The reaction np→ ηd near threshold

We have calculated the cross section for the process np→ ηd in the region near threshold, within the framework of a three-body model. We studied the dependence of the cross section to the production mechanism and to the initial- and final-state interactions. We found that the magnitude of the cross section is highly dependent on the reaction mechanism. However, its shape is essentially determined by the ηd final-state interaction alone. This strong signature in mm directly provides information about the ηN scattering length. For a variety of reaction mechanisms it is verified that the np→ ηd experimental data can only be explained if the ηN scattering length has a small real part, as it happens, for instance, in the ηN interaction model proposed recently by the Jülich group.