BESⅢ上X_2ccJ_→VV(V3dω，Φ)分支比测量

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1、ABSTRACTSinceBeijingElectronPositronCollider(BEPC)andBeijingSpectrometer(BES)werebuiltsuccessfullyin1989，nleyhavewellrun12yearsintheenergyregionof2GeV-5GeV,andobtainedimportantphysicsresults．inordortoacquirethelargerdatasampleandbetterdataquantity,weupgradethecollideranddetectorduring2003—2008．Th

2、enewcollideranddetectorarenamedasBEPCIIandBESIII．BEPCIIisacollider谢tlldoubleringsandoddbunches，itsdesignedluminosityis100timeslargerthanBEPCI’S．)ccJdecaysareregardedasallideallaboratorytotestQCDtheory．AtthelevelofleadingorderofQCDtheory,thehadronicdecaysof轴processviathec石quarksannihilationintotwo

3、gluons，thenfollwedbythehadronizationintolighthadrons．However,thetheoreticalcalculationfortheexclusivedecaysof)ccJintolighthadronsyieldssmallerbranchingfractionsthantheexperimentalmeasurements．Recently,thecontributionofthecoloroctetareproposed．SomecalculationofZcJdecaysintopseudoscalarpairandbaryo

4、nicpairareperformed．Itturnedoutthatthecoloroctetmechanismyieldacomparablebranchingfracions．Asforthedecaysof轴专W(v．vectormeson，J=O，2)，themeasuredbranchingfractionsarestillnotwellunderstoodinQCDtheory．Forexample，thedecayof‰．j-Yox0，¨(J=0，2)alesupprescdduotothehelicityselectionrule(HSR)．However,theBES

5、IImeasurementsshowthatthe轴hasalargerbranchingfractionstodecaysintothesefinalsmtes：Br(xcJ--)00)=(2．3i-0．7)x10-3andBr(Tca-)d脚)=(9．34-2．0)×10。．Forthedecaysof‰l专∞∞，)ccl专巾巾，theyaleexpectedtobehighlysuppressedduetotherequirmentsoftheidenticalparticlesymmetry．If(00and¨areregardedasidenticalparticles，the

6、nonlyD-waveoforbitalmomentumisallowedtooccurin‰Idecays．Forthedecaysof轴专∞巾，itisthedoublyOZIsuppresseddecay,andnomeasurementisavailableinpreviousexperiments．Inthisthesis，basedonthelargev(2S)datasampleincollectedatBESIII，wehaveobservedtheexplictsignalfromxcl专∞∞，巾巾and)Cc0专∞巾atfirsttime．Meanwhile，weco

7、nfirmthedecaymodesof轴．2专∞∞，¨whichhavebeenobservedinBESII．Thenumericalresultsarelistedbelow：IV◆Br(Xco--)toto)=(11．34-0．4(stat．净1．1(syst．))x10．4◆Br(x。l--)oo)=(6．2士o．3(stat．瑚．6(syst．))x10-4◆Br(yc．2-)oxo)=(8．4：tO．3(stat．净0