Investigation of the dd\rightarrow $^{3}Hen\pi ^{0}$ reaction with the FZ Jülich WASA-at-COSY facility

An exclusive measurement of the dd\rightarrow $^{3}Hen\pi^{0}$ eaction was carried out at a beam momentum of $p_{d}$=1.2 GeV/c using the WASA-at-COSY facility. Information on the total cross section as well as differential distributions was obtained. The data are described by a phenomenological approach based on a combination of a quasifree model and a partial wave expansion for the three-body reaction. The total cross section is found to be $\sigma _{tot}= \left ( 2.89\pm 0.01_{stat}\pm 0.06_{sys}\pm 0.29_{norm} \right )\mu b$. The contribution of the quasifree processes (with the beam or target neutron being a spectator) accounts for 38% of the total cross section and dominates the differential distributions in specific regions of phase space. The remaining part of the cross section can be described by a partial wave decomposition indicating the significance of p-wave contributions in the final state.