Singlet cross section and the tensor interaction in $\bar{\mathrm{p}}\mathrm{p}\to \bar{\mathrm{\Lambda }}\mathrm{\Lambda }$

In this short paper, we demonstrate using irreducible tensorial techniques and in a model-independent way, why tensor interactions and also orbital-angular momentum-changing vector interactions are absent in the singlet unpolarized differential cross section for the reaction $\bar{\mathrm{p}}\mathrm{p}\to \bar{\mathrm{\Lambda }}\mathrm{\Lambda }$.