Speaker
Description
We present predictions from phenomenological models to study the transverse momentum spectra of identified hadrons in Au+Au collisions at a center-of-mass energy of 7.7 GeV, as measured by the STAR detector at the Relativistic Heavy Ion Collider. This analysis evaluates the performance of Monte Carlo models Pythia8.3 and EPOS (EPOS4 and EPOSLHC) by comparing their predictions with experimental data. The transverse momentum spectra of π±, K±, and (anti-)protons at mid-rapidity (|y| < 0.1) are examined across nine centrality classes.
The EPOS4 model demonstrates good agreement with data for π±, K±, and anti-protons across most centrality classes. However, its accuracy declines in peripheral collisions, particularly underestimating protons at high pT due to reduced interaction volume and limited re-scattering. Pythia8.3 tends to overestimate pion spectra and misrepresent kaons and (anti-)protons depending on centrality. In contrast, EPOSLHC aligns better with experimental data for π± and anti-protons at higher pT, though it underestimates kaons and protons in most centrality classes. Suppression at high pT in EPOSLHC arises from collective flow, which has minimal impact on high-pT particles, while EPOS4 exhibits suppression in (anti-)protons due to baryon-antibaryon annihilation. None of the models accurately reproduce the data for the most peripheral centrality class. Additionally, the extracted freeze-out parameters indicate that the effective temperature increases, while the non-extensive parameter decreases with centrality, suggesting greater system excitation and faster thermal equilibration in more central collisions.
This study provides insights into the strengths and limitations of these models, commonly employed in cosmic ray Monte Carlo (CRMC) simulations, describing hadron spectra and highlighting key physics mechanisms influencing particle production in heavy-ion collisions and cosmic ray interactions.
