Chinese Acad Sci, Inst High Energy Phys, Beijing 100039, Peoples R China
The analytic helicity amplitudes of Z --> 3 gamma, gamma gamma --> Z gamma and gammaZ --> gamma gamma via W-loop and charged scalar-loop are presented. There is some difference between our results and those in Ref. 13 for Z --> 3 gamma via W-loop and fermion-loop, which has different physical meanings. We have calculated the unpolarized and polarized cross-sections for gamma gamma --> gammaZ process. We find that the total cross-section of gamma gamma --> gammaZ is larger than that of gamma gamma --> gamma gamma at 500 GeV of gamma gamma c.m.s. energy. In principle this process provides a test of the non-Abelian nature of the standard model.