Pure sea-quark contributions to the magnetic form factors of $\Sigma$ baryons

TL;DR

This paper predicts large sea-quark contributions to the magnetic form factors of Sigma baryons using chiral effective field theory, highlighting their potential for experimental and lattice QCD studies of baryon structure.

Contribution

It introduces the first detailed prediction of sea-quark contributions to Sigma baryon magnetic form factors using a finite range regularization approach in chiral effective field theory.

Findings

Sea-quark contributions are about seven times larger than the nucleon strange magnetic moment.

Predicted u- and d-quark contributions to Sigma baryons are significantly larger than strange contributions in nucleons.

Results suggest promising observables for future lattice QCD and experimental investigations.

Abstract

We propose the pure sea-quark contributions to the magnetic form factors of $\Sigma$ baryons, $G_{\Sigma^-}^u$ and $G_{\Sigma^+}^d$, as priority observables for the examination of sea-quark contributions to baryon structure, both in present lattice QCD simulations and possible future experimental measurement. $G_{\Sigma^-}^u$, the $u$-quark contribution to the magnetic form factor of $\Sigma^-$, and $G_{\Sigma^+}^d$, the $d$-quark contribution to the magnetic form factor of $\Sigma^+$, are similar to the strange quark contribution to the magnetic form factor of the nucleon, but promise to be larger by an order of magnitude. We explore the size of this quantity within chiral effective field theory, including both octet and decuplet intermediate states. The finite range regularization approach is applied to deal with ultraviolet divergences. Drawing on an established connection between quenched and full QCD, this approach makes it possible to predict the sea quark contribution to the magnetic form factor purely from the meson loop. In the familiar convention where the quark charge is set to unity $G_{\Sigma^-}^u = G_{\Sigma^+}^d$. We find a value of $-0.38^{+0.16}_{-0.17}\ \mu_N$, which is about seven times larger than the strange magnetic moment of the nucleon found in the same approach. Including quark charge factors, the $u$-quark contribution to the $\Sigma^-$ magnetic moment exceeds the strange quark contribution to the nucleon magnetic moment by a factor of 14.