Strange-antistrange and charm-anticharm asymmetries of pion in 't Hooft model

TL;DR

This paper investigates strange-antistrange and charm-anticharm asymmetries in the first excited pion's parton distribution functions within the 't Hooft model, revealing significant asymmetries and comparing different theoretical approaches.

Contribution

It provides a detailed analysis of quark-antiquark asymmetries in a light meson using the 't Hooft model, highlighting the role of higher Fock states and comparing with meson cloud model predictions.

Findings

s-anti-s and c-anti-c asymmetries can reach percent levels

Agreement between 't Hooft model and meson cloud model for s-anti-s asymmetry

Discrepancy between models for c-anti-c asymmetry

Abstract

As a sequel of our preceding work [S. Hu et al., Phys. Rev. D 108 (2023) 9, 094040], we investigate the strange-antistrange and charm-anticharm asymmetries in the parton distribution functions (PDFs) of a light flavored meson, exemplified by the first excited pion in the 't Hooft model, {\it viz.}, QCD in two spacetime dimensions with infinite number of colors. Counted as an ${\cal O}(1/N_c)$ effect, the intrinsic strange content necessarily originates from the higher Fock component of the light flavored meson, which entails infinite towers of $K$ and $\overline{K}$ mesons. Numerical studies reveal that, with $m_u/m_d=1/2$, the $s$-$\bar{s}$ and $c$-$\bar{c}$ asymmetries of the first excited $\pi^-$ can reach per cents level. While the $s$-$\bar{s}$ asymmetry predicted from the meson cloud model (MCM) grossly align with the rigorous approach, there exists severe discrepancy between two approaches on the $c$-$\bar{c}$ asymmetry.