Abstract
Recent cosmic-ray (CR) studies have claimed the possibility of an excess on the antiproton flux over the predicted models at around 10 GeV, which can be the signature of dark matter annihilating into hadronic final states that subsequently form antiprotons. However, this excess is subject to many uncertainties related to the evaluation of the antiproton spectrum produced from spallation interactions of CRs. In this work, we implement a combined Markov-Chain Monte Carlo analysis of the secondary ratios of B, Be and Li and the antiproton-to-proton ratio (p̅/p), while also including nuisance parameters to consider the uncertainties related to the spallation cross sections. This study allows us to constrain the Galactic halo height and the rest of propagation parameters, evaluate the impact of cross sections uncertainties in the determination of the antiproton spectrum and test the origin of the excess of antiprotons. In this way, we provide a set of propagation parameters and scale factors for renormalizing the cross sections parametrizations that allow us to reproduce all the ratios of B, Be, Li and p̅ simultaneously.We show that the energy dependence of the p̅/p ratio is compatible with a pure secondary origin. In particular, we find that the energy dependence of the evaluated p̅/p spectrum matches that observed from AMS-02 data at energies above ∼3 GeV, although there is still a constant ∼10% excess of p̅ over our prediction. We discuss that this discrepancy is more likely explained from a ∼10% scaling in the cross sections of antiproton production, rather than a component of dark matter leading to antiprotons. In particular, we find that the best-fit WIMP mass (∼300 GeV) needed to explain the discrepancy lies above the constraints from most indirect searches of dark matter and the resultant fit is poorer than with a cross sections scaling.
Highlights
We show that the energy dependence of the p/p ratio is compatible with a pure secondary origin
We investigate the antiproton spectrum produced from CR collisions with the interstellar gas by employing an analysis that combines the p/p spectrum with the flux ratios of secondary CRs B, Be and Li to constrain the propagation parameters and accounting for systematic uncertainties in the cross sections parametrizations of production of these secondary nuclei
We have studied the diffuse p/p spectrum produced in CR interactions with the interstellar gas
Summary
We show that the energy dependence of the p/p ratio is compatible with a pure secondary origin. We find that the energy dependence of the evaluated p/p spectrum matches the AMS-02 data at energies above ∼ 3 GeV, there is still a nearly constant ∼ 10% excess of pover our prediction We discuss that this discrepancy is more likely explained from a ∼ 10% scaling in the cross sections of antiproton production, rather than a component of dark matter leading to antiprotons. The uncertainties related to the cross sections for secondary CR production are high (> 20%), which leads to large uncertainties in the determination of the diffusion coefficient [26,27,28], since this is usually determined from the flux ratios of secondary-to-primary CRs. correlated errors in the AMS-02 data seem to lead to looser constraints in the determination of the propagation parameters, reducing the significance of the antiproton excess even below 1σ level and implying that current models are consistent with the AMS-02 antiproton data [29, 30]. Non-annihilation inelastic interactions of antiprotons with interstellar protons yield an extra source of lower energy antiprotons, which we refer to as a “tertiary” source of antiprotons, but this represents a very subdominant contribution to the total spectrum of antiprotons [32] so that the uncertainties related to this tertiary antiprotons is negligible for the evaluation of the antiproton spectrum
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