Diving for WIMPs:The Search for Dark Matter

in ANTARES

Lee F. ThompsonLee F. ThompsonUniversity of Sheffield, UKUniversity of Sheffield, UK

NIKHEF NIKHEF 28th January 200528th January 2005

CRIME ORMYSTERY

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ContentsContentsDark MatterDark Matter

Why do we need it?Why do we need it?How much is there?How much is there?What might it be?What might it be?How do we look for it?How do we look for it?

A journey through cosmology, astrophysics, A journey through cosmology, astrophysics, particle physics (and the deep sea!) using some particle physics (and the deep sea!) using some of the largest and smallest masses and distance of the largest and smallest masses and distance scales known (e.g. superscales known (e.g. super--clusters of galaxies to clusters of galaxies to neutrinos) to understand one of the great neutrinos) to understand one of the great mysteries of science mysteries of science -- the origin of dark matterthe origin of dark matter

Why do we need dark matter?Why do we need dark matter?

Measurements of the rotation curves of our own galaxy and Measurements of the rotation curves of our own galaxy and many other galaxies tell us that the luminous matter alone many other galaxies tell us that the luminous matter alone is is not sufficientnot sufficient to explain the observed dynamicsto explain the observed dynamics

M31 Image: Jason Ware

Andromeda Galaxy M31

NewtonianMechanics predicts the

rotational velocity of stars around the galactic centre should decrease

with increasing distance from galactic

centre

Why do we need dark matter?Why do we need dark matter?

Gravitational Gravitational lensinglensing, predicted by Einstein, predicted by EinsteinHere multiple images of a background object can be seen in the gHere multiple images of a background object can be seen in the galaxy alaxy cluster CL0024+1654cluster CL0024+1654Light from this object is bent and focused by the matter in the Light from this object is bent and focused by the matter in the clusterclusterAnalysis of these distortions enable the matter profile of the cAnalysis of these distortions enable the matter profile of the cluster to luster to tbe tbe mappedmapped

Types of dark matter: Hot or Cold?Types of dark matter: Hot or Cold?Hot dark matter or Cold dark matter?Hot dark matter or Cold dark matter?

Hot = fast moving or relativisticHot = fast moving or relativisticCold = slow movingCold = slow moving

Hot dark matter would be some particle left over from the Hot dark matter would be some particle left over from the Big Bang that is light, fast moving and weakly interacting. Big Bang that is light, fast moving and weakly interacting. Suitable candidates include a massive neutrino. A Suitable candidates include a massive neutrino. A neutrino with a mass of just 92eV (1/5000 x neutrino with a mass of just 92eV (1/5000 x MMelectronelectron!) !) could account for all the missing mass in the Universe!could account for all the missing mass in the Universe!Cold dark matter (CDM) would be a slow moving, possibly Cold dark matter (CDM) would be a slow moving, possibly massive particlemassive particleHow can we tell them apart?How can we tell them apart?Look at large scale structure in the Universe. Look at large scale structure in the Universe.

Types of dark matter: Hot or Cold?Types of dark matter: Hot or Cold?Modelling of large scale structure of galaxies in a CDM dominated Universe. Galaxies form earlier. Less definition of galactic superclusters.

Modelling of large scale structure in an HDM dominated Universe. Galaxies form earlier giving more time for large scale structure to form

Types of dark matter: (non)baryonicTypes of dark matter: (non)baryonicBaryons, like protons and Baryons, like protons and neutrons could contribute to the neutrons could contribute to the dark matter problem in the form dark matter problem in the form of nonof non--luminous objects.luminous objects.The amount of baryonic matter The amount of baryonic matter in the Universe is related to in the Universe is related to abundances of elements such abundances of elements such as as 22H, H, 33He, He, 44He and He and 77Li Li produced at the start of the produced at the start of the Universe.Universe.Current measurements indicate Current measurements indicate only a small fraction of the only a small fraction of the matter in the Universe is matter in the Universe is baryonic.baryonic.So, there is a more exotic, nonSo, there is a more exotic, non--baryonic component baryonic component

Summary so far Summary so far ……A lot of dark matter is needed to explain astrophysical A lot of dark matter is needed to explain astrophysical observationsobservationsLarge scale structure prefers a cold (nonLarge scale structure prefers a cold (non--relativistic) relativistic) dominated Universedominated UniverseSome (small amounts) of hot dark matter is allowedSome (small amounts) of hot dark matter is allowedDark matter appears to be predominantly nonDark matter appears to be predominantly non--baryonicbaryonicCan we determine exactly how much dark matter there Can we determine exactly how much dark matter there is?is?

Yes! Recent results from looking at the Cosmic Yes! Recent results from looking at the Cosmic Microwave Background (CMB) and type 1a supernovae Microwave Background (CMB) and type 1a supernovae combine to give stringent limits on the different combine to give stringent limits on the different components to the overall matter density of the Universecomponents to the overall matter density of the Universe

How much dark matter is there?How much dark matter is there?

SCPSCPType Type Ia Ia supernova supernova -- death throes of a dying stardeath throes of a dying starBriefly luminous as a complete galaxy! Huge energy releaseBriefly luminous as a complete galaxy! Huge energy releaseStar always explodes with Star always explodes with samesame brightness with brightness with samesame time profile time profile (light curve)(light curve)Acts as a standard candleActs as a standard candle

How much dark matter is there?How much dark matter is there?WMAPWMAP

SatelliteSatellite--borne experiment to map the CMB borne experiment to map the CMB (photons from the early Universe that last (photons from the early Universe that last scattered when the Universe had cooled scattered when the Universe had cooled sufficiently, 300,000 years after the Big sufficiently, 300,000 years after the Big Bang)Bang)

Anisotropies in the CMB measured at the 10-5

level

This is essentially a picture of the Universe 300,000 years ago. The minute temperature variations observed (10’s of micro-Kelvin) are very sensitive to the structure of the Universe at that time

How much dark matter is there?How much dark matter is there?

Understanding how CMB data can determine cosmological Understanding how CMB data can determine cosmological parameters. From Max parameters. From Max TegmarkTegmark’’s s CMB website.CMB website.

QuickTime™ and a GIF decompressor are needed to see this picture.

(top) CMB and (bottom) galaxy power spectra

CMB acoustic peaks change due to a complicated relationship between dark matter and number of baryons

These two experiments have These two experiments have made some significant made some significant conclusions to cosmologyconclusions to cosmology

Universe is acceleratingUniverse is acceleratingUniverse is flat (zero curvature)Universe is flat (zero curvature)Baryon density measured and Baryon density measured and agrees with BBNSagrees with BBNS

For the matter density of the For the matter density of the Universe combining results Universe combining results from the two experiments from the two experiments provides strong constraintsprovides strong constraints

How much dark matter is there?How much dark matter is there?

How much dark matter is there?How much dark matter is there?So our current picture of the Universe looks So our current picture of the Universe looks something like this:something like this: free H and He

~3%

stars~0.5%

dark matter23%dark energy

73%

neutrinos~0.5%

heavyelements>>1%

What might this dark matter be?What might this dark matter be?Summary:Summary:

NonNon--baryonicbaryonicMassiveMassiveWeakly interactingWeakly interacting

WIMP (Weakly Interacting Massive Particle)WIMP (Weakly Interacting Massive Particle)

What are the candidates (suspects)?What are the candidates (suspects)?AxionsAxions

((super light (Msuper light (Maa ≥≥ 1010--1515GeV) particles that couple to GeV) particles that couple to photonsphotons

Neutralinos Neutralinos -- see next slidessee next slidesSuperheavy Superheavy dark matterdark matter

Particles with M Particles with M ≥≥ 10101414±±55GeV, relics of the early Universe GeV, relics of the early Universe --may explain UHECRmay explain UHECR

What might this dark matter be?What might this dark matter be?SUSY is motivated by SUSY is motivated by some underlying some underlying problems with the problems with the standard model, unifies standard model, unifies couplings at high couplings at high energyenergySupersymmetry Supersymmetry requires there to be an requires there to be an LSP LSP -- a lightest a lightest supersymmetric supersymmetric particle particle that is stable, massive, that is stable, massive, and weakly interacting and weakly interacting (sounds familiar!)(sounds familiar!)A good candidate for the LSP is the A good candidate for the LSP is the neutralino neutralino which is also which is also electrically neutral electrically neutral If the If the neutralino neutralino (c) has mass less than ~ 1 (c) has mass less than ~ 1 TeV TeV its its ““relic relic abundanceabundance”” can account for the CDM deficit required in the can account for the CDM deficit required in the UniverseUniverse

How can we look for dark matter?How can we look for dark matter?Electrically neutral :Electrically neutral :--((Weakly interacting :Weakly interacting :--((Massive! :Massive! :--))Moving with high (although not relativistic) velocityMoving with high (although not relativistic) velocityLook for effect in matterLook for effect in matter

Scintillators give off a flash of light after nuclear recoil, e.g: NaI, CsI

Ionization (free electrons, ions) can be drifted in a electric field and detected on an electrode

Phonons are produced in e.g: a crystal lattice and can be detected via a small temperature increase (requires

i )

How can we look for dark matter?How can we look for dark matter?DIRECT DETECTION TECHNIQUESDIRECT DETECTION TECHNIQUES

Require as much target mass as possibleRequire as much target mass as possibleNeed to be as insensitive as possible to sources Need to be as insensitive as possible to sources of background events such asof background events such as

Cosmic rays Cosmic rays ----> go underground> go undergroundNatural Radioactivity Natural Radioactivity ----> shield the detectors> shield the detectorsNeutrons (from cosmic rays) Neutrons (from cosmic rays)

Plymouth

London

Birmingham

Liverpool

Newcastle

Edinburgh

Inverness

Belfast

Dublin

Redcar

Hartlepool

Peterlee

Middlesbrough

Billingham

on Aycliffe

Stockton

arlington

How can we look for dark matter?How can we look for dark matter?The ZEPLIN projectThe ZEPLIN projectUses Liquid Xenon as a Uses Liquid Xenon as a targettargetTarget sits inside a Target sits inside a ““Compton vetoCompton veto”” -- a tank a tank of mineral oil that helps of mineral oil that helps to discriminate against to discriminate against background gamma ray background gamma ray eventsevents

Visualisation of events seen in the detector. “Arms” correspond to 3 PMTs

How can we look for dark matter?How can we look for dark matter?χ

ν

In the Sun: over time theneutralino population builds up at the core to an equilibrium value

Can also look for decay products other than neutrinos (positrons, photons, etc.)

•• WIMPs WIMPs ((NeutralinosNeutralinos) become ) become gravitationally trapped in the gravitationally trapped in the cores of massive astrophysical cores of massive astrophysical objectsobjects

•• Neutralinos Neutralinos are their own antiare their own anti--particle (particle (Majorana Majorana particles)particles)

•• Neutralinos Neutralinos selfself--annihilate into annihilate into fermions or combinations of fermions or combinations of gauge and Higgs bosonsgauge and Higgs bosons

•• Subsequent decays of c,b and t Subsequent decays of c,b and t quarks, quarks, �� leptons and Z, W and leptons and Z, W and Higgs bosons can produce a Higgs bosons can produce a significant flux of highsignificant flux of high--energy energy neutrinos.neutrinos.

How can we look for dark matter?How can we look for dark matter?

•Another possibility:•There is significant evidence for a 3.0 x106 Solar mass black hole at the centre of the galaxy•Some speculation that we will observe enhancements of neutrinos from neutralino annihilations•Different BH formation models to be investigated

Galactic Centre

Now excluded by other meas.

How can we look for dark matter?How can we look for dark matter?

Energy spectrum of neutrinos (and hence Energy spectrum of neutrinos (and hence muons muons seen in a seen in a neutrino telescope) is related to neutrino telescope) is related to neutralino neutralino massmass

A simulated ANTARES

event showing the

muon trajectory,Cerenkov light rays and PMT

hits

A simulated A simulated ANTARES ANTARES

event event showing the showing the

muon muon trajectory,trajectory,Cerenkov Cerenkov light rays light rays and PMT and PMT

hitshits

QuickTime™ and a GIF decompressor are needed to see this picture.

ANTARES siteANTARES site

Mediterranean SeaMediterranean Sea2450m below sea level2450m below sea level

30km off the coast of Toulon in Southern France - close enough to perform return trip and deployment in 1 day

Shore Station

Shore station infrastructureShore station infrastructure

Land Cable (Fibre optic)

Detector Assembly HallFoseley Marine

Power HutLes Sablettes

La La Seyne sur MerSeyne sur Mer

Chambre de test

Zone d’intégration

Stockage

Salle de contrôle

Préparation

Shore Station Inst. Michel Pacha

Submarine cable(Fibre optic + power )

ANTARES Detector DesignANTARES Detector Design

450m

14.5m

Anchoring Weight

BuoyancyModule

~60m

3 PMTs per storey25 storeys per string

EO cable to shore

JunctionBox

ANTARES optical modulesANTARES optical modules

1010”” photomultiplier (photomultiplier (HamamatsuHamamatsu))

Active PMT base (ISEG)Active PMT base (ISEG)

LED pulserLED pulser Optical gelOptical gel

Glass sphere (Nautilus)Glass sphere (Nautilus)

Mu Mu metal magnetic shieldmetal magnetic shield

Large area Large area photocathodephotocathode

ANTARES sky coverageANTARES sky coverageANTARES has 3.5ANTARES has 3.5ππ sr sr coverage coverage

ANTARESANTARES--AMANDA AMANDA overlap is 0.5overlap is 0.5ππ sr sr at any at any one time, 1.one time, 1.5π5π sr sr in total in total --good for systematic good for systematic studiesstudies

ANTARES ANTARES ““seessees”” the the galactic centre more than galactic centre more than 2/3rds of the time2/3rds of the time

Need neutrino telescopes Need neutrino telescopes in both hemispheresin both hemispheres

ANTARES (430 N)

AMANDA (South Pole)

Never seen

PSR B1706-44

RXJ 1713.7-39

Mkn 421Mkn 501

PKS 2155-30

SN1006

VELA

CasA1ES2344+514

CRAB

ANTARES timelineANTARES timelineCollaboration formedCollaboration formed

EO Cable EO Cable deployed and deployed and testedtested

Junction Box, Sector Junction Box, Sector Line deploymentLine deployment

Deployment of Deployment of lines 1 to 12lines 1 to 12

0.1km0.1km22

detectordetectorcompletecomplete

Site evaluation programme Site evaluation programme to determine suitability of to determine suitability of chosen sitechosen site

““DemonstratorDemonstrator””line deployment line deployment and operationand operation

MIL deploymentMIL deploymentSubmarine connectionSubmarine connection

Mass productionMass productionAssemblyAssembly

Recent Progress: Junction BoxRecent Progress: Junction Box

Recent Progress: Prototype StringRecent Progress: Prototype String

Recent Progress: Undersea ConnectionRecent Progress: Undersea Connection

Sensitivities to dark matterSensitivities to dark matterDIRECT DETECTION EXPERIMENTSDIRECT DETECTION EXPERIMENTS

Sensitive to the WIMPSensitive to the WIMP--nucleon cross sectionnucleon cross sectionCan be spinCan be spin--dependent or spindependent or spin--independent according to the independent according to the choice of targetchoice of targetTraditionally presented as a curve in crossTraditionally presented as a curve in cross--section section vsvs. WIMP mass . WIMP mass parameter spaceparameter space

INDIRECT DETECTION EXPERIMENTSINDIRECT DETECTION EXPERIMENTSSensitive to a flux of secondary particles (in the case of ANTARSensitive to a flux of secondary particles (in the case of ANTARES ES this is neutrinos, but could be other type)this is neutrinos, but could be other type)Presented as a curve in flux Presented as a curve in flux vsvs. . neutralino neutralino massmass

COMPARISON DIFFICULT (NOT IMPOSSIBLE)COMPARISON DIFFICULT (NOT IMPOSSIBLE)IN BOTH CASES MAY SUPERIMPOSE SUSY MODEL IN BOTH CASES MAY SUPERIMPOSE SUSY MODEL PREDICTIONSPREDICTIONS

Sensitivities to dark matterSensitivities to dark matterCurrent limits from directdetection experiments

(prelim.)

Sensitivities to dark matterSensitivities to dark matter

ANTARESANTARES muon muon flux limitflux limit compared compared with predictions with predictions from a scan over from a scan over mSUGRAmSUGRA(cMSSM) (cMSSM) parameter spaceparameter spaceDots are colourDots are colour--coded according to coded according to the the relic densityrelic densitypredicted by the predicted by the modelmodel

ANTARES ANTARES sensitivity to a sensitivity to a muon muon flux from flux from neutralino neutralino decay in the decay in the SunSunPoints Points correspond to correspond to individual individual SUSY models SUSY models generated generated within a within a constrained constrained SUSY SUSY frameworkframework

Sensitivities to dark matterSensitivities to dark matter

Same constrained Same constrained SUSY modelsSUSY modelsComparison of Comparison of direct and indirect direct and indirect detection detection sensitivitiessensitivitiesObvious Obvious complementarity complementarity between the two between the two methodsmethods

Sensitivity to dark matterSensitivity to dark matterRange of Range of parameter parameter space that is space that is relevant when relevant when relaxing relaxing requirements requirements imposed by imposed by constrained constrained MSSMMSSMPurple region Purple region is already is already ruled out by ruled out by ZEPLIN and ZEPLIN and EDELWEISSEDELWEISS

ANTARES, 3yr

Roszkowski et. al

ConclusionConclusion~25% of our Universe is in the form of ~25% of our Universe is in the form of ““Dark Dark MatterMatter””Thanks to numerous clues from LSS, WMAP, Thanks to numerous clues from LSS, WMAP, SCP, etc. we have a SCP, etc. we have a ““prime suspectprime suspect”” in the form of in the form of the the neutralinoneutralinoThere is a worldThere is a world--wide search for this suspect, huge wide search for this suspect, huge international collaboration, very thorough search international collaboration, very thorough search includes deep mines, bottom of the seaincludes deep mines, bottom of the seaSo far our suspect has eluded us So far our suspect has eluded us butbut our methods our methods and techniques are getting more powerful and and techniques are getting more powerful and there is a hope that the there is a hope that the neutralinoneutralino will find it difficult will find it difficult to hide for much longerto hide for much longerANTARES is wellANTARES is well--placed to play an important role placed to play an important role in this particular WHODUNNIT!in this particular WHODUNNIT!

Sensitivities to dark matterSensitivities to dark matter

Important question: Important question: how does this how does this sensitivity compare sensitivity compare to that of to that of direct direct detectiondetectionexperiments?experiments?Here we use the Here we use the same same mSUGRA mSUGRA modelsmodels as in the as in the previous plotsprevious plotsEDELWEISS IIEDELWEISS II limit limit are on a are on a similar timesimilar time--scalescale (probably a (probably a little longer) than little longer) than ANTARES 3 yearsANTARES 3 yearslimitslimits

For the same For the same SUSY models in SUSY models in the previous plot the previous plot sensitivity to sensitivity to scalar crossscalar cross--section from section from established and established and proposed proposed bolometric direct bolometric direct detection detection experimentsexperiments