非微扰QCD是目前粒子物理学的前沿课题，psi(3686)到eta_c的强子跃迁过程是研究psi(3686)强子跃迁机制的重要内容之一，是研究非微扰QCD理论的重要方式。2009年和2012年，BESIII采集了目前世界上最大的psi(3686)数据样本，为研究psi(3686)到eta_c强子跃迁机制提供了机遇。本申请第一次在BESIII实验上提出利用psi(3686)到 eta_c的强子跃迁过程对psi(3686)的强子跃迁机制进行研究，考虑到末态粒子动量分布及BESIII对pi介子探测效率随动量的变化关系，主要分析psi(3686)→eta_c pi^+ pi^- pi^0 和 psi(3686)→eta_c pi^+ pi^- 两个过程，测量它们的衰变分支比，为psi(3686)强子跃迁机制的研究提供可靠且必不可少的实验数据，从而为发展非微扰QCD理论提供现实依据。

Non-perturbative QCD is a frontier hot topic in particle physics currently. As one of the important member of charmonium states, psi(3686) hadronic transition provides an essential way in non-perturbative QCD theory study. In 2009 and 2012, BESIII detector collected the largest statistics of psi(3686) datasets in the world and the performance of BESIII detector is quite well until now. It therefore provides an unprecedented opportunity for studying psi(3686) hadronic transition mechanism by its decaying to eta_c. In this proposal, psi(3686)→eta_c pi^+ pi^- pi^0 and psi(3686)→eta_c pi^+ pi^- are chosen to study the hadronic transition of psi(3686) to eta_c as they have simpler final states and less kinematical constrains on momentum. First, the branching ratio of the two decay channels will be obtained, and then momentum and angular distributions of final states will be provided if the statistics is enough. Results will offer the experimental basis in understanding the hadronic transition mechanism of psi(3686) and advance the development of non-perturbative QCD.