Photon splitting above the pair creation threshold in a strong magnetic field

Abstract

The process of photon splitting $\gamma \to \gamma \gamma$ in a strong magnetic field is investigated both below and above the pair creation threshold. Contrary to the statement by Baier et al., the ``allowed'' channel $\text{alw}$ is shown not to be a comprehensive description of splitting in the strong field because the ``forbidden'' channel $\text{frb}$ is also essential. The partial amplitudes and the splitting probabilities are calculated taking account of the photon dispersion and large radiative corrections near the resonance.

Comments: 13 pages, 3 figures, LaTeX, uses epsf.sty, numerical error in eq.(11) corrected, typos fixed, presentation improved, accepted to Physics Letters B