Fragmentation Functions for Light Charged Hadrons with Complete Quark Flavour Separation

TL;DR

This work delivers a new set of next-to-leading order fragmentation functions for charged pions, kaons, and protons with complete light-quark flavour separation, derived from e+e- annihilation data and OPAL tagging probabilities. It employs a factorization framework with DGLAP evolution, solved efficiently in Mellin space, and fits a simple initial fragmentation-function form to constrain both the FFs and the strong coupling. The AKK 2005 FFs show improved description of flavor-separated kaon production and consistent predictions for hadron production in hadronic collisions, with the strong coupling constant at the Z pole extracted as a cross-check. The results provide a publicly available tool for precise hadron production predictions at current and future colliders, including LHC-era phenomenology.

Abstract

We present new sets of next-to-leading order fragmentation functions describing the production of charged pions, kaons and protons from the gluon and from each of the quarks, obtained by fitting to all relevant data sets from e+ e- annihilation. The individual light quark flavour fragmentation functions are obtained phenomenologically for the first time by including in the data the light quark tagging probabilities obtained by the OPAL Collaboration.

Figures (10)

• Figure 1: Light quark probabilities $\eta^h_a(x_p,s)$ at $\sqrt{s}=91.2$ GeV. The dashed curves are calculated using the FFs obtained in Ref. Kniehl:2000fe, the dotted curves are calculated from the $(x,M_f^2)$ grid of FFs obtained from the analysis of Ref. Kretzer:2000yf (in which no $p/\overline{p}$ FFs are obtained), and the solid curves are calculated using the FFs obtained in the analysis of this paper. The corresponding measured OPAL probabilites of Ref. Abbiendi:1999ry are also shown.
• Figure 2: As in Fig. \ref{['fig1']}, but for the heavy quark probabilities.
• Figure 3: Normalized differential cross section of inclusive hadron production. The curves are calculated from the FFs obtained in our analysis, at 29 (dashed line) and 91.2 (solid line) GeV. The upmost, second, third and lowest curves refer to charged hadrons, $\pi^{\pm}$, $K^{\pm}$ and $p/\overline{p}$ respectively. The differential cross section for the charged hadron curve was calculated by taking the sum of the differential cross sections for the three lightest charged hadrons. The ALEPH Buskulic:1994ft, DELPHI Abreu:1998vq, OPAL Ackerstaff:1998hz, SLD Abe:1998zs and TPC Aihara:1988fc data sets are shown. The charged hadron data are shown just for comparison, but were not used in the fit. Each curve or pair of curves and the corresponding data is rescaled relative to the nearest upper one by a factor of 1/5.
• Figure 4: As in Fig. \ref{['fig2']}, but for the light quark tagged cross sections. The ALEPH Buskulic:1994ft, DELPHI Abreu:1998vq, OPAL Ackerstaff:1998hz, SLD Abe:1998zs and TPC Aihara:1986mv data sets are shown. The charged hadron data are shown just for comparison, but were not used in the fit.
• Figure 5: As in Fig. \ref{['fig2']}, but for the $c$ quark tagged cross sections. The ALEPH Buskulic:1994ft, OPAL Ackerstaff:1998hz , SLD Abe:1998zs and TPC Aihara:1986mv data sets are shown. The two SLD data points at $x=0.654$ are for the pion (upper) and proton (lower). The charged hadron data are shown just for comparison, but were not used in the fit.