Helicity Dependent Distribution Functions of the Proton and $\Lambda$ and $\Sigma^0$ Baryons

TL;DR

This paper uses continuum Schwinger function methods to predict the helicity-dependent and unpolarised distribution functions of proton, $\Lambda$, and $\Sigma^0$ baryons, revealing the effects of diquark correlations and SU(3) symmetry breaking.

Contribution

It provides the first coherent set of predictions for baryon distribution functions, including novel insights into diquark effects and gluon contributions to baryon spin.

Findings

Valence-quark DFs ratios in the proton are presented.

Axialvector diquarks are crucial for the spin structure of $\Sigma^0$.

Gluons carry about 40% of the baryons' spin at typical measurement scales.

Abstract

Using continuum Schwinger function methods, a coherent set of predictions for proton, $\Lambda$ and $\Sigma^0$ distribution functions (DFs) has been made available -- both helicity dependent and unpolarised. The results and comparisons between them reveal impacts of diquark correlations and SU$(3)$-flavour symmetry breaking, some of which are highlighted in this contribution. For instance: in-proton ratios of helicity-dependent/unpolarised valence-quark DFs are presented; it is highlighted that, were it not for the presence of axialvector diquarks in the $\Sigma^0$, the valence strange quark would carry none of the $\Sigma^0$ spin; and the sign and size of polarised gluon DFs is discussed -- at a scale typical of modern measurements, gluon partons carry roughly 40% of each octet baryon's spin.