Deducing the nature of dark matter from direct and

arXiv:0808.3384v1[hep-ph]25Aug2008DeducingthenatureofdarkmatterfromdirectandindirectdetectionexperimentsintheabsenceofcollidersignaturesofnewphysicsMariaBeltranDepartmentofAstronomyandAstrophysics,TheUniversityofChicagoDanHooperTheoreticalAstrophysics,FermiNationalAcceleratorLaboratoryandDepartmentofAstronomyandAstrophysics,TheUniversityofChicagoEdwardW.KolbDepartmentofAstronomyandAstrophysics,EnricoFermiInstitute,andKavliInstituteforCosmologicalPhysics,TheUniversityofChicagoZosiaA.C.KrusbergDepartmentofPhysics,TheUniversityofChicagoDespitecompellingargumentsthatsignificantdiscoveriesofphysicsbeyondthestandardmodelarelikelytobemadeattheLargeHadronCollider,itremainspossiblethatthismachinewillmakenosuchdiscoveries,orwillmakenodiscoveriesdirectlyrelevanttothedarkmatterproblem.Inthisarticle,westudytheabilityofastrophysicalexperimentstodeducethenatureofdarkmatterinsuchascenario.Inmostdarkmatterstudies,therelicabundanceanddetectionprospectsareevaluatedwithinthecontextofsomespecificparticlephysicsmodelormodels(e.g.,supersymmetry).Here,weattempttodevelopamodel-independentapproachtowardthephenomenologyofweaklyinteractingmassiveparticlesintheabsenceofanydiscoveriesattheLargeHadronCollider.Inparticular,weconsidergenericfermionicorscalardarkmatterparticleswithavarietyofinteractionforms,andcalculatethecorrespondingconstraintsfromandsensitivityofdirectandindirectdetectionexperiments.Theresultsmayprovidesomeguidanceindisentanglinginformationfromfuturedirectandindirectdetectionexperiments.PACSnumbers:95.35.+d;95.30.Cq,95.85.Ry,95.55.Ka;FERMILAB-PUB-08-308-AI.INTRODUCTIONTheconsensusoftheastrophysicscommunityisthatalargefractionoftheuniverse’smassconsistsofnon-luminous,non-baryonicmaterial,knownasdarkmatter[1].Althoughthenatureofthissubstanceorsubstancesremainsunknown,weaklyinteractingmassiveparticles(WIMPs)representaparticularlyattractiveandwellmotivatedclassofpossibilities.AlthoughthemoststudiedWIMPcandidateisthelightestneutralino[2]insupersymmetricmodels,manyotherpossibilitieshavealsobeenproposed,includingKaluza-Kleinstatesinmodelswithuniversal[3]orwarped[4]extradimensions,stablestatesinLittleHiggstheories[5],andmanyothers.Ineachoftheabovementionedcases,manynewparticlespecies,inadditiontotheWIMPitself,areexpectedtoliewithinthediscoveryreachoftheLargeHadronCollider(LHC),makingthetaskofdeducingthenatureoftheWIMPimmeasurablysimpler.Insupersymmetry,forexample,gluinosandsquarksareexpectedtobeproducedprolifically.Bystudyingthecascadesproducedinthedecaysofsuchparticles,themassesofseveralsuperparticlemasses,includingthelightestneutralino,arelikelytobedetermined.Ifsquarks,gluinos,andotheradditionalsuperpartnersaretooheavytobeproduced,however,thelightestneutralinowillalsobeverydifficulttostudyattheLHC,evenifratherlightitself.Moregenerallyspeaking,intheabsenceofheavierparticleswithsharedquantumnumbers,WIMPswillnotbeeasilydetectedorstudiedattheLHC.Althoughanelectroweakscale,coldthermalrelicparticle,ifitexists,wouldalmostcertainlybeproducedattheLHC,identifyingandcharacterizingthenatureoftheWIMPsimplyfrommissingenergystudiesisadaunting,perhapsimpossible,task[6,7].AlthoughtheusuallistofprospectiveWIMPsmentionedabovecontainssomeveryattractiveandwell-motivatedcandidatesfordarkmatter,therearecertainlymanypossibleformsofdarkmatterthathavenotyetbeenconsidered.Asthefirstobservationsofparticledarkmattermightwellcomefromdirectand/orindirectdetectionexperiments,itispossiblethattheseresultsmaybemisinterpretedasaresultoftheoreticalbias,anticipatingdarkmattertohavethepropertiesofaneutralinoorotheroftenstudiedcandidates.Toavoidsuchconfusion,model-independentstudiesofdarkmatterphenomenologycanplayanimportantrole(forpreviousworkinthisdirection,seeRefs.[6,8,9]).Inthisarticle,ratherthanconsideraWIMPcandidatefromaspecifictheoreticalmodel,westudymodel-independentWIMPswithdifferentcombinationsofspinsandinteractionformswithstandardmodelparticles.These2interactionsarelimitedonlybytherequirementsofLorentzinvarianceandaconsequentWIMPabundanceconsis-tentwithcosmologicalobservations.Foreachspinandinteractionform,wethenevaluatetheconstraintsfromandprospectsfordirectandindirectdetectionofWIMPsincurrentandfutureexperiments.Althoughwewillbeforcedtoadoptsomeassumptionsinordertomaketheproblemsathandtractable,weattempttobeasgeneralaspossiblethroughoutourstudy.BeyondthestartingpointthatthedarkmatterisaWIMPintheformofasinglespeciesofacoldthermalrelic,weadoptonlytwoassumptions:1.WewillassumethatanynewparticlespeciesinadditiontotheWIMPhasamassmuchlargerthantheWIMP.2.WeassumethattheWIMPinteractionswithstandardmodelparticlesaredominatedbythoseofoneform(scalar,vector,etc.).AnimplicationofthefirstassumptionisthattheWIMP’sthermalabundanceisnotaffectedbyresonancesorcoannihilations.Atalaterstageofthispaper,wewilldiscusstheimpactofrelaxingtheseassumptions.Theremainderofthispaperisstructuredasfollows.InSec.IIweexplorethephenomenologyofagenericfermionicWIMP,includingthecalculationofitsannihilationcrosssectionandrelicabundance,elasticscatteringcrosssectionanddirectdetectionprospects,indirectd