introduction to b physics

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1、CLNS00/1660January2000hep-ph/0001334IntroductiontoBPhysicsMatthiasNeubertNewmanLaboratoryofNuclearStudies,CornellUniversityIthaca,NewYork14853,USAAbstract:Theselecturesprovideanintroductiontovarioustopicsinheavy- avorphysics.Wereviewthetheoryandphenom

2、enologyofheavy-quarksymmetry,exclusiveweakdecaysofBmesons,inclusivede-cayrates,andsomerareBdecays.arXiv:hep-ph/0001334v131Jan2000LecturespresentedattheTriesteSummerSchoolinParticlePhysics(PartII)Trieste,Italy,21June{9July,1999INTRODUCTIONTOBPHYSICSMAT

3、THIASNEUBERTNewmanLaboratoryofNuclearStudiesCornellUniversity,Ithaca,NY14853,USATheselecturesprovideanintroductiontovarioustopicsinheavy- avorphysics.Wereviewthetheoryandphenomenologyofheavy-quarksymmetry,exclusiveweakdecaysofBmesons,inclusivedecayrat

4、es,andsomerareBdecays.1IntroductionTherichphenomenologyofweakdecayshasalwaysbeenasourceofinforma-tionaboutthenatureofelementaryparticleinteractions.Alongtimeago,-and-decayexperimentsrevealedthestructureoftheeective avor-changinginteractionsatlowmome

5、ntumtransfer.Today,weakdecaysofhadronscon-tainingheavyquarksareemployedfortestsoftheStandardModelandmea-surementsofitsparameters.Inparticular,theyoerthemostdirectwaytodeterminetheweakmixingangles,totesttheunitarityoftheCabibbo-Kobayashi-Maskawa(CKM)m

6、atrix,andtoexplorethephysicsofCPviolation.Hopefully,thiswillprovidesomehintsaboutNewPhysicsbeyondtheStan-dardModel.Ontheotherhand,hadronicweakdecaysalsoserveasaprobeofthatpartofstrong-interactionphenomenologywhichisleastunderstood:theconnementofquark

7、sandgluonsinsidehadrons.ThestructureofweakinteractionsintheStandardModelisrathersimple.Flavor-changingdecaysaremediatedbythecouplingofthechargedcurrentJtotheW-bosoneld:CCgyLCC=pJCCW+h.c.,(1)2where0101eLdLJ=(;;)@A+(u;c;t)V@sA(2)CCeL

8、LLLCKMLLbLcontainstheleft-handedleptonandquarkelds,and01VudVusVubVCKM=@VcdVcsVcbA(3)VtdVtsVtb1istheCKMmatrix.Atlowenergies,thecharged-currentinteractiongivesrisetolocalfour-fermioncouplingsoftheformpyLe=22GFJCCJCC;;(4)whereg2p2GF==1:166