[Chen, Hong-Yu
; Zhou, Hai-Qing] Southeast Univ, Dept Phys, Nanjing 211189, Jiangsu, Peoples R China
; [Zhou, Hai-Qing] Chinese Acad Sci, Inst Theoret Phys, State Key Lab Theoret Phys, Beijing 100190, Peoples R China
英文摘要:
A new form of two-photon exchange (TPE) effect is studied to explain the discrepancy between unpolarized and polarized experimental data in elastic ep scattering. The mechanism is based on a simple idea that apart from the usual TPE effects from box and crossed-box diagrams, the mesons may also be exchanged in elastic ep scattering by two-photon coupling at loop level. The detailed study shows such contributions to reduced unpolarized cross section (sigma(un)) and polarized observables (P-t, P-l) at fixed Q(2) are only dependent on proton's electromagnetic form factors G(E,M) and a new unknown universal parameter g. After combining this contribution with the usual TPE contributions from box and crossed-box diagrams, the ratio mu(p)G(E)/G(M) extracted from the recent precise unpolarized and polarized experimental data can be described consistently.
Chen, HY,Zhou, HQ. Meson exchange effects in elastic ep scattering at loop level and the electromagnetic form factors of the proton[J]. PHYSICAL REVIEW C,2014,90(4):45205.
