Scalar mesons in eta' -> eta pi0 pi0 decay

TL;DR

This paper models the decay of eta' into eta and two neutral pions, demonstrating that including a0 and sigma meson contributions, with a novel sigma propagator, aligns well with experimental data.

Contribution

It introduces a new parametrization of the sigma meson propagator that satisfies fundamental physical constraints and improves decay modeling accuracy.

Findings

Dominant a0-meson contribution to decay.

Sigma-meson essential for Dalitz plot shape.

New sigma propagator matches pi-pi scattering data.

Abstract

The decay $\eta'\to\eta\pi^{0}\pi^{0}$ is studied in the framework of isobar model. It is shown, that good agreement with the experiment is achieved if $a_0$- and $\sigma$-meson contributions are taken into account. The contribution of $a_0$-meson is dominant, but $\sigma$-meson is necessary to reproduce the form of experimental Dalitz plot. Instead of usual Breit-Wigner form of $\sigma$-meson propagator we use parametrization of $\pi\pi$-amplitude, that satisfies analiticity, crossing, unitarity and chirality constraints. This amplitude has a pole in complex plane, that corresponds to $\sigma$-meson and describe experimental data on $\pi\pi$-scattering in $K_{e4}$ decay.