Phenomenological analysis of the double pion production in nucleon-nucleon collisions up to 2.2 GeV

TL;DR

This paper uses an effective Lagrangian approach to analyze double pion production in nucleon-nucleon collisions up to 2.2 GeV, identifying dominant resonances and reproducing cross sections consistent with experimental data.

Contribution

It provides a detailed phenomenological analysis of NN to NN pi pi channels including various resonances, extending understanding of resonance contributions in pion production.

Findings

Dominance of N*(1440)→ Nσ near threshold for isospin zero channels.

Large contributions from N*(1440)→ Δπ and Δ(1600)→ N*(1440)π at higher energies.

Reproduces total and differential cross sections up to 2.2 GeV, matching experimental data.

Abstract

With an effective Lagrangian approach, we analyze several NN \to NN\pi\pi channels by including various resonances with mass up to 1.72 GeV. For the channels with the pion pair of isospin zero, we confirm the dominance of N*(1440)\to N\sigma in the near threshold region. At higher energies and for channels with the final pion pair of isospin one, we find large contributions from N*(1440)\to \Delta\pi, double-Delta, \Delta(1600) \to N*(1440)\pi, \Delta(1600) \to \Delta\pi and \Delta(1620) \to \Delta\pi. There are also sizeable contributions from \Delta \to \Delta\pi, \Delta \to N\pi, N \to \Delta\pi and nucleon pole at energies close to the threshold. We well reproduce the total cross sections up to beam energies of 2.2 GeV except for the pp\to pp\pi^0\pi^0 channel at energies around 1.1 GeV and our results agree with the existing data of differential cross sections of pp \to pp\pi^+\pi^-, pp \to nn\pi^+\pi^+ and pp \to pp\pi^0\pi^0 which are measured at CELSIUS and COSY.