Unquenched quark model for baryons: magnetic moments, spins and orbital angular momenta

TL;DR

This paper introduces an unquenched quark model for baryons that explicitly includes quark-antiquark pairs, revealing their significant impact on orbital angular momentum contributions to baryon spins, especially in the proton and Lambda hyperon.

Contribution

The model explicitly incorporates quark-antiquark pairs in baryons, allowing detailed study of their effects on magnetic moments and angular momentum contributions.

Findings

Quark-antiquark pairs do not alter baryon magnetic moments.

Orbital angular momentum significantly contributes to the proton and Lambda hyperon spins.

The approach is applicable to any initial baryon and quark flavor.

Abstract

We present an unquenched quark model for baryons in which the effects of the quark-antiquark pairs (up, down and strange) are taken into account in an explicit form via a microscopic, QCD-inspired, quark-antiquark creation mechanism. In the present approach, the contribution of the quark-antiquark pairs can be studied for any inital baryon and for any flavor of the pairs. It is shown that, while the inclusion of quark-antiquark pairs does not affect the baryon magnetic moments, it leads to a sizeable contribution of the orbital angular momentum to the spin of the proton and the Lambda hyperon.