“Whither WIMPs:” Direct Detection of SUSY Cold Dark...

transcript

Gaitskell

“Whither WIMPs:”Direct Detection of SUSY

Cold Dark Matter

Rick Gaitskell

Brown University, Department of Physics

useful information at http://gaitskell.brown.edu/

http://cdms.brown.edu/

One Tonne - Have we got what it takes?

Report To NFAC Committee July 25,2002

NFAC 25 July 2002 Rick Gaitskell

Dark Matter Experiments (Worldwide)(Running/Active Collaboration)

CsIANAIS Rosebud

DRIFT I

ZEPLIN II

ZEPLIN IIIZEPLIN I

Picasso

France Germany

DAMA LIBRA

CRESST II

Edelweiss II

Russia

Switzerland

Majorana(DM)

CDMS II

Simple

CanadaTaiwan

XMASS(DM)

Elegant V&VI

Orpheus

HDMS/Genino

Cuoricino

Dark Matter Experiments - By SiteSite Experiment Technique Target StatusBaksan (Russia) IGEX Ionisation 3kg Ge OperationalBern (Switzerland) ORPHEUS SSD 0.5kg Sn OperationalBoulby (UK) NaI

NaIADZEPLIN IZEPLIN II/IIIZEPLIN-MAXDRIFT-IDRIFT-10

ScintillatorScintillatorScintillatorScintillator/IonisationScintillator/IonisationTPCTPC

5kg NaI50kg NaI5kg Lxe30kg/7kg Xe1000kg Xe0.2kg CS22kg CS2

CompletedOperationalOperationalConstructionPlannedOperationalPlanned

Canfranc (Spain) COSMEIGEXANAISROSEBUD

IonisationIonisationScintillatorThermal

0.2kg Ge2.1kg Ge107kg NaIAl2O3,Ge,CaWO4

CompletedOperationalConstrcutionOperational

Frejus (France) Saclay-NaIEDELWEISS IEDELWEISS II

ScintillationThermal/IonisationThermal/Ionisation

10kg NaI0.07kg Ge1.3 kg Ge

CompletedCompletedOperational

Gran Sasso (Italy) Hdlberg/MscwHDMSGeniusDAMALIBRAXenonCRESST-ICRESST-IICUORICINOCUORE

IonisationIonisationIonisationScintillationScintillationScintillationThermalThermal/ScintillationThermalThermal

2.7kg Ge0.2kg Ge100kg Ge100kg NaI250kg NaI6kg Xe1kg Al2O310kg CaWO440kg TeO2760kg TeO2

CompletedOperationalPlannedOperationalConstructionOperationalOperationalConstructionConstructionPlanned

Kamioke (Japan) XMAS Scintillator/Ionisation 3 kg Xe1000 kg Xe

OperationalPlanned

Otto-Cosmo (Japan) Elegants VElegants VILiF

ScintillationScintillationThermal

NaICaF2LiF

OperationalOperationalOperational

Rustrel (France) SIMPLE SDD Freon OperationalStanford (USA) CDMS-1 Thermal/Ionisation 0.1kg Si, 1kg Ge CompletedSoudan (USA) CDMS-II

CryoArray

Phonons/Ionisation 0.3ks Si, 0.75kg Ge2 kg Si, 7 kg Ge100-1000 kg Ge

ConstructionConstructionPlanned

??? (USA) XENON Scintillator/Ionisation 1000 kg Xe PlannedSudbury (Canada) PICASSO SDD 1g Freon Operational

Talk Overview

• Cosmology & WIMPs in the Early Universe

• WIMPs in our own galaxy

• SUSY Framework

• DM Detection: History & Future Projections

• Highlight Selection of Current Detectors &Their Evolution

• Site Requirements & Backgrounds

• Summary

Neutralino Couplings

• Annihilation (many channels)u Spin Independent - Scalar

u Spin Dependent - Axial Vector

• Scattering from Nuclei (A nucleons)

u Spin Independent - Scalar

u Spin Dependent - Axial Vector

a.d.t.

Coherent s~A2 -->dominates

SUSY Calculations of s

• Broad Spectrum of Theorists Making WIMP Rate Predictionsu Using SUSY inspired frameworks, broad consistemcy in results

u Ellis, Ferstl, Olive; Baltz, Gondolo; Corsetti, Nath; Arnowitt, Nath; Mandic,Pierce, Gondolo, Muayama; Baer, Brhlik; Bednyakov, Klapdor-Kleingrothaus, Kovalenko; Bottino…

u Codes based on DarkSUSY and NeutDriver

• Predicted Range of Cross-Sectionsu Large range of SUSY space still allowed, SUSY mass scale uncertainty

feeds directly into s uncertainty

u UPPER LIMIT• Unable to make models consistent with DAMA signal, unless constraints on

Ωm>0.2 (<0.6) are relaxed. Lower abundance, raises allowed annihilation s

u LOWER LIMIT ?• Important experimentally! Sets maximum scale of discovery detector…

See Ellis, Ferstl, OlivePLB 532 (2002) 318 and refs therein

Plots on dmtools web site

SUSY Calculations/Experimental Input (2)

• Important Inputs from Existing Accelerator Constraintsu SUSY Search @LEP(final) mWIMP>50 GeV & mh (Lightest Higgs) >114 GeV

• Higgs constraints UPPER limit

u b->sg @CLEO (now doing K) / LEP(final)

u Muon g-2 @ BNL (Anomalous Magnetic Moment) - 1999 data• aµ=(g-2)/2, aµ(exp)-aµ(SM)=4.3 ±1.6 x 10-10, where aµmeasured ±1.3 ppm, theory ±

0.6ppm• Represents 1.6s away from Standard Model prediction (revised down from 2.6s

when SM theoretical calculation found to contain numerical sign error)• Provides strong LOWER LIMIT ON WIMP s for models with µ>0 (see next slide)

• Possible Future Influential Accelerator Datau BNL - New announcement coming Tuesday - 2000 data

• 2000 data (4 times existing set): expect an exp. error of 0.73-0.79 ppmIf new result for aµ(exp is same as previous will give 2.6s deviation from SMIf new result is consistent (@1s) with 1999 result then deviation could be in range 0-4s)

u (Novosebirsk e+e-)• Providing experimental rather than theoretical SM inputs to theoretical calc• Cuurent claim takes current 1.6s -> 2s effect

u Future analysis - 2001 data• Expect finish analysis ~end 2002 - reduced systematics vs 2000 since better frequency

choices• Experiement is becoming systematics dominated (little statistical improvement

possible)

u Tevatron (starting to run…)• SUSY discovery less likely• However, strong SUSY loop influence in b->bµµ decay channel G~(tanb)6

— Signal possible if tanb>30

u BBar/Belle (running)• Not likely, CP focus

u …LHC (Running by 2008)• Consider LHC as backstop for SUSY

• Sensitive to squarks&gluinos <2.5 TeV, m1/2~1 TeV, m0~1.5 TeV

• For discovery at LHC, chosen framework would have to imply mWIMP<500 GeVs

• Wide Range of Models Possible with current constraints

• If µ>0 (if g-2 results holds up, favours lower m1/2, m0 and µ>0) then…u Spin-independent sSI has range 6x10-8 - 2x10-10 pbu Spin-dependent sSD has range 10-5 - 2x10-7 pb

• If µ<0u Possible cancellation in SI interaction sSI ~ 0u Rely on SD interaction >10-8 pb

Current Experiments & SUSY Theory Range

~ 1 event/100 kg/yr

Edelweiss (June 2002)~0.25 event/kg/d

~1 event/kg/yr

http://dmtools.berkeley.edu

Direct Detection: History & Future

Oroville (88)

[m = ?? GeV - if significantly better limit obtained at different mass]

90% CL Limit on Cross section for 60 GeV WIMP (scalar coupling)

~1 event kg-1 day-1

~1 event kg-1 yr-1

~1 event 100 kg-1 yr-1

Not meant to be a complete list - see http://dmtools.berkeley.edu

Different ColoursIndicate Different

Technologies

011211.6.rjg

GeNaICryodet

(T) TargetSignal

Liq Xe

[m=20 GeV]Homestake (87)

H-M (94)H’berg-Moscow (98), IGEX (00)

DAMA (96)

UKDMC (96)[m=100 GeV]

DAMA (98) DAMA (00)

Gaitskell (astroph 0106200)

ZEPLIN I 6 kg Xe (T)

CDMS Soudan (T) 7 kg Ge+Si Cryodet

Majorana Phase 1 (T)GENINO (T) 100 kg Ge Diode

GENIUS (T)100 kg Ge Diode

CryoArray (T)0.1-1 tonne Cryodet

ZEPLIN II+III 10 kg Xe (T)

XENON / ZEPLIN 1t Xe (T)

CDMS SUF (99)

CDMS SUF (02)

Edelweiss (98)

Edelweiss (01)ZEPLIN I Xe (02)

Edelweiss (02)

Resolving Interpretation of DAMA Signal

• Positive Annual Modulation Signalu No other experiment <2004 able to check annual modu Except for DAMA upgrade 250 kg

• Improved light yield (NaI / PMT)• Lower background (factor ~ few)

u Would like to see revised acquisition strategy• Retain multiple events as control group• Direct Calibration of “signal” bin stability (g sources & LEDs)

• Assuming Scalar WIMPu s ~ A2 Cryogenic Ge

• CDMS I - neutron background limiting, but inconsistent with mod amp.— Require ~factor 3 lower limit to exclude all of 99% CL region at 90%

• Edelweiss already looking inconsistent ann mod. In 2002 look for ~10 kg-day exposure and zeroevents to rule out

• CDMS II - “First Dark” start end 2002

• Assuming ? particle (Not SUSY)u Require NaI target to remove uncertainties

• Anias(Spain) & NaAID(UK) programs aim to use pulse shape discrimination to surpass necessarysensitivity (DAMA do not plan to use PSD)

Key Points: Detectors, their environment & location

• Probable that we are witnessing the peak of worldwide diversity in DMu Current WIMP detection limit ~0.25 events/kg/day

(no WIMP-like events seen in ~10 kg-days exposure)

• Expect Rapid Progress in 2002-4 (based on assessment of currentprograms that are running, or in construction)

u Will be achieving large exposures with Zero Background Equivalent for ~100 kg-days

u Required scale may prohibit some new technology entering arena, unlesssupported by large engineering effort

• Challenges for next stage …

Key Points: Detectors, their environment & location (2)

• Greatest Challengesu Construction & Operation of Detector Arrays Underground

• Many of experiments experiencing “delays”

• All Groups would benefit greatly from infrastructure/support of Underground Lab

— Knowledgeable Technical/Engineering Assistance

u Achieving Detector Discrimination Performance (free systematics) (Demanding Background Discrimination >>99%)

u Improvements needed in Screening Facilities• Reduce Internal Radioactivity

• Current scale of typical collaboration has difficulty meeting all screeningrequirements

• Experiments >2005 clearly demand access to systems beyond simple HPGescreening

— Surface/low energy radioactivity screening (Providing Input to NUSL -> Screen Fac Initiative)

u Fabrication of some (internal) construction materials underground• Still being studied by groups

• Backgroundsu External Radioactivity Shielding

• Most dedicated (discriminating) WIMP experiments will use “traditional” shieldThis is not seen as a difficulty in larger experiments

— Pb for g‘s— Poly (H) to moderate external (a,n) neutrons (<10 MeV) from rock

• High Energy Neutrons from muons in rock are a concern (see next slide)

• Site Depth Requirementu Shallow ~1700 mwe (1 muons/m2/minute) will be satisfactory for compact (non-gas) targets

• Satisfactory for cosmogenic activation• Muons passing through detector array can be vetoed by simple muon veto

(>99% being achieved)• Muons outside muon veto will generate high energy neutrons (50-600 MeV) that cannot be

moderated directly using poly— A number of shielding strategies being developed, but they all involve “traditional”

technology— Additional cost of thick active shield will not dominate total cost - consensus— Without thick shield, HE neutrons events occur just below CDMS II level (1 event/100

kg/day)— Collaborations would like to develop Monte Carlos of full experiments

to ensure that goal of background <1 event/100 kg/year can be met

u Intermediate ~3800 mwe (Factor ~50x reduction in muons/HE neutrons)• Reduced thick shielding cost• Additional comfort factor, general consensus that 1 tonne experiments can function comfortably

wrt to HE neutrons from muons• Depth may be necessary for gas target given much large surface area to shield

u Deep ~6000 mwe (Further factor ~50x reduction in muon/HE neutrons)• Not currently on the road map - consensus “overkill”

High Energy (E>10 MeV) Neutrons from Muons

• Neutron production ~ Muon Fluxu With slight modification for

hardening of muon spectrum †

mean(Em)~ Depth0.47

†Aglietta et.al. Nuove Cimento 12, N4, page 467

Soudan

Si te* Not excavated(Multiple levels given in ft)

Relat iveMuonF lux

Relat iveNeutron

F lux >10 MeV

WIPP (2130 ft) x 65 x 45Soudan x 30 x 25Kamioke x 12 x 11Boulby x 4 x 4Gran SassoFrejus,Homestake (4860 ft)

x 1 x 1

Mont Blanc x 6-1 x 6-1

Sudbury x 25-1 x 25-1

Homestake (8200 ft) x 50-1 x 50-1

Key Points: Detectors, their environment & location (4)• Technologies have/are crossing over

u Detectors:• DBD decay• Solar Neutrino• Neutrino Magnetic Moment Searches

u Low background techniques/screening facilities:• Put in place structure for multi-user

Inter-Collaboration / Synergies: Dark Matter

• Dark Matter has new concerns, beyond those of Current Low BackgroundExperiments

u 0-100 keVu Surface Contamination

• This will require New Screening Strategiesu Studies/proposals underway in US (-> NUSL)

• Los Alamos / Princeton

• New Sources of Backgroundu Not just U / Th / Ku What are the phenomenologies?.. plate-out rates, materials preferences etc

• Low Background Materials Selectionu Database from previous and live experiments

• e.g. Just starting a database at Los Alamos (Tom Bowles), attached to NUSL

• Monte Carlosu Low Background Modeling NUSLib / BoulbyLib / GranSassoLib ?u GEANT4 - able to track down to 250 eV

List Created atAspen June 2002 DMWorkshop

Collaboration / Synergies: Dark Matter (2)

• Future Alignment with Demands of/Solutions from other experimentsu e.g. pp solar neutrino, DBD experiments

• Read-out Technologiesu Gas Readout Schemes

• MWPC / GEMs / MicroMegas

u Photo Detectors

u Cryogenic Detectors

• Field supported a diverse range of technologiesu Will it create difficulties when the necessary reintegration occurs for larger

experiments? Proto-collaborations of collaborations forming.

• Individual DM Experiments Benefit from Progress of Other DM Experimentsu c.f. John Nash

Collaboration / Synergies: Dark Matter (3)

• Support from International Laboratoriesu Intermediate Scale Experiments

• Not capable of bringing full resource requirements to hole in ground

u Probable that those labs providing best support will benefit… as will theexperiments drawn to best labs

WIMP SUSY Dark Matter Conclusion (1)

• Cosmology: Need for Non-Baryonic Dark Matter (Ω~0.2-0.3)• Current Direct Detection Experiments

u Testing some SUSY modelsu As sensitivity improves - will continue to test more models

• Recent/current accelerator constraints shrinking boundsu Mainly constrained UPPER bound of cross-sectionu g-2 can provide constraint on LOWER bound (for µ>0) if it remains statistically

significant

u DAMA 4s positive signal, is being/will be tested (need to rule out systematics)• in 2002 by CDMS and Edelweiss (both look incompatible at present for s~A2)• Anais(Spain) ~50 kg NaI (Pulse Shape Discrimination) in 2003/4• DAMA 250 kg upgrade (Ann Mod / Low backgrounds / Higher Light Yield)• Axial Vector (Spin Dependent) Quark-WIMP Couplings?

WIMP SUSY Dark Matter Conclusion (2)• Experimental Status

u Cryogenic experiments (reporting results)• Systematics increasingly well understood and dealt with (maturing technology)

— able to run @ zero signal contamination - Edelweiss 2002 (+ CDMS II detectors when moved to Soudan 2003 based on shallow site tests 80kg-days) + Others

— Scale up to ~10 kg targets in 2003/4

u Liquid Xe• ZEP I 3 kg fid. single phase currently running underground (Boulby)• ZEP II & III ~7 kg 2-phase (gas & liquid) being constructed - deploy 2003

— Performance data of “prototypes” used to assess ZEPLIN MAX~100 kg design• XMASS running 3 kg 2-phase underground (Kamioke)• XENON (funded) start prototype 7 kg -> design 100 kg module• Some, or all, of these groups may collaborate on next phase

u Gas TPC (Boulby) 1 m3 (u/g in 2001) -> 20 m3 (next phase 2004)• Awaiting data from u/g running• Target mass is a challenge: 1 m3 ~ 30 g Ge equiv. / Axis data difficult to fake

u HPGe• Main focus is DBD, but strong dark matter search component

u Plus a number of other experiments running underground

WIMP SUSY Dark Matter Conclusion (3)

• Subsequent Generations:u Studying Designs for sensitivity -> 1 event /100 kg/year s~10-46 cm2)

• Data from existing round of detectors will be used to inform design

u Target masses of 1 tonneu Support of Underground Laboratory will be vital for their successful

contruction and operationu <2008: just in time to scoop TeV / LHC SUSY signalu >2008: If signal is discovered then range of large detectors (different target

materials) can be used to study SUSY / Dark Matter physics

WIMP SUSY Dark Matter Conclusion• Cosmology: Need for Non-Baryonic Dark Matter (Ω~0.2-0.3)

• Current Direct Detection Experimentsu Testing some SUSY models, very close to top of region of broad agreement …u DAMA 4s positive signal, is being/will be tested (need to rule out systematics) …

• Future Experimentsu Cryogenic experiments

• Systematics increasingly well understood and dealt with (maturing technology)

u Liquid Xe (Boulby) First results from ZEPLIN IAwait deployment and performance data from ZEPLIN II+III

• ZEP I 3 kg fid. single phase currently running underground (Backgrounds)• ZEP II & III ~7 kg fid. gas & liquid phase discrimination (How good will discrimination be?)

u Gas TPC (Boulby) 1 m3 (u/g in 2001) -> 20 m3 (next phase 2004)

• Subsequent Generation: Move toward -> 1 event /100 kg/year s~10-46 cm2)u WIMP detectors: Target masses of 100 kg - 1 tonne (ZEPLIN / XENON / CryoArray)u ~6 years: just in time to scoop TeV / LHC SUSY signal

“Whither WIMPs:” Direct Detection of SUSY Cold Dark...

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