Indirect Search for Neutralino Dark Matter with Hi

arXiv:hep-ph/0105182v117May2001MADPH-00-1195OKHEP-00-08hep-ph/0105182May2001IndirectSearchforNeutralinoDarkMatterwithHighEnergyNeutrinosV.Bargera,FrancisHalzena,DanHooperaandChungKaobaDepartmentofPhysics,UniversityofWisconsin,Madison,WI53706bDepartmentofPhysicsandAstronomy,UniversityofOklahoma,Norman,OK73019AbstractWeinvestigatetheprospectsofindirectsearchesforsupersymmetricneu-tralinodarkmatter.RelicneutralinosgravitationallyaccumulateintheSunandtheirannihilationsproducehighenergyneutrinos.MuonneutrinosofthisorigincanbeseeninlargedetectorslikeAMANDA,IceCubeandANTARES.Weevaluatetherelicdensityandthedetectionrateinseveralmodels—theminimalsupersymmetricmodel,minimalsupergravity,andsupergravitywithnon-universalHiggsbosonmassesatthegrandunificationscale.Wemakere-alisticestimatesfortheindirectdetectionratesincludingeffectsofthemuondetectionthreshold,quarkhadronization,andsolarabsorption.Wefindgoodprospectsfordetectionofneutralinoswithmassabove200GeV.TypesetusingREVTEX1I.INTRODUCTIONAveragematterandenergydensitiesintheUniverse(ρi)arecommonlydescribedintermsofdensityparameters(Ωi=ρi/ρc),whereρc=3H20/(8πGN)≃1.88×10−29h2g/cm3,(1)isthecriticaldensitytoclosetheUniverse,h=H0/(100kmsec−1Mpc−1),H0istheHubbleconstant,andGNisNewton’sgravitationalconstant.RecentmeasurementsoftheHubbleconstantareconvergingtoh≃0.6−0.7[1–3].StudiesofclustersofgalaxiesandlargescalestructureindicatethatthematterdensityshouldbeatleastΩM∼0.2[4].ThematterdensityinferredfromobservationsofclusterX-ray[5],supernovae[6],andthecosmicmicrowavebackgroundradiation(CMB)anisotropydata[7–9]isΩM≃0.3−0.4.ThebaryondensityinferredfromBig-BangNucleosynthesisisΩbh2≃0.020±0.002[10]whichisingoodagreementwiththevalueobtainedfromrecentanalysesoftheCMBpowerspectrum[7,9].TheluminousmatterintheUniversehasaverysmallrelativedensityΩL∼0.01[11].Therefore,theevidenceforsubstantialdarkmatteriscompelling.Moreover,thedominantcomponentmustbecolddarkmattertobeconsistentwithlargescalestructure[12].Themostattractivecolddarkmattercandidatesarestableweaklyinteractingmassparticles(WIMPs)producedintheearlyUniverse.Inouranalysis,wetakeΩχ=ΩM−ΩbtobetheWIMPdensityandconservativelyconsider0.05∼Ωχh2∼0.3.(2)asthecosmologicallyinterestingregionforthecolddarkmatterdensity.IntheearlyUniverse,thetemperature(T)wasmuchhigherthantheWIMPmass(mχ)andWIMPsexistedabundantlyinthermalequilibriumwithWIMPannihilationintolighterparticlesbalancedbypairproduction.WhentheUniversecooledandthetemperaturefellbelowmχ,theWIMPdensitybecamesuppressedbytheBoltzmannfactorexp(−mχ/T).AsaresultoftheexpansionoftheUniverse,WIMPsdroppedoutofequilibriumwithotherparticlesatsomepoint,leavingarelicabundance.Fromsimpledimensionalanalysis,theWIMPannihilationcrosssectionisaboutσ∼α2/m2χ,(3)andtheirrelativedensityisΩχh2=mχnχ/ρc≃(3×10−27cm3/s)/σv∼(3×10−27cm3/s)(m2χ/α2),(4)whereαisthefine-structureconstant.ForaWIMPmassoftheorderoftheweakbosonmass,mχ∼mW,theWIMPdensityisΩχ∼1.Thus,acosmologicallyinterestingΩχisnaturalintheorieswithaweakscaleWIMPmass.Insupersymmetric(SUSY)theorieswithaconservedR-parity1,thelightestSUSYparti-cle(LSP)isstableandisthusanattractiveWIMPcandidate[14–16].Mostcommonly,the1R=+1forparticlesintheStandardModelaswellasHiggsbosonsandR=−1fortheirsuperpartners.2LSPisthelightestneutralinowhichisasuperpositionofthesupersymmetricpartnersofthephoton,theZbosonandtheneutralHiggsbosons.Thegauginoandhiggsinocompositionoftheneutralinoisanimportantfactorintheneutralinoannihilationcrosssection.Iftheneutralinosaremoregaugino-like,theyannihilatemostlyintob¯bandτ¯τ;iftheneutralinosarehiggsino-like,mostofthemannihilateintogaugebosonsandt¯t.WIMPsinthehaloofourgalaxyloseenergywhentheypassthroughtheSunandscatterfromnuclei.WhentheirvelocitiesfallbelowtheescapevelocityfromtheSun,theybecomegravitationallytrappedandaccumulate.AnnihilationsoftheseWIMPsareapotentialsourceofhighenergyneutrinosthatcanbedetectedviaCerenkovlightbylargeunder-iceorunder-waterphotomultiplierarraysinneutrinotelescopes,suchasAMANDA[17],IceCube[18]andANTARES[19].InthispaperweinvestigatetheprospectsofobservingmuonneutrinosproducedbyWIMPannihilationintheSun.Duetocosmicraybackgrounds,onlythesignalsfromthemuonneutrinosatorbelowthehorizontaldetectioncanbedetected.InSectionII,weestimatethegeneralexpectationsforneutrinosignalsfromWIMPannihilation,theeffectofthemuondetectionenergythreshold,andthebackgroundstothesignal.InSectionsIII,IVandV,weevaluatetheindirectdetectionratewithintheframeworkoftheminimalsupersymmetricmodel(MSSM),theminimalsupergravitymodel(mSUGRA),andsuper-gravityunifiedmodelswithnon-universalHiggsbosonmassesatthegrandunifiedscale,respectively.InSectionVIandVII,wesummarizetheprospectsofindirectsearchandourconclusionsaboutindirectdetectionofneutralinodarkmatterinlargeiceorwaterexperiments.II.INDIRECTDETECTIONOFWIMPSWhenourgalaxyformed,thecolddarkmatterWIMPswereclusteredwiththeluminousmatterandformedasignificantfractionofthegalacticmatterdensity[20,21]ρχ≃0.3−0.5GeV/cm3(5)asdeducedfromrotationcurves.ThedistributionofWIMPsinthegalactichaloisusuallyapproximatedasanisothermals