【作者】 金丹；

【导师】 杨亚东；

【作者基本信息】 华中师范大学 ， 理论物理， 2012， 博士

【摘要】 强子的电磁形状因子对于描述遍举反应机制来说是非常重要的物理观测量。对它们的研究不仅为我们提供了一些关于强子内部结构的有用的信息,而且在帮助我们理解中间能区从微扰到非微扰行为的转变方面起了关键的作用,从而为检验微扰QCD(PQCD)理论的正确性提供了有用的测试平台。由于强子的电磁形状因子是非常热门的研究课题,因此在过去的几十年中,不管在实验还是理论上都存在着大量关于它们的基于各种各样不同方法的研究。本论文致力于在PQCD因子化框架下,通过模型与PQCD计算相结合的方法给出关于两种最轻赝标介子(π和K)的类空与类时电磁形状因子在中间能区的唯象的研究。首先我们简单回顾了介子电磁形状因子在实验和理论上的研究方法,同时也简单介绍了赝标介子的光锥分布振幅。然后,在最近的CLEO实验数据的激励下,通过使用QCD强耦合常数αs。(Q2)的解析模型和红外固定的胶子传播子,我们同时分析了基于PQCD因子化理论的pion介子和kaon介子的类空与类时电磁形状因子,并将我们的计算结果与目前可获得的实验数据进行了比较。我们的分析表明在低和中间动量转移,与标准的领头阶2-扭度微扰贡献相比,来自非微扰效应和介子3-扭度光锥分布振幅的贡献显得很重要,它们应该被考虑进来。除此之外,我们的结果能够合理地描述当前在中间能区存在的实验数据包括CLEO实验数据和J／Ψ结果。最后,我们需要指出的是尽管最近的CLEO实验数据给出了pion介子和kaon介子在类时动量转移|Q2|=13.48 GeV2时的电磁形状因子的精确的测量结果,然而在相对高能区域,目前仍然缺少准确的实验数据。希望在将来,随着实验数据的进一步完善和精确,它们能为理论预测提供一个更好的检验平台。更多还原

【Abstract】 The electromagnetic form factors of hadrons are important physical observables for the de-scription of exclusive reaction mechanisms. The study of them not only provide useful informa-tion concerning the internal structures of the hadrons, but also play a key role in understanding the transition from the perturbative to the non-perturbative behavior at intermediate energies, providing useful grounds to check the rightness of the perturbative QCD (PQCD) theory. Since the electromagnetic form factors of hadrons are such a popular topic that there have been exten-sive experimental and theoretical studies of them based on various different approaches during the past few decades. This thesis is devoted to give a phenomenological study of the space-and time-like electromagnetic form factors of the two lightest pseudoscalar mesons (πand K) in the intermediate energy region within the framework of PQCD factorization by a combination of model and PQCD calculations.We first give a brief review on the both experimental and theoretical study methods of the meson electromagnetic form factors and the light-cone (LC) distribution amplitudes (DAs) of the pseudoscalar meson. Then, motivated by the recent CLEO data, we present a combined analysis of the space-and time-like pion and kaon electromagnetic form factors in factorized PQCD by employing an analytic model for as(Q2) and an infrared (IR) finite gluon propagator and compare our results with the presently available experimental data. Our analysis shows that at low and moderate momentum transfers, compared with the standard LO twist-2 perturbative contribution, the contributions from the non-perturbative effects and the twist-3 meson LC DAs are important and should be took into account, in addition, the existing experimental data at moderate energies, including the CLEO data and J/ψresult can be reasonably well described by our results. To this end, we should point out that although the recent CLEO data provide the first precision measurements of the pion and kaon electromagnetic form factors for time-like momentum transfer ofQ2= 13.48 GeV, there is still lack of the accurate experimental data in the relative high energy region. Hopefully, with the availability of better quality experimental data in the future, there could be a better testing ground for theoretical predictions.更多还原