【作者】 丁伟民；

【导师】 张学尧； 马海龙；

【作者基本信息】 山东大学 ， 粒子物理与原子核物理， 2014， 博士

【摘要】 DD阈上粲偶素的非DD衰变过程的研究,是τ-粲能区高能物理研究的重要课题之一。ψ(3770)是DD对产生闽上质量最低的粲偶素态,传统理论预期其衰变到DD过程的分支比大于98%。但是,实验结果显示ψ(3770)总截面和DD的产生截面存在明显(约15%)差异,而目前已知遍举衰变道的分之比之和不能解释此差异。在实验上寻找ψ(3770)的遍举轻强子衰变,有助于理解ψ(3770)的非DD衰变的起源。除此之外,对ψ(3770)和ψ(3686)遍举轻强子衰变的研究还可以为解释“ρ7r”疑难提供更多实验依据,并为理解B介子衰变末态再散射效应以及ψ(3770)共振态的衰变特性提供更多思路。BES Ⅲ实验在ψ(3770)峰上(√s=3.773GeV)采集了积分亮度约2.9f1D-1的数据。这是目前世界上最大的ψ(3770)数据样本。在本文中,我们利用此数据样本和√s=3.650GeV处采集的积分亮度约44.39pb-1的连续区数据,寻找了ψ(3770)→ψπ+π-,ψ(3770)→φπ0π0,ψ(3770)→φK+K-和ψ(3770)→φKSOKSO。在忽略ψ(3770)共振态衰变与e+e-电磁过程之间可能干涉的情况下测量得到的衰变分支比或分支比上限分别为其中对ψ(3770)→φπ0π0和ψ(3770)→φKSOKSO为实验上首次测量。对于ψ(3770)→φπ+π-衰变过程,我们首次观测到了显著性约3.1倍σ的信号,其在90%置信度下对应的衰变分支比上限为4.9×10-4。在本文中,我们还利用BES Ⅲ实验于2009年在ψ(3686)峰上(√s=3.686GeV)采集的(1.06±0.04)×108个ψ(3686)事例,精密测定了ψ(3686)衰变到φπ+π-,φπ0π0,φK+K-和φKSOKSO的衰变分支比为其中,对ψ(3686)→ψπ0π0和φKSOKSO分支比的测定为国际首次测量。本论文测得的ψ(3686)→φπ+π-和φK+K-分支比与《粒子数据手册》给出的世界平均值在误差范围内一致,但精度更高。本论文的研究结果,为理解ψ(3770)的非DD衰变之谜,及ψ(3686)衰变中的“ρπ”疑难提供了重要实验信息。更多还原

【Abstract】 The research on non-DD decay of charmonium states above DD threshold is an important topic in τ-charm physics. Ψ(3770) is the first charmonium state above DD threshold, and the studies of its properties are still on going. In traditional quarkonium potential theory,Ψ(3770) decays dominantly to DD with the branching fraction more than98%. But this prediction has conflicts with the experiment measurements. Measurements of the total Ψ(3770) production cross section and the DD cross section indicate that Ψ(3770) may have larger branching fraction (about15%) to decay into non-DD final states. Charmless decays of the Ψ(3770) and Ψ(3686) can shed light on S-D mixing,"ρπ" puzzle, the discrepancy between the total and the DD cross section at the Ψ(3770), and rescattering effects in B meson decays.BES Ⅲ experiment has collected a big data sample on Ψ(3770) resonance (√(S)=3-773GeV) with integrated luminosity about2.917fb-1, which is the largest data sample in statistic in the world. Using this data sample and the continuum data taken at√s=3.65GeV, we have searched for some non-DD processes of Ψ(3770)→light hadrons including Φ. Ignoring the possible inter-ference between the Ψ(3770) decay and the e+e-QED production, we measured the branching fractions or the upper limits on the branching fractions of these decay modes, which areAmong these results, the measurements of B(Ψ(3770)→Φπ0π0) and B(Ψ(3770)→ΦKS0KS0) are done for the first time in experiment. Evidence for Ψ(3770)→ Φπ+π-with a significance of about3.1times standard deviation(σ)are found, corresponding to the upper limit of4.9×10-4at90％C.L..In this thesis,we have also measured the branching fraction of Ψ(3686)→Φπ+π-,Φπ0π0,ΦK+K-and ΦKS0+KS0,with the world’s largest Ψ(3686)data sam-ple.The results areAmong these results,the branching fraction of Ψ(3686)→Φπ0π0and Ψ(3686)→ΦKS0+KS0are measured for the first time in experiment.B(Ψ(3686)→Φπ+π-) and B(Ψ(3686)→ΦK+K-)agree with the PDG averaged value well.but with better precisions.The results in this thesis proyide important experimental information for the understanding of Ψ(3770)non-DD decays and "pπ" puzzle in Ψ(3686)decays.更多还原