Impact of QCD uncertainties on antiproton spectra from dark-matter annihilation

TL;DR

This paper evaluates how quantum chromodynamics (QCD) uncertainties influence the predicted antiproton spectra from dark matter annihilation, highlighting their significance in interpreting experimental data like AMS-02.

Contribution

It quantifies the impact of QCD uncertainties on dark matter parameter estimates and provides tools for incorporating these uncertainties in future analyses.

Findings

QCD uncertainties can alter dark matter mass estimates by up to 14%.

The impact on annihilation cross section is up to 10%.

QCD uncertainties are more significant than cosmic-ray propagation model variations.

Abstract

Dark-matter particles that annihilate or decay can undergo complex sequences of processes, including strong and electromagnetic radiation, hadronisation, and hadron decays, before particles that are stable on astrophysical time scales are produced. Antiprotons produced in this way may leave footprints in experiments such as AMS--02. Several groups have reported an excess of events in the antiproton flux in the rigidity range of $10$--$20$ GV. However, the theoretical modeling of baryon production is not straightforward and relies in part on phenomenological models in Monte Carlo event generators. In this work, we assess the impact of QCD uncertainties on the spectra of antiprotons from dark-matter annihilation. As a proof-of-principle, we show that for a two-parameter model that depends only on the thermally-averaged annihilation cross section ($\langle \sigma v \rangle$) and the dark-matter mass ($M_\chi$), QCD uncertainties can affect the best-fit mass by up to $\sim 14 \%$ (with large uncertainties for large DM masses), depending on the choice of $M_\chi$ and the annihilation channel ($b\bar{b}$ or $W^+ W^-$), and $\langle \sigma v \rangle$ by up to $\sim 10\%$. For comparison, changes to the underlying diffusion parameters are found to be within $1\%$--$5\%$, and the results are also quite resilient to the choice of cosmic-ray propagation model. These findings indicate that QCD uncertainties need to be included in future DM analyses. To facilitate full-fledged analyses, we provide the spectra in tabulated form including QCD uncertainties and code snippets to perform mass interpolations and quick DM fits. The code can be found in this \href{https://github.com/ajueid/qcd-dm.github.io.git}{github} repository.