Dark Matter Anomalies

Theprevailingcosmologicalmodel,Lambda-CDM(ColdDarkMatter),suggeststhatordinarybaryonicmatter—theprotons,neutrons,andelectronscomprisingallvisiblestars,planets,andnebulae—accountsforashockinglymeager5%ofthetotalmass-energydensityoftheuniverse.Thevastmajorityofthecosmos'smassisattributedtoaninvisible,highlyelusivesubstanceknownasDarkMatter,representingroughly27%oftheuniversalbudget.Theprimaryempiricalevidencenecessitatingitsexistencestemsfromthesevereanomaliesobservedingalacticrotationcurves.AccordingtoclassicalNewtoniandynamicsandKepler'slaws,theorbitalvelocityofstarssituatedattheperipheryofaspiralgalaxyshoulddecreaseproportionallywiththeirdistancefromthedense,luminousgalacticcore,followingtheequationv=√(GM/r).However,rigorousspectroscopicobservationsutilizingtheDopplershiftofthe21-centimeterhydrogenemissionlineconclusivelydemonstratethatoutergalacticregionsrotateatinexplicablyhigh,constantvelocities.Withoutamassive,unseengravitationalanchor,theimmensecentrifugalforcesgeneratedbytheseflatrotationcurveswouldviolentlytearthegalaxyapart,flingingtheouterstarsintotheintergalacticvoid.Astrophysicistspostulatethatgalaxiesareentirelyenvelopedwithinmassive,diffusesphericalhalosofColdDarkMatter(CDM).TheleadingtheoreticalcandidatesforthisinvisiblemassareWeaklyInteractingMassiveParticles(WIMPs).WIMPsaretheorizedtopossessmassesrangingfrom10to1,000GeV/c^2butinteractwithordinarymatterexclusivelythroughgravityandtheweaknuclearforce,renderingthementirelytransparenttotheelectromagneticspectrum.Tocomplementthegruelingundergrounddirectdetectionefforts,astrophysicistsarealsoheavilyinvestinginindirectdetectionmethodologies,scanningthecosmosforthefaint,high-energysignaturesofDarkMatterannihilation.Theoreticalmodelssuggestthatintheincrediblydense,gravitationalheartsofgalaxies,twocollidingWIMPparticlescouldannihilateoneanother,instantlyconvertingtheirmassiverestmassintoahighlydetectableshowerofstandardmodelparticles,includinggammarays,positrons,andhigh-energyantiprotons.TheFermiGamma-raySpaceTelescopeconstantlyscansthecenteroftheMilkyWaygalaxysearchingforexactlythistypeofanomalousgamma-rayexcess.Alternatively,massiveparticleacceleratorsliketheLargeHadronCollider(LHC)areattemptingtoartificiallysynthesizeDarkMatterparticlesfromscratchbysmashingprotonstogetheratstaggeringenergiesapproaching13.6TeV,hopingtodeduceitsexistencemathematicallybycalculatingthemissingtransversemomentumcarriedawaybytheinvisibleparticle.