High Energy Neutrinos From Superheavy Dark Matter

arXiv:hep-ph/0009017v13Sep2000FNAL-Pub-00/206-AIAS-SNS-AST-0035HighEnergyNeutrinosFromSuperheavyDarkMatterAnnihilationIvoneF.M.Albuquerque†SpaceScienceLaboratoryandAstronomyDepartment,UniversityofCalifornia,Berkeley,California94720LamHui‡InstituteforAdvancedStudy,SchoolofNaturalSciences,EinsteinDrive,Princeton,NewJersey08540,andDepartmentofPhysics,ColumbiaUniversity,538West120thStreet,NewYork,NewYork10027EdwardW.Kolb§NASA/FermilabAstrophysicsCenter,FermiNationalAcceleratorLaboratory,Batavia,Illinois60510-0500,andDepartmentofAstronomyandAstrophysics,EnricoFermiInstitute,TheUniversityofChicago,Chicago,Illinois60637-1433(Dated:August2000)AbstractSuperheavy(M1010GeV)particlesproducedduringinflationmaybethedarkmatter,inde-pendentoftheirinteractionstrength.Stronglyinteractingsuperheavyparticleswillbecapturedbythesun,andtheirannihilationinthecenterofthesunwillproduceafluxofenergeticneutrinosthatshouldbedetectablebyneutrinotelescopes.Dependingontheparticlemass,eventratesinacubic-kilometerdetectorrangefromseveralperhourtoseveralperyear.Thesignatureoftheprocessisapredominanceoftauneutrinos,witharelativelyflatenergyspectrumofeventsrangingfrom50GeVtomanyTeV,andwiththemeanenergyofdetectedtauneutrinosabout3TeV.PACSnumbers:98.80.Cq†Electronicmail:[e-mail]‡Electronicmail:[e-mail]§Electronicmail:[e-mail]ssumedthattheinteractionsofdarkmatterandordinarymatterareweak,atleastassmallasordinaryweakinteractions.Itisalsooftenassumedthatthedarkmatterisathermalrelicofthebigbang.Ifitisathermalrelicparticle,thenitsmassshouldbelessthan340TeV,theunitaritylimit[1].Theseconsiderationsleadtothepopularpictureforrelicdarkmatterofananelectricallyneutralparticle,withoutstronginteractions,andwithmasslessthanacoupleofhundredTeV.Inthispaperweexploreapathlesstraveled,andassumethatthedarkmatterisanonthermalrelic,itinteractsstronglywithnormalmatter,anditisverymassive.WeshowthatthecleansignatureofthispossibilityisadetectablefluxofenergeticneutrinosfromthesunIthaslongbeenappreciatedthatifthedarkmatterismassive,saylargerthanafewTeV,itwillbehaveeffectivelyasdissipationlessdarkmatterregardlessofwhetherithasstrongorelectromagneticinteractions[2,3].However,sincetheupperlimittothemassofathermalrelicisafewhundredTeV,thewindowforverymassivedarkmatterparticleswasthoughttobenotverywide.Therecentdevelopmentofscenariosfornonthermalproductionofdarkmatterhasopenedthewindowtothepossibilitythatthedarkmattermightbesupermassive,independentofitsinteractionstrength[4,5,6].Ofthemanypossibilitiesforproducingsupermassivedarkmatter,perhapsgravitationalproductionisthemostgeneral[4,5].Inthisscenario,darkmatterisproducedbyvacuumquantumfluctuationstowardtheendofinflation.Theresultingparticledensityisindependentoftheinteractionstrengthoftheparticle,whichleadstothepossibilitythatthedarkmattermaybeelectricallycharged,stronglyinteracting,weaklyinteracting,ormayhaveonlygravitationalinteractionswithnormalmatter.Aparticularlypromisingmassrangeforgravitationalproductionofdarkmatteristhemassscaleoftheinflaton,about1012GeVinchaoticinflationmodels.Iftheinflatonmassheraldsanewmassscale,thenitwouldbereasonabletoimaginethatthereareotherparticlesofsimilarmass.Furthermore,gravitationalproductionofparticleswithamasscomparabletotheinflatonmassnaturallyleavesbehindacosmologicallyinterestingdensityofdarkmattertoday[4].Theparticlecontentmayincludeexoticquarksorotherstronglyinteractingparticlesinthespectrumofnewparticles[7].Inthispaperwewillconsiderthecasethatthedarkmatterisstronglyinteractingandsupermassive,asimpzilla.Althoughourcalculationswillnotbesensitivetowhetherthesimpzillaiselectricallycharged,thereareargumentsthatsuggestthatthesimpzillamustbeneutral[8,9].ThepossibilitythatthedarkmattermaybeverymassiveandstronglyinteractingwasrecentlydiscussedbyFaraggi,Olive,andPospelov[10].Inthatpapertheyhaveanicediscussionoftheparticlephysicsmotivationsfortheexistenceofamassive,stable,stronglyinteractingparticle,andtheypointoutthatthesunandEarthmaybethesourceofhigh-energyneutrinosfromtheannihilationoftheparticles.Inthenextsectionwewillcalculatethetrappingrateandannihilationrateofsimpzillasinthesun(andEarth)asafunctionofthesimpzillamassandinteractioncrosssection.InSectionIIIwewilldiscusstheemergentspectrumofneutrinosfromsimpzillaannihilationinthecenterofthesun.InSectionIVwewillcalculatetheeventrateincubic-kilometerunderwaterorundericeneutrinodetectors.Finally,thelastsectioncontainsourconclusions.Apreviewofourmainconclusionisthatweexpectadetectablehigh-energysolarneutrinofluxformuchoftheparameterrangeofinterest.II.CAPTUREANDANNIHILATIONRATEBeforelaunchingintothedetailsofthecapture-ratecalculationitisusefultomakesomeextremelycrudeestimates.Thefirstestimateisforthenumberofsimpzillasthathitthesun.Assumingthesimpzillascomprisethelocaldarkmatterdensityof0.3GeVcm−3,thelocalnumberdensityofsimpzillasis3×10−13M−112cm−3,whereM12isthesimpzillamassinunitsof1012GeV.Assumingatypicalvelocityof240kms−1forthesimpzillas,thelocalfluxisapproximately6×10−7M−112cm−2s−1.Thesurfaceareaofthesunisabout6×1