AKK Update: Improvements from New Theoretical Input and Experimental Data

TL;DR

This paper enhances the AKK fragmentation function extraction by integrating new experimental data, applying hadron mass corrections, and implementing large x resummation, leading to improved fits and more accurate modeling of hadron production.

Contribution

It introduces a comprehensive update to the AKK fragmentation functions including new data, mass effects, and resummation techniques, advancing the precision of hadronization models.

Findings

Improved fit quality with reduced chi-squared values.

Fitted hadron masses closely match physical values.

Enhanced constraints on valence quark fragmentation functions.

Abstract

We perform a number of improvements to the previous AKK extraction of fragmentation functions for $\pi^\pm$, $K^\pm$, $p/\bar{p}$, $K_S^0$ and $\Lambda/\bar{\Lambda}$ particles at next-to-leading order. Inclusive hadron production measurements from $pp(\bar{p})$ reactions at BRAHMS, CDF, PHENIX and STAR are added to the data sample. We use the charge-sign asymmetry of the produced hadrons in $pp$ reactions to constrain the valence quark fragmentations. Data from $e^+ e^-$ reactions in regions of smaller $x$ and lower $\sqrt{s}$ are added. Hadron mass effects are treated for all observables and, for each particle, the hadron mass used for the description of the $e^+ e^-$ reaction is fitted. The baryons' fitted masses are found to be only around 1% above their true masses, while the values of the mesons' fitted masses have the correct order of magnitude. Large $x$ resummation is applied in the coefficient functions of the $e^+ e^-$ reactions, and also in the evolution of the fragmentation functions, which in most cases results in a significant reduction of the minimized $\chi^2$. To further exploit the data, all published normalization errors are incorporated via a correlation matrix.