Can STAR $p+p$ data help constrain fragmentation functions for strange hadrons

TL;DR

This paper uses STAR's $p+p$ collision data at 200 GeV to test and constrain fragmentation functions for strange hadrons, revealing limitations of pQCD models and suggesting additional non-perturbative effects.

Contribution

It demonstrates that STAR data can refine fragmentation functions, especially for gluons, and highlights discrepancies with pQCD predictions at intermediate transverse momentum.

Findings

Tuned PYTHIA describes strange particle spectra.

STAR Lambda data constrains gluon fragmentation functions.

pQCD fails to explain baryon-to-meson ratio enhancement.

Abstract

STAR has measured a variety of strange particle species in $p+p$ collisions at $\sqrt{s}$=200 GeV. These high statistics data are ideal for comparing to existing leading- and next-to-leading order perturbative QCD (pQCD) models. Leading-order (LO) models such as PYTHIA need to be tuned to describe identified strange particle data from STAR. We show that tuned PYTHIA can also describe the pt-spectra of strange resonances. More rigorous Next-to-Leading order pQCD calculations using parameterized fragmentation functions for quarks and gluons will also be compared to STAR data. The OPAL experiment has recently released $e^{+}e^{-}$ data from light quark flavor tagged analyses allowing for the first time to make precise parameterizations of light flavor separated fragmentation function. We show that our Lambda data put a more stringent constraint on the gluon fragmentation function than $e^{+}e^{-}$ data. Furthermore we show that pQCD fails to describe the observed enhancement of baryon-to-meson ratio at intermediate pt (2-6 GeV/c), which may be a first indication of other, non-perturbative mechanisms at play in $p+p$ collisions at that momentum.