't Hooft模型中π介子的奇异-反奇异与粲-反粲不对称性
Strange-antistrange and charm-anticharm asymmetries of pion in 't Hooft model
AI总结：
本文在't Hooft模型中研究第一激发π介子的奇异-反奇异和粲-反粲不对称性，发现其可达百分之几水平，并揭示介子云模型在粲-反粲不对称性上与严格方法存在严重分歧。
摘要：
作为我们先前工作[S. Hu et al., Phys. Rev. D 108 (2023) 9, 094040]的续篇，我们研究了轻味介子部分子分布函数（PDFs）中的奇异-反奇异和粲-反粲不对称性，以't Hooft模型（即二维时空、颜色数取无穷大的QCD）中的第一激发π介子为例。作为${\cal O}(1/N_c)$阶效应，内禀奇异成分必然来源于轻味介子的更高Fock分量，这需要引入无穷多个$K$和$\overline{K}$介子塔。数值研究表明，当$m_u/m_d=1/2$时，第一激发$π^-$的$s$-$\bar{s}$和$c$-$\bar{c}$不对称性可以达到百分之几的水平。虽然介子云模型（MCM）预言的$s$-$\bar{s}$不对称性与严格方法大体一致，但两种方法在$c$-$\bar{c}$不对称性上存在严重分歧。
英文摘要：
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 $π^-$ 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.
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