  In dark-matter annihilation channels to hadronic final states, stable
particles -- such as positrons, photons, antiprotons, and antineutrinos -- are
produced via complex sequences of phenomena including QED/QCD radiation,
hadronisation, and hadron decays. These processes are normally modelled by
Monte Carlo event generators whose limited accuracy imply intrinsic QCD
uncertainties on the predictions for indirect-detection experiments like
Fermi-LAT, Pamela, IceCube or AMS-02. In this article, we perform a complete
analysis of QCD uncertainties in antimatter spectra from dark-matter
annihilation, based on parametric variations of the Pythia 8 event generator.
After performing several retunings of light-quark fragmentation functions, we
define a set of variations that span a conservative estimate of the QCD
uncertainties. We estimate the effects on antimatter spectra for various
annihilation channels and final-state particle species, and discuss their
impact on fitted values for the dark-matter mass and thermally-averaged
annihilation cross section. We find dramatic impacts which can go up to
$\mathcal{O}(40)$ GeV for uncertainties on the dark-matter mass and up to
$\mathcal{O}(10\%)$ for the annihilation cross section. We provide the spectra
in tabulated form including QCD uncertainties and code snippets to perform fast
dark-matter fits, in this https://github.com/ajueid/qcd-dm.github.io.git
repository.
