Charge symmetry breaking in dd→He4π0 with WASA-at-COSY

Charge symmetry breaking (CSB) observables are a suitable experimental tool to examine effects induced by quark masses on the nuclear level. Previous high precision data from TRIUMF and IUCF are currently used to develop a consistent description of CSB within the framework of chiral perturbation theory. In this work the experimental studies on the reaction dd→He4π0 have been extended towards higher excess energies in order to provide information on the contribution of p  -waves in the final state. For this, an exclusive measurement has been carried out at a beam momentum of pd=1.2 GeV/cpd=1.2 GeV/c using the WASA-at-COSY facility. The total cross section amounts to σtot=(118±18stat±13sys±8ext) pbσtot=(118±18stat±13sys±8ext) pb and first data on the differential cross section are consistent with s-wave pion production.