Ay. Ignatiev et Gc. Joshi, ELECTRON-POSITRON ANNIHILATION INTO DIRAC MAGNETIC MONOPOLE AND ANTIMONOPOLE - THE STRING AMBIGUITY AND THE DISCRETE SYMMETRIES, Modern physics letters A, 13(28), 1998, pp. 2295-2304
We address the problem of string arbitrariness in the quantum field th
eory of Dirac magnetic monopoles. Different prescriptions are shown to
yield different physical results. The constraints due to the discrete
symmetries (C and P) are derived for the process of electron-positron
annihilation into the monopole-antimonopole pair. In the case of the
annihilation through the one-photon channel, the production of spin-0
monopoles is absolutely forbidden; spin-1/2 monopole and antimonopole
should have the same helicities (or, equivalently, the monopole-antimo
nopole state should be p-wave P-1(1)).