Experimental Study Of Charmonium Transitions

Radiative transitions of ψ’ and hadronic transitions of XcJ are studied with the106M ψ’ events data sample, the hadronic process of e+e→π+π-hc are studied with827pb-1e+e-collision data at (?)=4.260GeV,545pb-1e+e-collision data at (?)=4.360GeV, and480pb-1ψ(4040) events data sample at (?)=4.009GeV; hadronic production of e+e-→π+π-hc is observed with data at4.260GeV and4.360GeV with an observation of a charged charmoniumlike state, the Zc(4020). All these data used were accumulated with the Beijing Spectrometer (BES) Ⅲ at the Beijing Electron Position Collider (BEPC) Ⅱ. The thesis includes the following two parts:?ψ’→γKKπππ(KKπππ represents KS0K±π+π+π-and K+K-π+π-π0), in-cluding the possible intermediate states are studied.-Precision measurement of the properties of ηc via ψ’→γηc, ηc→KKπππ. Using the model that incorporates interference between the signal reaction, ψ’→γηc, and a non-resonant radiative background to describe the line shape of the ηc, the mass and width of ηc are determined to be2984.3±0.6±0.6MeV/c2and32.0±1.2±1.0MeV, respectively, the first errors are statistical and the second ones are systematic. The results are the most precise measurement so far.-Search for the hadronic transition XcJ→ηcπ+π-via ηc→KS0K±π+and ηc→K+K-π0.No obvious ηc signals are observed in any of the three χcJ states in either ηc decay mode. At90%confidence level, the upper limits of B(χcJ→ηcπ+π-)are determined,which are: B(χc0→ηcπ+π-→(KS0±π+)π+π-)<0.07%, B(χc0→ηcπ+π-→(K+K-π0)π+π-)<0.41%, B(χc1→ηcπ+π-→(KS0±K±π+)π+π-)<0.32%, B(χc1→ηcπ+π-→(K+K-π0)π+π-)<0.44%, B(χc2→ηcπ+π-→(KS0K±π+)π+π-)<0.54%, B(χc2→ηcπ+π-→(K+K-π0)π+π-)<1.23%, The upper limit of BB(χc1→ηcπ+π-)is lower than the existing theoretical prediction by almost an order of magnitude.一Observation of B(χC1→KKπππ,here the χcJ originates from the E1transi-tion ψ→χcJ.The branching fractions of χcJ→KS0K±π+π+π-,χcJ→K+K-π+π-π0,χcJ→ωK+K-,and χcJ→φπ+π-π0are measured for the first time,which are: B(χc0→KS0K±π+π+π-)=(4.22±0.10±0.43)×10-3, B(χc0→K+K-π+π+π-)=(8.61±0.13±0.94)×10-3, B(χc0→ωK+K-)=(1.94±0.06±0.20)×10-3, B(χc0→φπ+π-π0)=(1.18±0.07±0.13)×10-3, B(χc1→KS0K±π+π+π-)=(7.52±0.11±0.79)×10-3, B(χc1→K+K-π+π+π-)=(11.46±0.12±1.29)×10-3, B(χc1→ωK+K-)=(0.78±0.04±0.08)×10-3, B(χc1→φπ+π-π0)=(0.75±0.06±0.08)×10-3, B(χc2→KS0K±π+π+π-)=(7.30±0.11±0.75)×10-3, B(χc2→K+K-π+π+π-)=(11.69±0.13±1.31)×10-3, B(χc2→ωK+K-)=(0.73±0.04±0.08)×10-3, B(χc2→φπ+π-π0)=(0.93±0.06±0.10)×10-3.Study of e+e-→π+π-hc via hc→γηc,ηc→Xi,here Xi={pp,π+π-pp,2(π+π-),2(K+K-),π+π-K+K-,3(π+π-),K+K-2(π+π-),KS0K±π+, KS0K±π+π+π-, K+K-π0, ppπ0,π+π-η, K+K-η,2(π+π-)η,π+π--π0π0,2(π+π-π0)}.The process e+e-→π+π-hc is first observed at4.260GeV and4.360GeV,the Born cross sections are measured to be(41.0±2.8±3.6±6.4)pb and(52.3±3.7±4.1±8.2)pb,respectively.In the process e+e-→π+π-hc at (?)=4.260GeV and4.360GeV,a charged chamoniumlike structure Zc(4020) in the mass spectrum of π±hc with a statistical significance of6.4σ is observed. Its mass and width are measured to be M=(4021.8±1.0±2.5)MeV/c2and r=(5.7±3.4±1.1)MeV,respectively.And its production ratio is measured to be and The Zc(4020)can be in- terpreted as an exotic hadron with at least four quarks.No obvious signals are observed in the summed invariant mass spectrum of γXi(16ηc decay modes) at ψ(4040),the upper limit of the cross section of e+e-→π+π-hc at(?)=4.009GeV is determined to be σ(e+e-→π+π-hc)<1.5pb at90%confidence level,corresponds to B(ψ(4040)→π+π-hc)<0.26×10-3.