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A precision measurement by the Alpha Magnetic Spectrometer on the International Space Station of the positron fraction in primary cosmic rays in the energy range from 0.5 to 350 GeV based on 6.8×106 positron and electron events is presented. The very accurate data show that the positron fraction is steadily increasing from 10 to ∼250  GeV, but, from 20 to 250 GeV, the slope decreases by an order of magnitude. The positron fraction spectrum shows no fine structure, and the positron to electron ratio shows no observable anisotropy. Together, these features show the existence of new physical phenomena

Cosmic-ray nuclei Ñuxes are expected to be measured with high precision in the near future. For instance, high-quality data on the antiproton component could give important clues about the nature of the astronomical dark matter. A very good understanding of the di †erent aspects of cosmic-ray propagation is therefore necessary. In this paper, we use cosmic-ray nuclei data to give constraints on the di †u-sion parameters. Propagation is studied with semianalytical solutions of a di †usion model, and we give new analytical solutions for radioactively produced species. Our model includes convection and reacceleration, as well as the standard energy losses. We perform a s2 analysis over B/C data for a large number of conÐgurations obtained by varying the relevant parameters of the di †usion model. A very good agreement with B/C data arises for a number of conÐgurations, all of which are compatible with sub-Fe/Fe data. Di †erent source spectra Q(E) and di †usion coefficients K(E) have been tried, but for both parameters only one form gives a good Ðt. Another important result is that models without convection or without reacceleration are excluded. We Ðnd that the various parameters, i.e., the di †usion coefficient normalization and spectral index d, the halo thickness L , the velocity and the K 0 Alfven V A , convection velocity are strongly correlated. We obtain limits on the spectral index d of the di †usion V c coefficient, and in particular we exclude a Kolmogorov spectrum (d \ 13 ).

We calculate the antiproton flux due to relic neutralino annihilations, in a two-dimensional diffusion model compatible with stable and radioactive cosmic ray nuclei. We find that the uncertainty in the primary flux induced by the propagation parameters alone is about two orders of magnitude at low energies, and it is mainly determined by the lack of knowledge on the thickness of the diffusive halo. On the contrary, different dark matter density profiles do not significantly alter the flux: a NFW distribution produces fluxes which are at most 20% higher than an isothermal sphere. The most conservative choice for propagation parameters and dark matter distribution normalization, together with current data on cosmic antiprotons, cannot lead to any definitive constraint on the supersymmetric parameter space, neither in a low-energy effective MSSM, or in a minimal SUGRA scheme. However, if the best choice for propagation parameters -corresponding to a diffusive halo of L = 4 kpc -is adopted, some supersymmetric configurations with the neutralino mass mχ < ∼ 100 GeV should be considered as excluded. An enhancement flux factor -due for instance to a clumpy dark halo or to a higher local dark matter density -would imply a more severe cut on the supersymmetric parameters.PACS numbers: 95.35.+d,98.35.Gi,98.35.Pr,98.70.Sa,11.30.Pb,12.60.Jv,95.30.Cq

International audienceA precision measurement by AMS of the antiproton flux and the antiproton-to-proton flux ratio inprimary cosmic rays in the absolute rigidity range from 1 to 450 GV is presented based on 3.49 × 105antiproton events and 2.42 × 109 proton events. The fluxes and flux ratios of charged elementary particlesin cosmic rays are also presented. In the absolute rigidity range ∼60 to ∼500 GV, the antiproton ¯p, protonp, and positron eþ fluxes are found to have nearly identical rigidity dependence and the electron e− fluxexhibits a different rigidity dependence. Below 60 GV, the ( ¯ p=p), ( ¯ p=eþ), and (p=eþ) flux ratios eachreaches a maximum. From ∼60 to ∼500 GV, the ( ¯ p=p), ( ¯ p=eþ), and (p=eþ) flux ratios show no rigiditydependence. These are new observations of the properties of elementary particles in the cosmos

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The Cherenkov Telescope Array (CTA) is a new observatory for very high-energy (VHE) gamma rays. CTA has ambitions science goals, for which it is necessary to achieve full-sky coverage, to improve the sensitivity by about an order of magnitude, to span about four decades of energy, from a few tens of GeV to above 100 TeV with enhanced angular and energy resolutions over existing VHE gamma-ray observatories. An international collaboration has formed with more than 1000 members from 27 countries in Europe, Asia, Africa and North and South America. In 2010 the CTA Consortium completed a Design Study and started a three-year Preparatory Phase which leads to production readiness of CTA in 2014. In this paper we introduce the science goals and the concept of CTA, and provide an overview of the project. ?? 2013 Elsevier B.V. All rights reserved