Study Of The J^PC=1^-- Charmonium States Decaying Into B（?） And D（?） At BESⅢ

Since the first member of charmonium family J/ψwas discovered experimentally in 1974,many charmonium states with J^PC=1^--were subsequently discovered,such asψ（2S）,ψ（3S）,ψ（4S）,ψ（1D）,ψ（2D）,etc.,where J/ψandψ（2S）are the vector ground state and first radial excited state,respectively.At present,the study of the exclusive J/ψandψ（2S）decays into baryon anti-baryon pairs（BˉB）was poor in experiment.Although the corresponding calculation of these exclusive processes were performed by QCD theoretical model,the naive prediction suffers from the apparent approximations.At the same time,according to the previous measurement of R（s）=_{σ（e+e-→μ+μ-）}^{σ（e+e-→hadron）}and combined with the theoretical prediction,it implies a rich structure or new resonance states above the DˉD mass threshold that have not been completely confirmed yet.Therefore,the study of the exclusive J/ψandψ（2S）decays into baryon anti-baryon pairs and e⁺e^-→DˉD cross section in experiment will help us test and understand the validity of the corresponding physical models and the nature of cˉc states above DˉD threshold.In 2009 and 2012,the BESIII detector has collected about 1310 million J/ψ,448millionψ（2S）and 5 fb^-1XYZ data sample,which can provide the unique opportunity for the studies of the J/ψandψ（2S）decaying into the baryon anti-baryon pairs and measurement of the e⁺e^-→DˉD（D=D⁺,D⁰）cross section in the J^PC=1^--charmonium（-like）states decay.In this dissertation,based on the single reconstruction method,we study the exclusive decays of J/ψandψ（2S）into the baryon anti-baryon pairs and the exclusive process of e⁺e^-→DˉD in detail.For the former,we measured the branching fraction and angular distribution parameterαfor each exclusive process of J/ψandψ（2S）→BˉB（B∈Ξ,Σ（1385）,Ξ（1530）^-）,in which the measured results are not only in good agreement with the previous measurements within the error,but also presents the most accurate measurements in the world.Moreover,using the measured branching fractions for each exclusive process,the ratio_{Br（J/ψ）^{Br（ψ（2S）→B）→BˉBˉB}}for testing“12%rule”is calculated,and it deviates from 12%,which means that“12%rule”is violated.These results provide the rich experimental evidences for understanding the decay mechanism of J/ψandψ（2S）and exploring the law of the hadron structure related to the non-perturbative property of the strong interaction.For the latter,we measure 17 Born cross sections for the exclusive process of e⁺e^-annihilation into DˉD in the center-of-mass energy from 3.9 GeV to 4.6GeV for the first time,in which the trend of line shape is basically consistent with the observed cross section from other experiments and the theoretical prediction of potential model.These results also provide the rich experimental evidences for understanding the nature above the DˉD mass threshold.