We discuss radiation zeros that are found in gauge tree amplitudes for processes involving multiphoton emission. Previous results are clarified by examples and by further elaboration. The conditions under which such amplitude zeros occur are identical in form to those for the singlephoton zeros, and all radiated photons must travel parallel to each other. Any other neutral particle likewise must be massless (e.g., gluon) and travel in that common direction. The relevance to questions such as gluon jet identification and computational checks is considered. We use examples to show how certain multiphoton amplitudes evade the zeros, and to demonstrate the connection to a more general result, the decoupling of an external electromagnetic plane wave in the "null zone." Brief comments are made about zeros associated with other gauge-boson emission.

• Received 16 August 1993

DOI:https://doi.org/10.1103/PhysRevD.49.2290