Scalar mesons and polarizability of the nucleon

TL;DR

This paper demonstrates that scalar mesons like $\sigma$, $f_0(980)$, and $a_0(980)$ as t-channel exchanges explain the nucleon's electric polarizability and its diamagnetic properties, aligning with experimental data.

Contribution

It introduces scalar mesons as key t-channel exchanges that resolve the nucleon polarizability puzzle, providing a quantitative explanation for previously missing contributions.

Findings

Scalar mesons account for the nucleon's diamagnetism.

The model confirms a two-photon width of the $\sigma$ meson as approximately 2.58 keV.

The approach explains the large electric polarizability of the proton.

Abstract

It is shown that the scalar mesons $\sigma$, $f_0(980)$ and $a_0(980)$ as $t$-channel exchanges quantitatively solve the problem of diamagnetism and give an explanation of the large missing part of the electric polarizability $\alpha$ showing up when only the pion cloud is taken into account. The electric polarizability of the proton $\alpha_p$ confirms a two-photon width of the $\sigma$ meson of $\Gamma_{\sigma\gamma\gamma}=(2.58\pm 0.26)$ keV.