Investigation of light scalar resonances at COSY

TL;DR

This paper reviews theoretical models of the $a_0$(980) and $f_0$(980) resonances and discusses how COSY experimental data on various collisions can help distinguish between these models, especially through isospin-violating reactions.

Contribution

It analyzes COSY data on meson production to differentiate between models explaining the structure of light scalar resonances.

Findings

COSY data can potentially distinguish between different theoretical models

Measurement of $dd o ^4He o ext{mesons}$ reactions is promising for studying isospin violation

The $a_0$-$f_0$ mixing can be probed through specific collision experiments

Abstract

The $a_0$(980) and $f_0$(980) resonances are two well established states in the excited meson spectrum. We review the most prominent theoretical models which try to explain the structure of these states. It is discussed whether data from COSY on $a_0$ and $f_0$ production in $pp$, $pn$, $pd$ and $dd$ collisions allow to distinguish between the different approaches. Very promising in this respect seems to be the measurement of the reaction $dd \to (\mathrm{^4He} a_0^0 \to) \mathrm{^4He} \pi^0\eta$ which violates isospin conservation and can be related to $a_0$-$f_0$ mixing.