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1、AnomalousgvaluesoftheelectronandmuonV.W.HughesPhysicsDepartment,YaleUniversity,NewHaven,Connecticut06520-8121T.KinoshitaNewmanLaboratory,CornellUniversity,Ithaca,NewYork14853-5001Recentadvancesintheoryandexperimentfortheanomalousmagneticmomentsoftheelectronandmuonar
2、ereviewed.Implicationsofthesedevelopmentsforfundamentalphysicsarediscussed.[S0034-6861(99)02402-2]I.INTRODUCTIONmeasurementsofam,willnotonlytestthestandardmodelfurtherbutmayopenupawindowintothestudyHistorically,thespinmagneticmomentoftheelec-ofentirelynewphysics.tro
3、nmeoritsgvaluegehasplayedacentralrolein(2)Themeasurementandtheoryofaehavebecomemodernphysics,datingfromitsdiscoveryinatomicop-soprecisethataegivesthemoststringenttestofQEDifticalspectroscopyanditssubsequentincorporationinaisknownprecisely.Unfortunately,noavailableai
4、stheDiractheoryoftheelectron,whichpredictedtheknownwithsuf®cientprecisiontoenablesuchatest.valuege52.Theexperimentaldiscoveryinatomicmi-Thismeans,however,thatthetheoryandmeasurementcrowavespectroscopythatgewaslargerthan2byamul-ofaetogetherwillleadtothemostpreciseval
5、ueofthetiplicativefactorofabout1partin103,ge®ne-structureconstantacurrentlyavailable.Compari-52.00238(10),togetherwiththediscoveryoftheLambsonofaderivedfromaewithotherhigh-precisionmea-shiftinhydrogen(S522S222P),ledtothedevel-1/21/2surementsofabasedoncondensed-matte
6、rphysics,opmentofmodernquantumelectrodynamicswithitsatomicphysics,andothermeansoffersanintriguingop-renormalizationprocedure.Thetheoryenablesustoportunitytointroduceaquantitativemeasureofthesuc-calculatetheseeffectspreciselyas®niteradiativecorrec-cessofquantumtheory
7、,whichisattherootofallphys-tions.Bynowtheexperimentalvalueofge22hasbeenicsdevelopedinthetwentiethcentury.Thistopicwillbemeasuredtoabout4ppb,andthetheoreticalvalue,discussedingreaterdetailinSec.VI.whichisexpressedasapowerseriesinthe®ne-structureconstanta,hasbeenevalu
8、atedtobetterthan1ppb,assumingthevalueofaisknown.Forthemuon,aswell,gmisgreaterthan2byamul-3II.ELECTRONg22EXPERIMENTStiplicativefactorofabou