QCD非微扰方法在强子与核物理中的应用研究

The low energy nonperturbative characteristic of Quamtum chromodynamics (QCD) is inevitably involved in the study on the properties and decays of hadrons at quark level. Therefore, the study on the structures, properties and decays through QCD nonperturbative methods has been one of the hotspots in particle and nuclear physics all the time. As effective nonperturbative approaches to low energy QCD, the QCD sum rule and light-cone QCD sum rule have been widely used in hadronic physics although the certification of their applicability and reliability has not yet been finished. This project is to study the properties of hadrons and the relevant physical processes by the two nonperturbative approaches above under the frameworks of full QCD and its effective theories. The application range will be broaden and the understanding of the nonperturbative effect of QCD which involed in these processes will be deepen. We will also examine the reliability of the results. The main content this project will study on includes the semileptonic and rare decays of heavy flavor hadrons, the properties of new hadronic states, the electromagnetic form factors of baryons, the effective couplings of strong interactions between hadrons, and so on. This project will take close attention to the progresses of accelerator experiments from home and abroad, such as LHC, and try to interplet the new results or give further predictions.

在夸克层次研究强子性质和衰变必然会涉及到量子色动力学（QCD）的低能非微扰特性，因此用QCD非微扰方法来研究强子的结构、性质和衰变一直以来都是粒子物理与核物理研究的热点之一。QCD求和规则与光锥QCD求和规则方法作为低能QCD的有效非微扰途径在强子物理研究中的应用相当广泛，不过它们的适用范围和可靠性的论证还远没有完成。本项目拟在QCD完整理论及其有效理论框架下，用这两种非微扰方法研究强子的性质和相关的物理过程，拓展其应用，理解其中的QCD非微扰效应，并对结果的可靠性进行探讨。研究内容具体包括重味强子的半轻衰变、稀有衰变，新强子态的性质和重子的电磁形状因子，以及强子间的有效强耦合系数等。本项目将密切关注国内外各加速器实验（如LHC等）的最新进展，研究其中的物理，对实验结果作出解释或者给出进一步的预言。

近年来，强子物理作为高能物理与核物理交叉领域，已经成了理论和实验新的研究热点。随着LHC、BESIII等高能物理实验数据的积累，许多新强子态陆续在实验中被发现。关于它们的结构和动力学的研究涉及到量子色动力学（QCD）非微扰效应，需要用QCD非微扰方法进行处理。本项目成功地将QCD求和规则、光锥求和规则等非微扰方法应用于强子物理的一些过程的研究，特别是重味强子的衰变和新强子态的产生等动力学过程，拓展了这些非微扰方法的应用范围。通过理论分析，我们用光锥求和规则估计了重味重子稀有辐射衰变和稀有半轻衰变过程的形状因子，得到相应的跃迁矩阵元，从而得到这些过程的衰变宽度和分支比，理论计算与实验结果吻合较好。这个工作对于精确分析重味强子的稀有过程，探索超出标准模型的新物理具有一定的参考意义。我们还在重夸克有效理论（HQET）框架下，用QCD求和规则的方法分析了Bs介子到重味新强子态DsJ(2860)的半轻衰变过程，得到衰变宽度和分支比。结果表明，当DsJ(2860)取不同自旋宇称量子数时，得到的分支比差别很大。这个工作对于指导实验测量相应衰变道，澄清DsJ(2860)的结构具有一定的参考意义。