Spin selectivity of dd → αX reaction and its applications in hadron physics

The dd → αX reaction exhibits strong selectivity for the isospin, spin and parity of the X system. The charge symmetry requires that the X system should have isospin equal 0. The particle identity and conservations of the total angular momentum and parity impose very strong constraints on quantum numbers allowed in the reaction. This leads to very strong selectivity when α is emitted at 0° or 180°, as well as in the case of reactions at threshold. These features may be used to measure directly the individual partial wave contributions in the production reactions and to determine directly the spin and parity of the X system. Such kind of applications will be discussed for the charge symmetry forbidden dd → απ⁰ reaction, the investigations of the σ meson in the dd → ασ reaction and in studies of the dd → αγ reaction.