Hadrons from Coalescence plus Fragmentation in AA collisions from RHIC to LHC energy

TL;DR

This paper models hadron production in heavy-ion collisions across RHIC and LHC energies using coalescence and fragmentation, successfully predicting spectra and ratios, and analyzing discrepancies with experimental data.

Contribution

It extends a coalescence plus fragmentation model to include resonance decays, accurately predicting hadron spectra and ratios from RHIC to LHC energies without changing parameters.

Findings

Model predicts baryon-to-meson ratios reaching unity at ~3 GeV

Discrepancy in yield around 6 GeV suggests fragmentation functions are too flat

p/φ ratio remains constant up to 4 GeV before decreasing

Abstract

In a coalescence plus independent fragmentation approach we calculate the $p_T$ spectra of the main hadrons: $\pi, K, p, \bar p, \Lambda, \phi$ in a wide range of transverse momentum from low $p_T$ up to about 10 GeV. The approach in its main features was developed several years ago at RHIC energy. Augmenting the model with the inclusion of some more main resonance decays, we show that the approach correctly predicts the evolution of the $p_T$ spectra from RHIC to LHC energy and in particular the baryon-to-meson ratios $p/\pi,\bar p/\pi,\Lambda/K$ that reach a value of the order of unit at $p_T \sim 3\, \rm GeV$. This is achieved without any change of the coalescence parameters. The more recent availability of experimental data up to $p_T \sim 10\rm\, GeV$ for $\Lambda$ spectrum as well as for $p/\pi$ and $\Lambda/K$ shows some lack of yield in a limited $p_T$ range around 6 GeV. This indicates that the baryons $p_T$ spectra from AKK fragmentation functions are too flat at $p_T\lesssim 8 \,\rm GeV$. We also show that in a coalescence plus fragmentation approach one predicts a nearly $p_T$ independent $p/\phi$ ratio up to $p_T \sim 4 \rm\, GeV$ followed by a significant decrease at higher $p_T$. Such a behavior is driven by a similar radial flow effect at $p_T< 2 \,\rm GeV$ and the dominance of fragmentation for $\phi$ at larger $p_T$.