Using multiple scattering theory the scattering lengths of η mesons on helium nuclei are calculated and checked against final state η interactions from the pd→${\mathrm{\eta }}^3$He and dd→${\mathrm{\eta }}^4$He reactions. The existence of an ${\mathrm{\eta }}^4$He quasibound state is indicated.

• Received 1 February 1995

DOI:https://doi.org/10.1103/PhysRevC.52.544