Spin observables of the reaction pd→3Heη and quasi-bound 3He-η pole

A formalism for spin observables of the reaction pd -> He-3 eta is derived in a model independent way. The general case with a full set of six independent spin amplitudes is studied. Furthermore, approximations by five and four spin amplitudes are investigated in the near threshold region. This region is of great interest to search for a quasi-bound He-3-eta state, in particular, by measurement of energy dependence of relative phases of s- and p-wave amplitudes. Complete polarization experiments, allowing determination of spin amplitudes, are analyzed. It is shown that measurement of only analyzing powers and spin correlation coefficients hardly allows one to separate the s- and p-wave amplitudes, but additional measurement of polarization transfer coefficients simplifies this problem. Specific observables, given by products of one sand one p-wave amplitudes, are found. Measurement of these observables will provide new independent information on the He-3-eta pole position. (c) 2008 Elsevier B.V. All rights reserved.