New experimental data on the $pd\to {}^3\mathrm{He}{\pi }^{+}{\pi }^{-}$ reaction obtained with the COSY-MOMO detector below the three-pion threshold are presented. The reaction was also studied in inverse kinematics with a deuteron beam and the higher counting rates achieved were especially important at low excess energies. The comparison of these data with inclusive $pd\to {}^3\mathrm{He}{X}^0$ rates allowed estimates also to be made of ${\pi }^0{\pi }^0$ production. The results confirm our earlier findings that, close to threshold, there is no enhancement at low excitation energies in the ${\pi }^{+}{\pi }^{-}$ system, where the data seem largely suppressed compared with phase space. Possible explanations for this behavior, such as strong $p$ waves in the ${\pi }^{+}{\pi }^{-}$ system or the influence of two-step processes, are explored.

• Received 3 August 2016

DOI:https://doi.org/10.1103/PhysRevC.94.034618