High precision studies on angular asymmetries of the differential cross sections in the d+p → ³He+η reaction

Investigations on the total and differential cross sections of the reaction d+p→³He+η are of special interest since they differ strongly from a pure phase space behavior near threshold. Furthermore, analyses of the asymmetry factor α of the differential cross sections show a distinct effect of s- and p-wave interference, which can be explained by a rapid variation of the relative phase. These effects are an indication for an unexpected strong final state interaction (FSI) between η mesons and ³He nuclei which could lead to a quasi bound state of the ³Heη-system. Current investigations on high precision data at the internal fixed target experiment ANKE of the storage ring COSY enable the extraction of additional total and differential cross sections for the η production up to an excess energy of Q=15 MeV. These cross sections will significantly improve the accuracy, which will allow to study the behavior of the asymmetry factor α with high resolution. Recent results are presented and discussed.