Vivian Poulin

Learn More
aInstitut de Théorie des Phénomènes Physiques, École Polytechnique Fédérale de Lausanne, CH-1015, Lausanne, Switzerland bInstitut de Ciències del Cosmos, Universitat de Barcelona, IEEC-UB, Mart́ı i Franquès 1, E08028 Barcelona, Spain cDept. d’Astronomia i Meteorologia, Institut de Ciències del Cosmos, Universitat de Barcelona, IEEC-UB, Mart́ı i Franquès 1,(More)
Context. The positron fraction in cosmic rays has recently been measured with improved accuracy up to 500 GeV, and it was found to be a steadily increasing function of energy above ∼ 10 GeV. This behaviour contrasts with standard astrophysical mechanisms, in which positrons are secondary particles, produced in the interactions of primary cosmic rays during(More)
The standard theory of electromagnetic cascades onto a photon background predicts a quasiuniversal shape for the resulting nonthermal photon spectrum. This has been applied to very disparate fields, including nonthermal big bang nucleosynthesis (BBN). However, once the energy of the injected photons falls below the pair-production threshold the spectral(More)
Using the updated proton and helium fluxes just released by the Ams-02 experiment we reevaluate the secondary astrophysical antiproton to proton ratio and its uncertainties, and compare it with the ratio preliminarly reported by Ams-02. We find no unambiguous evidence for a significant excess with respect to expectations. Yet, some preference for a flatter(More)
Using cosmic-ray boron to carbon ratio (B/C) data recently released by the Ams-02 experiment, we find indications (decisive evidence, in Bayesian terms) in favor of a diffusive propagation origin for the broken power-law spectra found in protons (p) and helium nuclei (He). The result is robust with respect to currently estimated uncertainties in the cross(More)
  • 1