Study Of Some Charmoniumlike Decays At BESⅢ

After entering the 21st century,particle physics has developed rapidly in the study of Hadron Spectrum,especially in the study of charmonium states in decay final states,a series of new charmonium-like states that can’t be described by the traditional quark model have been found.The discovery of these exotic states not only poses new challenges to the quark model,but also provides a new opportunity to study strong interactions and test quantum chromodynamics（QCD）.The first charmonium-like state X（3872）,is found to be an isospin singlet with JPC=1++,the mass different between X（3872）and D0D*0 threshold which we denote as δ,δ is calculated to be（70±120）keV/c2.But the value of δ can’t tell us wether the X（3872）mass is above or below D0D*0 threshold,better knowledge of δ will be an important step towards a deeper understanding of the nature of the X（3872）.A completely new method to measure the δ value by measuring the X（3872）γ line shape,which is sensitive to the δ value,is proposed by a theoretical paper.Therefore,we can measure the X（3872）γ line shape through the process of e+e-→π0X（3872）γ.One such connection could be a transition Zc（4020）0→X（3872）γ in the scenario where the X（3872）is dominantly an S-wave D0D*0 0molecule and the Zc（4020）0 is an isotopic triplet of near-threshold S-wave D*D*resonances.Therefore,we can search for the process of Zc（4020）0→X（3872）γ through the process of e+e-→πX（3872）γ.Based on the data recorded with the BESⅢ detector in the range of 4.178<（?）<4.600 GeV,we studied the reaction of e+e-→π0X（3872）γ and searched for Zc（4020）0→X（3872）γ.In neither of the two processes are significant signals observed.Upper limits at the 90%confidence level（C.L.）on the cross sections multiplied by the branching fractions,the upper limits are not conflict with the theoretical expectation.Using the experimental results on the σ（e+e-→π0Zc（4020）0）· B（Zc（4020）0→（D*D*）0）,the ratio（B（Zc（4020）0→X（3872）γ）·B（X（3872）→π+π-J/ψ））/(B（Zc（4020）0→（D*D*）0）is determined to be less than 0.15%at the 90%C.L.The ratio does not contradict the prediction reported based on the molecular picture.The vector charmonium-like states is also called Y states.Experimentally,the Y states were mostly observed in states decaying into hidden or open charm states,but not into light hadron final states.Thus,searching for the Y states decaying into light hadron final states will improve our understanding of Y states.Based on the data recorded with the BESIII detector in the range of 3.773<（?）<4.701 GeV,we measured the Born cross sections of two light hadron channels e+e-→ωπ0 and e+e-→ωη.The power function of s-n can describe both line shapes well.No obvious ψ（4160）,ψ（4230）,ψ（4360）,ψ（4415）,ψ（4660）signals are found in the line shapes of e+e-→ωπ0 and e+e-→ωη,this suggests that the cross sections are too small for ωπ0 and ωπ decay modes.This provides input parameters for the theoretical model.