Elastic Scattering of $^6$He based on a Cluster Description

Recently elastic scattering of $^6$He off a polarized proton target has been measured for the first time at an energy of 71~MeV/nucleon. The experiment finds that the analyzing power becomes negative around 50$^{\circ}$, a feature which can not be described by simple folding models for the optical potential, which do not take into account the halo character of the $^6$He nucleus. In this work, the cluster structure of $^6$He is incorporated in an optical potential for the reaction $p+^6$He in the framework of the Watson ansatz for the multiple scattering theory. We find that the analyzing power at 71~MeV/nucleon is sensitive to the cluster structure of $^6$He, whereas the differential cross section is not. We also present predictions for higher energies which also show a lack of sensitivity.