Testing of Pythia modes to study identified particle production in high-multiplicity pp collisions at $\mathbf{\sqrt{s}}$ = 7 TeV

Abstract

This study presents a comprehensive analysis of particle production in proton-proton ($pp$) collisions at $\sqrt{s}$ = 7 TeV using Pythia~8 event generator. We investigate the transverse momentum $p_T$ spectra of light charged hadrons ($π^\pm$, $K^\pm$ and $p(\bar p)$), their yield ratios ($π^-/π^+$, $K^-/K^+$ and $\bar{p}/p$), and $p_T$-differential ratios ($(K^++K^-)/(π^++π^-)$, $(\overline{p}+p)/(π^++π^-)$) and mean transverse momentum ($\langle p_\mathrm{T} \rangle$). Our analysis employs various Pythia~8 tunes (Simple, Vincia, and Dire) to explore the impact of different model configurations on particle production. We optimize a key parameter ($p_\mathrm{T}HatMin$) within each tune to achieve the best agreement between the simulated \ppt spectra and those measured by the CMS collaboration. Interestingly, we find that the optimal values for $p_\mathrm{T}HatMin$ differ between hadron species, potentially reflecting the influence of particle mass on production mechanisms. It is not possible to simultaneously and qualitatively describe both, the strangeness enhancement and collectivity in $pp$ collisions from \pythia~8. Further investigation such as final-state effects such as color ropes or junctions may require to explain these effects. These types of studies help us identify limitations in current models and refine their parameters to better explain experimental observations.