Search for η-mesic nuclei in a recoil-free transfer reaction

Abstract

We have studied the reaction p+²⁷Al → ³He+p+Π^-+X at recoil-free kinematics. An η meson possibly produced in this reaction would be thus almost at rest in the laboratory system and could therefore be bound with high probability, if nuclear η states exist. The decay of such a state through the N^∗(1535) resonance would lead to a proton-Π^- pair emitted in opposite directions. For these conditions we find some indication of such a bound state. An upper limit of ≈0.5 nb is found.