I use a direct method to extract the longitudinal structure function in the next-to-leading order approximation with respect to the number of active flavor from the parametrization of parton distributions. The contribution of charm and bottom quarks corresponding to the gluon distributions (i.e., \({{G}_{{{{n}_{f}} = 3}}}\)(x, Q²) and \({{G}_{{{{n}_{f}} = 5}}}\)(x, Q²)) is considered. I compare the obtained longitudinal structure function at n_f = 4 with the H1 data [Eur. Phys. J. C 74, 2814 (2014) and Eur. Phys. J. C 71, 1579 (2011)] and the result L. P. Kaptari et al. [Phys. Rev. D 99, 096019 (2019)] which is based on the Mellin transforms. These calculations compared with the results from CT18 [Phys. Rev. D 103, 014013 (2021)] parametrization model. The nonlinear effects on the gluon distribution improve the behavior of the longitudinal structure function in comparison with the H1 data and CT18 at low values of Q².

我使用直接方法从 parton 分布的参数化中提取关于活跃风味数量的次前序近似的纵向结构函数。对应于胶子分布的魅力和底夸克的贡献（即，\({{G}_{{{{{n}_{f}} = 3}}}\) ( x , Q ² ) 和\({ {G}_{{{{n}_{f}} = 5}}}\) ( x , Q ² )) 被考虑。我将在n _f = 4处获得的纵向结构函数与 H1 数据 [Eur. 物理。J. C  74 , 2814 (2014) 和 Eur。物理。J.C 71, 1579 (2011)] 和结果 LP Kaptari 等。[物理。Rev. D 99 , 096019 (2019)] 基于梅林变换。这些计算与 CT18 [Phys. Rev. D 103 , 014013 (2021)] 参数化模型。与低Q ²值下的 H1 数据和 CT18 相比，胶子分布的非线性效应改善了纵向结构函数的行为。