Double pion production in $NN$ and $\bar{N}N$ collisions

With an effective Lagrangian approach, we give a full analysis on the $NN \to NNππ$ and $\bar{N}N\to \bar{N}Nππ$ reactions by exploring the roles of various resonances with mass up to 1.72 GeV. We find large contributions from $Δ$, $N^*(1440)$, $Δ(1600)$ and $Δ(1620)$ resonances. Our calculations also indicate sizeable contributions from nucleon poles for the energies close to the threshold. A good description to the existing data of different isospin channels of $NN\to NNππ$ and $\bar{N}N\to \bar{N}Nππ$ for beam energies up to 2.2 GeV is reached. Our results provide important implications to the ABC effect and guildlines to the future experimental projects at COSY, HADES and HIRFL-CSR. We point out that the PANDA at FAIR could be an essential place for studying the properties of baryon resonances and the data with baryon and anti-baryon in final states are worth analyzing.

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