Distribution Functions of $\Lambda$ and $\Sigma^0$ Baryons

TL;DR

This paper models $\Lambda$ and $\Sigma^0$ baryons as quark-diquark bound states using a symmetry-preserving contact interaction to predict their unpolarised and polarised distribution functions, highlighting the effects of diquark correlations and SU(3) symmetry breaking.

Contribution

It provides the first comprehensive predictions for $\Lambda$ and $\Sigma^0$ baryon distribution functions using a contact interaction model, emphasizing diquark effects and symmetry breaking.

Findings

Diquark correlations significantly influence baryon structure functions.

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

The model explains features of baryon spin decomposition and gluon contributions.

Abstract

Treating baryons as quark + interacting-diquark bound states, a symmetry-preserving formulation of a vector$\,\times\,$vector contact interaction (SCI) is used to deliver an extensive, coherent set of predictions for $\Lambda, \Sigma^0$ baryon unpolarised and polarised distribution functions (DFs) -- valence, glue, and four-flavour separated sea -- and compare them with those of a like-structured nucleon. $\Lambda, \Sigma^0$ baryons are strangeness negative-one isospin partners within the SU$(3)$-flavour baryon octet. This makes such structural comparisons significant. The study reveals impacts of diquark correlations and SU$(3)$-flavour symmetry breaking on $\Lambda$, $\Sigma^0$ structure functions, some of which are significant. For instance, were it not for the presence of axialvector diquarks in the $\Sigma^0$ at the hadron scale, the $s$ quark could carry none of the $\Sigma^0$ spin. The discussion canvasses issues that include helicity retention in hard scattering processes; the sign and size of polarised gluon DFs; and the origin and decomposition of baryon spins. Interpreted judiciously, the SCI analysis delivers an insightful explanation of baryon structure as expressed in DFs.