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Differential technique for the covariant orbital angular momentum operators
The orbital angular momentum operator expansion turns out to be a powerful tool to construct
the fully covariant partial wave amplitudes of hadron decay reactions and hadron photo- and electroproduction
processes. In this paper we consider a useful development of the orbital angular momentum operator
expansion method. We present the differential technique allowing the direct calculation of convolutions of
two orbital angular momentum operators with an arbitrary number of open Lorentz indices. This differential
technique greatly simplifies calculations when the reaction subject to the partial wave analysis involves
high spin particles in the initial and/or final states. We also present a useful generalization of the orbital
angular momentum operators.