New Ideas About Dark Maer MIT CTP 50web.mit.edu/~csuggs/www/ctp50slides/randall.pdf• Relave...
Transcript of New Ideas About Dark Maer MIT CTP 50web.mit.edu/~csuggs/www/ctp50slides/randall.pdf• Relave...
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NewIdeasAboutDarkMa2erMITCTP50
w/JakubSholtz,JamesUnwinw/Ma2Reece,JijiFan,AndreyKatz,Eric
Kramer,PrateekAgrawal,AlexandraShelestFrancisCyr-Racine
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AFewDecades….• 50yearsCTP
– 16.5yearsagoforme• Whathaschanged?
– Higgsfound• StronginteracUons,Supersymmetry,ExtraDimnotYET
– DarkMa2er• Increasinglystrongevidence• But
– MuchmoresensiUveWIMPsearches—nothing– Muchbe2erastronomicalstudies– Growingawarenessofotherpossiblemodels
– GravityWaves,BlackHoles• HybridInflaUonandBlackHoles• NuclearColloquium
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FOCUSTODAYONDARKMATTER—PERCHEDONDISCOVERY?
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MAKEUPOFUNIVERSE
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DarkMa2er
• Currentlyoutstandingcosmologicalmodel• But…leavescriUcalquesUonsunanswered– Natureofmostofthema2erandenergyintheUniverse
• Actuallynottoosurprising– Wehaveonlylimitedmeasuringtools– IfsomethinginteractsonlygravitaUonallyweliterallycan’tseeit
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Howdowe“see”(sofar)
• GalacUcrotaUoncurves• GalaxyclustersvirialvelociUes• GravitaUonallensing• Bulletclusterandothers• Supernovae• Cosmicmicrowavebackgroundstructure• ExistenceofgalaxiesinlifeUmeofUniverse• ExistenceofgalaxiesonscaleofMilkyWay
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• Thereisalotofevidence• Andit’sallconsistent• Basicallyhowanynewphenomenonorthingestablished
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WhatIsDarkMa=er?
• Someformofma2er– ButisitaparUcle?– Whatisitsmass?– WhatareinteracUons/charges– IsitjustonetypeofparUcle
• WeknowonlyofgravitaUonalinteracUons– NootherdiscernibleinteracUons(yet)
• Existencenotnecessarilysomysterious• Butmakeupofthema2ersUllis
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NatureDarkMa=er?• Wedon’tyetknow• WeknowgravitaUonalinteracUons
– ButnootherdiscernibleinteracUons(yet)• Existenceofdarkma2ernotnecessarilysomysterious• Buthowtofindwhatitis?
– Lookunderthelamppost– FindtheoreUcal,experimentalclues
• Whataretherightlampposts• WeneedtoconsiderallpossibiliUes
– Doesdarkma2erinteractas?– Doesitinteractdifferently?
• Nopromises• Opportunitytoconsidernewideas• Won’targuethatanysingleideahastobecorrect
– Infactweshouldneverhavedonethat• ButwillintroducepossibiliUes• AndconsiderpotenUalimplicaUons
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• Buthowtofindwhatitis?– Lookunderthelamppost– FindtheoreUcal,experimentalclues
• WeneedtoconsiderallpossibiliUes
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WIMPs
• UnUlrecentlymost“popular”candidate• WeaklyInteracUngMassiveParUcle• Merits– OccursinextensionsoftheStandardModel– TestablebecausenotonlygravitaUonalconnecUon
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WIMPS• Demerits– Notseen– BSMnotseen– Overhyped—otherpossibiliUes
• SearchestodatealwaysbasedonopUmisUcassumpUons– Darkma2erdoesinteractwithourma2eratsomelevel
– WIMP“standard”paradigm• ButSoFar– NodirectdetecUon– NoindirectdetecUon– LHChasn’tshownanysignofnewweakscalephysics
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Today
• Natureofdarkma2erremainsamystery– NosignofWIMPs– Sparsesignofnewweak-scalephysics
• PerhapssignsofdeviaUonsinsmall-scalestructure
• Somenewmodel-buildingideas• IfnotWIMPs,besttestsprobablyinvolvedetailedstructure
• CriUcaltofindimplicaUonsofmodels• Moregenerallyunderstandmodels,andhowtointegrateintoabiggerpicture
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OtherinteresUngpossibiliUes?
• Surprisingly,relaUvelyunexploredopUon:• InteracUngdarkma2er;chargedeven!• ThoughtUnlikely– EllipUcityofhalos– BulletClustertypeconstraints– Survivalofdwarfgalaxiesinhalos(lackofevaporaUon)
• Seemedtosignificantlyimpingeonparameterspace• ButmanyincorrectassumpUons,analyses
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Example:EllipUcityasfuncUonofradius
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Revisions:Notclearrighttarget
• RelaUveimportancevelocityanistropyversusthatinpotenUal?– Substructure,darkma2erstreams,asymmetricaccreUon
• Galaxyconstraintstrongerthangalaxyclusters– ButonlyNGC720measured
• Mergerhistoryalsoimportant–enoughUmeforellipUcitytobeerased?
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OurResult
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OtherCurves/Constraints
• BulletCluster—soweakwedon’tre-evaluate– ButnotepreciseboundisquesUonable– ExisUngboundcomesfromrequiringnomorethan30%ofdarkma2erlostinmerging
– Butwedon’tknowiniUaldarkma2ercontent• Orbaryontodarkma2erraUo
– Couldbethatconsiderablymoredarkma2ercanbelost
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Darkly-ChargedDarkMa2er
• Clearlyviable!!• Constraintsonmassconsiderablyweakerthanstated
• Andperhapsnotreliable– SimulaUonscanhelp
• ExciUngpossibilitythatdarkma2erhasitsownworldofinteracUons– Andthatconceivablywecandetectthem
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NewRegimeofInteracUonsDuality—andnewtests
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Anotherpossibility:onlyafracBoninteracts?
ParUallyInteracUngDarkMa2er:PIDM
• Ratherthanassumealldarkma2er• Assumeit’sonlyafracUon(maybelikebaryons?)• FracUonchangesallconstraints• ConvenUonalconstraintsevenweaker– IfonlyafracUoninteracUng,wouldn’tmakeenUre
thingisotropicveryefficiently– ClearlyBulletClusterokayifonlyafracUon–most
darkma2erwouldpassthrough– Anddwarfgalaxieswouldsurvive
• LotsofimportantimplicaUonsformeasurements
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ParUallyInteracUngDarkMa2er• Darkma2erwithitsownforce– Ratherthanassumealldarkma2er– Assumeit’sonlyafracUon–likebaryons…
• NonminimalassumpUon:whywouldwecare?• ImplicaUonsofasubdominantcomponent– CanberelevantforsignalsifitisdenserØ Canberelevantforstructure–likebaryons!
• Baryonsma2erbecauseformedinadensedisk– Perhapssameforcomponentofdarkma2er
• IntroducesdissipaUvemechanism– Canleadtodisks,pointlikesources
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DissipaUveFracUon
• Generatesstructure– Easiertodetect
• Significantconsequences– LeadstorethinkingofimplicaUonsofalmostalldarkma2er,astronomical,cosmologicalmeasurements
• Sincewedon’tknowwhatdarkma2eris– Shouldkeepanopenmind– Especiallyinlightofabundanceofastronomicaldata
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CouldinteracUngdarkma2ercool?IntoaDarkDisk?
• Togenerateadisk,coolingrequired• Baryonscoolbecauseelectronsradiateandinteract– TheytherebylowerkineUcenergyandvelocity– GetconfinedtosmallverUcalregion
• Diskbecauseangularmomentumconserved
• DarkdisktoorequiresameansofdissipaUngenergy• AssumeinteracUngcomponenthastherequisiteinteracUon
• SimplestopUondarkly-chargeddarkma2er
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SimpleDDDMModel:“DarkLight”• CouldbeU(1)oranonabeliangroup• U(1)D,αD• Twoma2erfields:aheavyfermionXandalightfermionC– For“coolant”aswewillsee
• qX=1,qC=-1• (Inprinciple,XandCcouldalsobescalars)• (inprinciplenonconfiningnonabeliangroup)• ThisinaddiUontodarkma2erparUclethatmakesupthehalo
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• WhenXfreezesoutwithweakscalemediators,couldhavehalftempofSMparUcles
• Inanycase,thermalabundanceofweakscaleparUclenaturallygivesrisetofracUonofdarkma2erabundance
• Probablyhaveboththermalandnonthermalcomponents
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Coolingtempdeterminesdiskheight• Andthereforedensityofnewcomponent
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Summaryofmodel
• Aheavycomponent– WasiniUallymoUvatedbyFermisignal
• Fordisktoform,requirelightcomponent– Can’tbethermal(densitywouldbetoolow)– Constraintondensityvsmass
• WiththesecondiUons,expectadarkdisk– Evennarrowerthanthegaseousdisk
• LotsofpotenUallyvisibleconsequences
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TradiUonal(WIMPy)Methods
• SmallerdirectdetecUon,smallvelocity– PossiblyothernoncanonicalpossibiliUes– Iffound,differentenergydistribuUon,Umedepce
• IndirectdetecUon– PossibleifmediaUonbetweenvisible,invisiblesectors
– Iffound,dfferentspaUaldistribuUon
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DisUncUveShapetoSignal
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AlsonewacousUcpeak
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BoundfromStructure• Recallboundfromshapesnotsobad
– Butboundfromfromma2eraccounUng– Anddetailedshapeofgalaxy
• GravitaUonalpotenUalmeasured– Bothinandoutofplaneofgalaxy– StarvelociUes
• Baryonicma2erindependentlyconstrained• Dominantcomponentofdarkma2erconstrained
– Extrapolatehalo• Totalconstraintonanynewformofma2er• Constrainsanynew(nonhalo)componentingalacUcplane
w/Kramer
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Hipparcos• FlynnHolberglookedatAandFtypestarsininnerporUonofgalaxy– BrightstarpopulaUon—enoughnearmidplane
• FromHipparcos,getvelocitymeasuredatmidplaneanddensityasfuncUonofverUcaldistance
• UsegalacUcmodelwithseveralisothermalcomponents
• AskedwhetherequilibriumdistribuUonfitpotenUalgeneratedbyMilkyWaydisk
EricKramer
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GeneralLesson
• RoleforparUclephysicsapproachinastronomy• “constraint”ondarkdiskcamefromfisngstandardcomponents– Turnsouterrorsonstandardcomponentsnotproperlyaccountedfor
– Hastobedoneself-consistently• Heredifferentcomponentsinfluenceeachotherthroughgravity
• Bigmessydatasets• TargeUngamodelhelps
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FitpotenUal/stardistribuUons
• Boltzmann/verUcalJeansequaUon• DistribuUonfallsoffmoreorlessexponenUallyoverascaleheight
• SolveJeansequaUon• UsePoisson’sequaUontointroducethedifferentsources/components
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ThiswillimprovedramaUcally
• GaiasurveymeasuringposiUonandvelocityofstarsinsolarneighborhood
• WillsignificantlyconstrainproperUesofourgalaxy
• InparUcular,newdiskcomponentwillgivemeasurablesignalifsurfacedensitysufficientlyheight
• Don’tknowhowmuchgasmeasurementswillimprovebuttheyshouldtoo
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ButanothertheoreUcallamppost?• Similarityofamountofenergyindarkma2erandordinaryma2er
• Maybema2eranddarkma2erareproducedinsimilarways?
• Excess“ma2er”over“anUma2er”
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SatellitesofAndromedaGalaxy• Abouthalfthesatellitesareapproximatelyina(bigplane)– 14kpcthick,400kpcwide
• Hardtoexplain• ProposedexplanaUon:Udalforceoftwomerginggalaxies
• Fineexceptofexcessivedarkma2ercontent• Tidalforcewouldusuallypulloutonlybaryonicma2erfromdisk
• Nottrueifdarkdisk
w/Scholtz
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MeteoroidPeriodicity?
• Meteoritedatabasegives21cratersbiggerthan20kmincircumferenceinlast250years
• Evidenceforabout35millionyearperiodicity• Evidencehowevergoesawaywhenlookelsewhereeffectincorporated
• Thiswillchangewithamodelandmeasuredpriors• Weassumeadarkdisktakeintoaccountconstraintsonmeasuredparameters,anddeterminewhetherlikelihoodraUoprefersmodeltoflatdistribuUon
• AndwhataposterioridistribuUonisfavored
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MoUonofSun;DensitySolarSystemEncounters
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IV:CouldmaybeevenexplaindinosaurexUncUon…
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• Clearlyabigprogram• Darkma2erchargedisclearlyapossibility• ManyimplicaUons• ButcansomeUmesbemoreelusiveorsubtlethananUcipated– IniUalcondiUondependence
• Wearebeginningtogettremendousdata• Let’sfindoutwhatitmeans