Analyzing-power measurement in p→n→${\pi }^{\mathrm{-}}$pp${(}^1$$S_0$): Pion absorption by quark clusters?

We have measured analyzing powers in d(p→,${\pi }^{\mathrm{-}}$pp)p at a beam energy of 400 MeV and laboratory pion detector angles of 35° and 43°. The ${\pi }^{\mathrm{-}}$ and two of the outgoing protons were detected in coincidence in a geometry which selected the quasifree two-body reaction pn→${\pi }^{\mathrm{-}}$pp${(}^1$ $S_0$). The analyzing-power data combined with ${}_{}{}^3{}_{}{}^{}\mathrm{He}$(${\pi }^{\mathrm{-}}$,pn)n differential cross sections allow determination of the transition amplitudes. The results indicate a significant contribution from a very short-range part of the nucleon-nucleon interaction.