Differential cross section and analysing power of the quasi-free pn -> {pp}_s pi- reaction at 353 MeV

TL;DR

This study measures the differential cross section and analysing power of a specific pion production reaction at 353 MeV, linking p-wave pion production to three-nucleon scattering through detailed partial wave analysis.

Contribution

It provides new experimental data and a comprehensive partial wave analysis of the quasi-free pn -> {pp}_s pi^- reaction at 353 MeV, connecting it to related reactions.

Findings

Data on differential cross section and analysing power obtained.

Full partial wave decomposition performed for both reactions.

Results support theoretical models of pion production amplitudes.

Abstract

In order to establish links between p-wave pion production in nucleon-nucleon collisions and low energy three-nucleon scattering, an extensive programme of experiments on pion production is currently underway at COSY-ANKE. The final proton pair is measured at very low excitation energy, leading to an S-wave diproton, denoted here as {pp}_s. By using a deuterium target we have obtained data on the differential cross section and analysing power of the quasi-free pol{p}n -> {pp}_s pi^- reaction at 353 MeV. The spectator proton p_sp was either measured directly in silicon tracking telescopes or reconstructed using the momentum of a detected pi^-. Both observables can be described in terms of s-, p-, and d-wave pion production amplitudes. Taken together with the analogous data on the pol{p}p -> {pp}_s pi^0 reaction, full partial wave decompositions of both processes were carried out.