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- Di Mauro, Mattia, et al.
(författare)
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Novel prediction for secondary positrons and electrons in the Galaxy
- 2023
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Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 108:6
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Tidskriftsartikel (refereegranskat)abstract
- The Galactic flux of cosmic-ray (CR) positrons in the GeV to TeV energy range is very likely due to different Galactic components. One of these is the inelastic scattering of CR nuclei with the atoms of the interstellar medium. The precise amount of this component determines the eventual contribution from other sources. We present here a new estimation of the secondary CR positron flux by incorporating the latest results for the production cross sections of e± from hadronic scatterings calibrated on collider data. All the reactions for CR nuclei up to silicon scattering on both hydrogen and helium are included. The propagation models are derived consistently by fits on primary and secondary CR nuclei data. Models with a small halo size (L≤2 kpc) are disfavored by the nuclei data although the current uncertainties on the beryllium nuclear cross sections may impact this result. The resulting positron flux shows a strong dependence on the Galactic halo size, increasing up to factor 1.5 moving L from 8 kpc to 2 kpc. Within the most reliable propagation models, the positron flux matches the data for energies below 1 GeV. We verify that secondary positrons contribute less than 70% of the data above a few GeV, corroborating that an excess of positrons is already present at very low energies. At larger energies, our predictions are below the data with the discrepancy becoming more and more pronounced. Our results are provided together with uncertainties due to propagation and hadronic cross sections. The former uncertainties are below 5% at fixed L, while the latter are about 7% almost independently of the propagation scheme. In addition to the predictions of positrons, we provide new predictions also for the secondary CR electron flux.
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| 2. |
- Orusa, Luca, et al.
(författare)
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New determination of the production cross section for γ rays in the Galaxy
- 2023
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Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 107:8
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Tidskriftsartikel (refereegranskat)abstract
- The flux of γ rays is measured with unprecedented accuracy by the Fermi Large Area Telescope from 100 MeV to almost 1 TeV. In the future, the Cherenkov Telescope Array will have the capability to measure photons up to 100 TeV. To accurately interpret this data, precise predictions of the production processes, specifically the cross section for the production of photons from the interaction of cosmic-ray protons and helium with atoms of the ISM, are necessary. In this study, we determine new analytical functions describing the Lorentz-invariant cross section for γ-ray production in hadronic collisions. We utilize the limited total cross section data for π0 production channels and supplement this information by drawing on our previous analyses of charged pion production to infer missing details. In this context, we highlight the need for new data on π0 production. Our predictions include the cross sections for all production channels that contribute down to the 0.5% level of the final cross section, namely η, K+, K−, K0S, and K0L mesons as well as Λ, Σ, and Ξ baryons. We determine the total differential cross section dσ(p+p→γ+X)/dEγ from 10 MeV to 100 TeV with an uncertainty of 10% below 10 GeV of γ-ray energies, increasing to 20% at the TeV energies. We provide numerical tables and a script for the community to access our energy-differential cross sections, which are provided for incident proton (nuclei) energies from 0.1 GeV to 107 GeV (GeV/n).
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