Is there an ηHe3 quasi-bound state?

The observed variation of the total cross section for the dp→He3η reaction near threshold means that the magnitude of the s-wave amplitude falls very rapidly with the η centre-of-mass momentum. It is shown here that recent measurements of the momentum dependence of the angular distribution imply a strong variation also in the phase of this amplitude. Such a behaviour is that expected from a quasi-bound or virtual ηHe3 state. The interpretation can be investigated further through measurements of the deuteron or proton analysing powers and/or spin-correlations.