Perturbative and nonperturbative contributions to the strange quark asymmetry in the nucleon

TL;DR

This paper investigates the strange-antistrange quark asymmetry in the nucleon by combining nonperturbative and perturbative mechanisms, revealing that perturbative effects dominate at small x and suggesting optimal experimental detection regions.

Contribution

It provides a comprehensive calculation of the strange-antistrange asymmetry considering both nonperturbative and perturbative effects, highlighting the potential for multiple nodes in the asymmetry.

Findings

Perturbative contributions are larger than nonperturbative ones in magnitude.

The asymmetry is most detectable in the region 0.02 < x < 0.03.

The asymmetry may have multiple nodes, affecting global parton distribution analyses.

Abstract

There are two mechanisms for the generation of an asymmetry between the strange and anti-strange quark distributions in the nucleon: nonperturbative contributions originating from nucleons fluctuating into virtual baryon-meson pairs such as $\Lambda K$ and $\Sigma K$, and perturbative contributions arising from gluons splitting into strange and anti-strange quark pairs. While the nonperturbative contributions are dominant in the large-$x$ region, the perturbative contributions are more significant in the small-$x$ region. We calculate this asymmetry taking into account both nonperturbative and perturbative contributions, thus giving a more accurate evaluation of this asymmetry over the whole domain of $x$. We find that the perturbative contributions are generally a few times larger in magnitude than the nonperturbative contributions, which suggests that the best region to detect this asymmetry experimentally is in the region $0.02 < x < 0.03$. We find that the asymmetry may have more than one node, which is an effect that should be taken into account, e.g. for parameterizations of the strange and anti-strange quark distributions used in global analysis of parton distributions.