Recent developments in the constituent quark model including quark-antiquark pairs

TL;DR

This paper introduces an advanced unquenched quark model for baryons that explicitly incorporates quark-antiquark pairs, revealing significant effects on proton spin and extending previous flux-tube breaking models.

Contribution

It develops a microscopic, QCD-inspired formalism for unquenched baryon models that explicitly includes quark-antiquark pairs of any flavor, extending prior flux-tube breaking approaches.

Findings

Quark-antiquark pairs significantly contribute to orbital angular momentum in the proton.

The model allows studying any initial baryon and q anti-q flavor.

Explicit inclusion of pairs affects baryon properties and spin structure.

Abstract

We present the formalism for a new generation of unquenched quark models for baryons in which the effects of quark-antiquark pairs (u anti-u, d anti-d and s anti-s) are taken into account in an explicit form via a microscopic, QCD-inspired, quark-antiquark creation mechaniscm. The present approach is an extension of the flux-tube breaking model of Geiger and Isgur in which now the contributions of quark-antiquark pairs an be studied for any initial baryon and for any flavor of the q anti-q pair. It is shown that the inclusion of q anti-q paris leads to a large contribution of orbital angular momentum to the proton spin.