Polarizations and spin correlations in the ΔN→ΔNreaction

A systematic formalism is developed for the spin observables of the Δ N →Δ N reaction, according to the polarization states of the four particles involved in the reaction. This formalism allows us to express all observables by means of a compact formula. Special emphasis is put on the search for relationships between different spin observables. A methodology is given for selecting a set of 39 observables, which determines the 20 magnitudes of the amplitudes and 19 independent relative phases between them.