Exploring the multiplicity dependence of the flavor hierarchy for hadron productions in high energy pp collisions

Abstract

In this work, we perform a systematic study on the multiplicity dependence of hadron productions at mid-rapidity ($|y|<0.5$), ranging from the light to the charm sector in pp collisions at $\sqrt{s}=13$ TeV. This study utilizes a multi-phase transport model (AMPT) coupled with PYTHIA8 initial conditions. We have investigated the baryon to meson ratios as well as the strange to non-strange meson ratios varying with the charged particle density. By tuning the coalescence parameters, the AMPT model provides a reasonable description to the experimental data for inclusive productions of both light and charm hadrons, comparable to the string fragmentation model calculations with color reconnection effects. Additionally, we have analyzed the relative production of hadrons by examining self-normalized particle ratios as a function of the charged hadron density. Our findings suggest that parton evolution effects and the coalescence hadronization process in AMPT model lead to a strong flavor hierarchy in the multiplicity dependence of the baryon to meson ratio. Furthermore, our investigation on the $p_T$ differential double ratio of baryon to meson fraction between high and low multiplicity events indicates distinct modifications to the flavor associated baryon to meson ratio $p_T$ shape in high multiplicity events when comparing the coalescence hadronization model to the color reconnection model. These observations highlight the importance of understanding the hadronization process in high-energy proton-proton collisions through a comprehensive multiplicity dependent multi-flavor analysis.