摘要
本文研究了质子和中子的类时电磁形状因子.作者基于手征有效场论,通过求解李普曼-施温格方程得到了核子-反核子对散射振幅.以此为输入,利用扭曲波恩近似方法描述了核子末态相互作用,计算了正负电子湮灭到正反核子对的过程.通过拟合相移、截面以及微分截面等实验数据,定下了有效场论的未知耦合常数.进一步研究发现,可以利用两个分数振荡振子来描述核子电磁类时形状因子的振荡行为:一个表现为过阻尼振荡,在阈值附近占主导地位;另一个类似于欠阻尼振荡,在高能区起到重要作用.这种振荡行为对理解硬光子诱导的核子内部极化电荷的分布起着至关重要的作用.
The electromagnetic form factors of the proton and the neutron in the timelike region are investigated.Electron–positron annihilation into antinucleon-nucleon(NN)pairs is treated in distorted wave Born approximation,including the final-state interaction in the NN system.The latter is obtained by a Lippmann–Schwinger equation for NN potentials derived within SU(3)chiral effective field theory.By fitting to the phase shifts and(differential)cross section data,a high quality description is achieved.With these amplitudes,the oscillations of the electromagnetic form factors of the proton and the neutron are studied.It is found that each of them can be described by two fractional oscillators.One is characterized as‘‘overdampedo and dominates near the threshold,while the other is‘‘underdampedo and plays an important role in the high-energy region.These two oscillators are essential to understand the distributions of polarized electric charges induced by hard photons for the nucleons.
作者
杨勤鹤
郭棣
戴凌云
Johann Haidenbauer
康现伟
Ulf-GMeiner
Qin-He Yang;Di Guo;Ling-Yun Dai;Johann Haidenbauer;Xian-Wei Kang;Ulf-GMeier(School of Physics and Electronics,Hunan University,Changsha 410082,China;Hunan Provincial Key Laboratory of High-Energy Scale Physics and Applications,Hunan University,Changsha 410082,China;Institute for Advanced Simulation,Institut für Kernphysik and Jülich Center for Hadron Physics,Forschungszentrum Jülich,Jülich D-52425,Germany;Key Laboratory of Beam Technology of the Ministry of Education,College of Nuclear Science and Technology,Beijing Normal University,Beijing 100875,China;Institute of Radiation Technology,Beijing Academy of Science and Technology,Beijing 100875,China;Helmholtz Institut für Strahlen-und Kernphysik and Bethe Center for Theoretical Physics,Universität Bonn,Bonn D-53115,Germany;Tbilisi State University,Tbilisi 0186,Georgia)
基金
supported by Joint Large Scale Scientific Facility Funds of the National Natural Science Foundation of China(NSFC)and Chinese Academy of Sciences(CAS)(U1932110,NSFC(11805059,11805012,11675051,12322502),and 12335002)
Fundamental Research Funds for the central Universities
supported by Deutsche Forschungsgemeinschaft(DFG)(TRR110)
NSFC through funds provided to the Sino-German CRC 110“Symmetries and the Emergence of Structure in QCD”(11621131001)
supported in part by VolkswagenStiftung(93562)
by the CAS President’s International Fellowship Initiative(PIFI)(2018DM0034)。
