Uncertainties of Cosmic Ray Spectra and Detectability of Antiproton mSUGRA Contributions With PAMELA

TL;DR

This work quantifies uncertainties in cosmic-ray secondary spectra arising from Milky Way propagation and cross sections using Galprop constrained by B/C data, and then evaluates PAMELA's ability to detect a neutralino annihilation–driven antiproton component within the mSUGRA framework. It combines ISASUGRA for SUSY spectra, DarkSUSY for annihilation physics, Pythia for yields, and a clumpy-halo model to boost the SUSY signal, all propagated with a DC model consistent with Galactic convection. The authors find that PAMELA could disentangle a supersymmetric antiproton component for modest clumpiness factors (roughly $fd$ of order 1–10) in many parameter regions, with more stringent requirements in some backgrounds, and highlight the importance of DM halo structure and cross-section uncertainties. Overall, the study underscores PAMELA's potential to constrain or reveal supersymmetric DM signals while emphasizing the need for accurate propagation, cross sections, and halo modeling to interpret the data.

Abstract

We studied the variation of $e^+$ and $\bar p$ top of the atmosphere spectra due to the parameters uncertainties of the Milky Way geometry, propagation models and cross sections. We used the B/C data and Galprop code for the propagation analysis. We also derived the uncertainty bands for subFe/Fe ratio, H and He. Finally, we considered a neutralino induced component in the antiproton flux in the mSUGRA framework. PAMELA expectations for positrons and antiprotons are calculated. We studied in details the possibility of disentanglement of an eventual signal component in the antiproton spectra in a clumpy halo scenario: minimal values of clumpiness factors necessary to disentangle the signal from the background without violating the quality of the antiproton data fit are found. There are also given examples of total spectra in comparison with existing experimental data and an example of PAMELA prediction for the total spectra. The main result of this work is that for the diffusion and convection background model PAMELA will be able to disentangle an eventual supersymmetric signal even for small clumpiness factors.

Figures (22)

• Figure 1: Propagation parameters uncertainty for B/C ratio: for the DR model it is given with solid lines around the best fit (dashed line), while for the DC model it is given with dotted lines around the best fit (dashed line). For DRB model we give the best fit (dashed line). For the complete list of the experimental data see expBC.
• Figure 2: Upper and lower bounds of positron spectra due to the uncertainties of the propagation parameters are represented with solid lines for the DC model, with dashed lines for the DR model and with dotted lines for the DRB model. The DR and DRB model uncertainties are very similar, but there is a slight improvement of the fit in the low energy part of the spectra in the case of DRB model. On the other hand, around the maximum the DRB model overestimates the data slightly more than the DR model. Experimental data are taken from expe.
• Figure 3: Upper and lower bounds of the antiproton spectra due to the uncertainties of the propagation parameters for the DC model (solid lines) and DRB model (dotted lines). The propagation parameters uncertainties for the DR model are almost the same as those of the DRB model (see the discussion later in the text), so we are not presenting them here to avoid the confusion. Experimental data are taken from exppbar.
• Figure 4: Ratio (Sc+Ti+V)/Fe that corresponds to the propagation parameters that give the best fits of B/C data for the DC model given with dashed line. It is inside the corresponding uncertainty band also given with dashed lines. The ratio for the DR model is given with dotted line and it is inside the uncertainty given with solid lines, while for DRB model is given with larger-step dashed line without the uncertainty band around. Experimental data are taken from expsubFe/Fe.
• Figure 5: Top of the atmosphere spectra of electrons that correspond to the parameters of the best B/C fit are the lower curves: for the DC model they are given with solid line, for the DR model with dashed line and for DRB model with dotted line. The local interstellar spectra are the upper curves; the three models are represented with the same types of lines. Experimental data are taken from expe.