In high-energy proton-proton (pp) collisions, the transverse momentum (pT) spectrum of produced particles exhibits two characteristic regimes: a soft region at low pT, commonly described by statistical models, and a hard region at high pT, associated with perturbative Quantum Chromodynamics.

The pT region where the soft description begins to break down and the transition toward hard processes takes place remains an important subject of study [1-4]. This work aims to characterize this transition across different multiplicity classes in pp collisions at $\sqrt{s} = 13$ TeV simulated with Pythia 8.

We investigate how jet activity influences the soft-hard transition and whether this behavior changes across different event multiplicities. The aim is to characterize the momentum region where the soft description begins to lose validity.

[1] T.A. Trainor, Comparing the PYTHIA Monte Carlo to a two-component (soft + hard) model of hadron production in high-energy pp collisions. Int. J. Mod. Phys. E 28(04), 1950023 (2019).

[2] D. R. Herrera, J.R. Alvarado Garcıa, A. Fernandez Tellez, J.E. Ramirez, C. Pajares, Entropy and heat capacity of the transverse momentum distribution for pp collisions at RHIC and LHC energies. Phys. Rev. C 109(3), 034915 (2024).

[3] G. Bíró, L. Serkin, G. Paić, and G. G. Barnaföldi, “Investigating the soft and hard limits in transverse momentum spectra in pp collisions,” Eur. Phys. J. Spec. Top. (2025).

[4] G. Bíró, G. Paić, L. Serkin, and G. G. Barnaföldi, “Revisiting the soft-hard separation in the transverse momentum spectra of pp collisions,” Eur. Phys. J. C 86, 810 (2026).