfromnobleliquidexperiments

• Dedicated,often,ionization-basedexperiments,includinggastargets

• Often• lackofparticleIDatlowest(keV)energies

• Uncertaintyaboutlow-energysensitivity


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

7

SummaryofStatusandChallenges

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

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


MotivationforDirectionalDetectors


Non-directionalWIMPsearch

• Observable:excesscountrateoverpredictedBGinsignalregion

• Requiresultra-cleandetectors&preciseunderstandingofremainingbackgrounds

• Single-scatteringneutronsproduceidenticaleventstoWIMPs


Xenon100

10

TheWIMPWind

• ~220km/s• blowsfromCYGNUS• providestwoadditionalWIMPsignatures…

Jan 8th, 2019 Sendai Symposium 11

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

13

TheGalacticDipole

• Thediurnaldirectionaloscillationisequivalenttoadipoleingalacticcoordinates

• RecoilsPointawayfromconstellationCYGNUS

• Need~103Dvectoreventstorejectisotropy.


Physics Reports 627 (2016)

CYGNUS

Galacticdipole:- strongestpredicteddirectdetectionsignature- canunambiguouslydemonstratecosmologicaloriginofsignal

14

Penetratingtheneutrinofloor

• DirectionalitysignificantlyenhancestheDMsensitivitybelowneutrinofloor

• 3Dagain“best”

• Butnote:• TrueFigureofMerit:sensitivity/unitcost

• Arealisticdetectorhasstronglyenergy-dependentdirectionality.Thiswasnotconsideredinpaststudies.


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


AchievingDirectionality

• Detectorsthatreconstructtherecoiltrajectory

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

• Detectorsthatindirectlydeterminetherecoildirection

• Anisotropicscintillators• Columnarrecombination• Carbonnanotubes

• Event-by-eventrecoiltrackingincondensedmatterishard,butnotimpossible


PhysicsReports662(2016)

Seenexttwotalks

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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


Alldirectionalthathavesetlimitsuse<=1m3 gasTPCsNEWAGE:bestlimitusingdirectionalityDRIFT:bestlimitwithadirectionaldetector

(listisprobablynotcomprehensive!)

18

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)


ThedarkmatterwindisexpectedtocomefromtheconstellationCygnus.

20

Themainidea• DirectDMdetectionw/GasbasedTPCs

• Measurespatialionizationdistributionresultingfromnuclearrecoils

• Advantages:• AxialDirectionality• Head/tail• Backgroundrejection

• ParticleID• 3Dfiducialization

• Technologicallychallenging,butnowachievableviamultipletechnologies


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


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


WIMP

E

Erecoil(track)ionization

SF6:4He gas

gasvesselneutron+gammashielding

centralcathode

23

3DFiducialization I:MinorityCarriers


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)


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)


GEM

-basedTPCwith

CCD

imagingford

irectionaldarkmatterd

etectio

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

26

0 1 2 3 4 5z [cm]

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SixtypesofTPCchargereadouts


WorseperformanceLowercost

BetterperformanceHighercostBestcompromise?Simulationstudytofindout

6− 4− 2− 0 2 4 6x [cm]6−

4−2−

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y [cm]0

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6− 4− 2− 0 2 4 6x [cm]6−

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m]

6− 4− 2− 0 2 4 6x [cm]

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3− 2− 1− 0 1 2 3x [cm]6−

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3− 2− 1− 0 1 2 3x [cm]6−

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3− 2− 1− 0 1 2 3x [cm]6−

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m]

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

20keV electronafter25cmofdrift

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InputParameters:Diffusion,gain,etc


InputParameters:Readouts


Results:Detectionefficiency


Ok,butNIDgainonlowsideCCDandplanarsuffersfromthis

30

F He

Results:AxialVectorAngularresolution


F He

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

31

Results:Head/tailrecognitionefficiency


• Higher isbetter• Detectorisdiffusion/pressure limited

• especiallyforF• He:better

• onlypixels,strip,andCCDdoOK

F He

32

Results:3DElectronRejectionFactors


• Nice!• Getssomewhatworseafter

diffusion• Algorithm canbeimproved

F He

33

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


preliminary

CiaranO’Hare

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

35

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

CYGNUSSISensitivity


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.


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

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