PAMELA and AMS-02e+ande−spectra are reproduced by three-dimensional cosmic-ray modeling
| Autor: | Carmelo Evoli, Daniele Gaggero, Luca Maccione, Dario Grasso, Giuseppe Di Bernardo |
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| Rok vydání: | 2014 |
| Předmět: | |
| Zdroj: | Physical Review D. 89 |
| ISSN: | 1550-2368 1550-7998 |
| DOI: | 10.1103/physrevd.89.083007 |
| Popis: | The PAMELA collaboration recently released the ${e}^{+}$ absolute spectrum between 1 and 300 GeV in addition to the positron fraction and the ${e}^{\ensuremath{-}}$ spectrum previously measured in the same period. We use the newly developed three-dimensional upgrade of the dragon package to model those data. This code allows us to consider a realistic spiral-arm source distribution in the Galaxy, which impacts the high-energy shape of the propagated spectra. At low energy we treat solar modulation with the HelioProp code and compare its results with those obtained using the usual force-field approximation. We show that all PAMELA data sets can be consistently, and accurately, described in terms of a standard background on top of which a charge symmetric ${e}^{+}+{e}^{\ensuremath{-}}$ extra component with harder injection spectrum is added; this extra contribution is peaked at $\ensuremath{\sim}1--10\text{ }\text{ }\mathrm{TeV}$ and may originate from a diffuse population of sources located in the Galactic arms. For the first time, we compute the energy required to sustain such a relevant positron flux in the Galaxy, finding that it is naturally compatible with an astrophysical origin. We considered several reference propagation setups; we find that models with a low (or null) reacceleration---tuned against light nuclei data---nicely describe both PAMELA leptonic and hadronic data with no need to introduce a low-energy break in the proton and Helium spectra, as it would be required for high reacceleration models. We also compare our models with the preliminary ${e}^{\ensuremath{-}}$ and ${e}^{+}$ absolute spectra recently measured by AMS-02. We find that those data, differently from what is inferred from the positron fraction alone, favor a high energy cutoff $\ensuremath{\sim}10\text{ }\text{ }\mathrm{TeV}$ of the extra component if this is uniquely generated in the Galactic arms. A lower cutoff may be allowed if a relevant contribution from powerful ${e}^{\ensuremath{-}}+{e}^{+}$ nearby accelerators (e.g., one or few pulsars) is invoked. |
| Databáze: | OpenAIRE |
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