Classical radiation zeros in gauge-theory amplitudes. II. Spin-dependent null zone

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Abstract
Further aspects of tree-amplitude zeros, occurring only for certain helicity configurations and representative of the complementary radiation theorem, are considered. These polarization-dependent zeros are destroyed by nongauge interactions and correspond, in the low-frequency limit, to the classical result where there is no radiation polarized perpendicular to the scattering plane. The zeros found by Hellmund and Ranft and by Cortés, Hagiwara, and Herzog are discussed and are contrasted with the zeros of Gaemers and Gounaris. Additional experiments are suggested.