Determination of Fragmentation Functions from Charge Asymmetries in Hadron Production

Abstract

We propose a novel method for extracting non-singlet (NS) fragmentation functions (FFs) of light charged hadrons from charge asymmetries measured in hadron fragmentation, using data from both single-inclusive electron-positron annihilation and semi-inclusive deep-inelastic scattering processes. We determine the NS FFs for pions and kaons at next-to-next-to-leading order in Quantum Chromodynamics, including a comprehensive uncertainty analysis. The extracted FFs reveal a scaling index of about 0.7 at large momentum fractions and low energy scales, a strangeness suppression factor of about 0.5, and universality in fragmentation of light mesons. Our findings provide a valuable benchmark for testing non-perturbative QCD models and Monte Carlo event generators, and serve as crucial input for future electron-ion colliders.

Figures (8)

• Figure 1: The global and individual $\chi^2$ variations as a function of the $\beta$ parameter. The best-fit $\chi^2$ values from alternative fits and several models are also shown.
• Figure 2: The NS FF $D_{u^-}^{\pi^+}$ at a scale of 1.3 GeV, as a function of $z$ from our nominal and alternative fits, compared with predictions from the Field-Feynman model, MC generators, and previous FF determination.
• Figure 3: Ratios of the NS FFs of kaons and pions at a scale of 1.3 GeV, from our nominal and alternative fits, compared with predictions from the Field-Feynman model, MC generators, and previous FF determinations.
• Figure 4: Comparison of SLD measurements of kaon charge asymmetry in the light-quark tagged hemisphere with theoretical predictions at NNLO based on FFs from this fit and from previous determinations, as well as predictions from MC event generators.
• Figure 5: Comparisons of experimental data and predictions from nominal fit and fit fixing $\beta=2$ for COMPASS measurements of pion multiplicity difference with iso-scalar target. Scale uncertainties are shown in shaded bands and estimated by varying $\mu_R/{\mu_{R,0}}=\mu_F/{\mu_{F,0}}=\mu_D/\mu_{D,0}=\{1/2,1,2\}$ and taking the envelope. Hessian uncertainties are evaluated by the Hessian method. Experimental uncertainties shown are quadratic sum of statistical and uncorrelated systematic uncertainties. Each panel represents different kinematic regions in $x$ and $y$.