On classical description of radiation from neutral fermion with anomalous magnetic moment

Electromagnetic radiation from an uncharged spin 1/2 particle with an anoma lous magnetic moment moving in the classical electromagnetic external field originates from quantum spin-flip transitions. Although this process has a purely quantum nature, it was observed for certain particular external fie ld configurations that, when quantum recoil is neglected, the radiation pow er corresponds to the classical radiation from an evolving magnetic dipole. We argue that this correspondence has a more general validity in the case of an unpolarized particle and derive a general formula for radiation in te rms of the external field strength and its derivative. A classical dynamics of the spin is described by the Bargmann-Michel-Telegdi equation. (C) 2000 Elsevier Science B.V. All rights reserved.