CERN Accelerating science

The wealth of data collected by the CERN LHC during Run 1 (2009–2013) data taking period, and the unprecedented center-of-mass ($\sqrt{s}$) energies reached during Run 2 (2015–2018) made it possible to study identified hadron production in new kinematic regimes. Measuring identified particle production over wide kinematic ranges is considered an informative probe of strong interactions at high energies. This Ph.D. thesis mainly focuses on the measurements of single-inclusive particle transverse momentum ($_{pT}$) spectra of charged pions ($\pi$$^{\pm}$), kaons (K$^{±}$), and (anti)protons (p($\bar{p}$)) up to $_{pT}$ = 20GeV/$c$. Particle production is studied at mid-rapidity in minimum bias inelastic proton-proton(pp) collisions as a function of $\sqrt{s}$ and in non-single diffractive (NSD) proton-lead (p–Pb) collisions as a function of event charged-particle multiplicity measured at forward rapidity using the ALICE detector at the CERN LHC. The increase of $\sqrt{s}$ reached at the LHC opens up domains in Bjorken-$x$ where the contribution of gluons to inclusive hadron production becomes dominant. Therefore,identified particle spectra at the top LHC energy in pp collisions provide new constraints on gluon fragmentation in theoretical calculations and gives input to tune the modeling of several contributions in state-of-the-art Monte Carlo (MC) event generators. Also, in this kinematic regime, the nuclear modification to hadronic structure is expected to be sizable. By using a proton instead of a heavy nucleus as a projectile, measurements of p–Pb collisions have unique sensitivity to the initial-state nuclear wave function. High-$_{pT}$ identified particle spectra measured in p–Pb collisions provide new constraints on the nuclear-modified parton distribution functions (nPDFs) and the flavor dependence of sea-quark nPDFs, which are key inputs in interpreting a large amount of experimental data like deuterium-gold and deep inelastic scattering.