Description of Charged-Particle Multiplicity Distributions in High-Energy Proton-Proton Collisions Based on a Two-Component Model and Examination of Parton Distribution Functions

High-energy proton-proton collisions provide an important probe of small-x gluon dynamics in quantum chromodynamics. In this work, charged-particle pseudorapidity distributions in high-energy pp collisions are studied within a two-component model. The central component is described by gluon-gluon fusion using unintegrated gluon distributions constructed with the Kimber-Martin-Ryskin prescription, while the fragmentation component is modeled through quark recombination with collinear parton distributions. The integrated PDFs are evolved using the modified DGLAP equations including nonlinear gluon-recombination corrections. The calculated (1/N ev ) dN ch /dη distributions are compared with ATLAS data at [Formula: see text] = 0.9, 2.36, 7, and 13 TeV. After normalization at midrapidity, the model reproduces the main features of the measured distributions, with gluon fusion dominating the central rapidity region. Comparisons with CT18, MSHT20, NNPDF, HERAPDF2.0, and GRV98 PDFs show that the pseudorapidity shape is sensitive to the small-x behavior of the gluon distribution. The results suggest that charged-particle pseudorapidity distributions can serve as a useful phenomenological test of small-x gluon PDFs within two-component models.