A common solution to the cosmic ray anisotropy and gradient problems

Multichannel Cosmic Ray (CR) spectra and the large scale CR anisotropy can hardly be made compatible in the framework of conventional isotropic and homogeneous propagation models. These models also have problems explaining the longitude distribution and the radial emissivity gradient of the $\gamma$-ray galactic interstellar emission. We argue here that accounting for a well physically motivated correlation between the CR escape time and the spatially dependent magnetic turbulence power can naturally solve both problems. Indeed, by exploiting this correlation we find propagation models that fit a wide set of CR primary and secondary spectra, and consistently reproduce the CR anisotropy in the energy range 10^2 - 10^4 \GeV and the $\gamma$-ray longitude distribution recently measured by Fermi-LAT.Comment: 4 pages, 3 figures. v2: Accepted in Phys. Rev. Let

Secondary antiprotons as a Galactic Dark Matter probe

We present a novel determination of the astrophysical uncertaintiesassociated to the secondary antiproton flux originating from cosmic-rayspallation on the interstellar gas. We select a set of propagation modelscompatible with the recent B/C data from PAMELA, and find those providingminimal and maximal antiproton fluxes in different energy ranges. We use thisresult to determine the most conservative bounds on relevant Dark Matter (DM)annihilation channels: We find that the recent claim of a DM interpretation ofa gamma-ray excess in the Galactic Center region cannot be ruled out by currentantiproton data. Finally, we discuss the impact of the recently releasedpreliminary data from AMS-02. In particular, we provide a reference modelcompatible with proton, helium and B/C spectra from this experiment.Remarkably, the main propagation parameters of this model are in agreement withthe best fit presented in our earlier statistical analyses. We also show thatthe antiproton-to-proton ratio does not exhibit any significant anomaly at highenergy with respect to our predictions

A consistent interpretation of recent CR nuclei and electron spectra

We try to interpret the recently updated measurement of the cosmic ray electron (CRE) spectrum observed by Fermi-LAT, together with PAMELA data on positron fraction, in a single-component scenario adopting different propagation setups; we find that the model is not adequate to reproduce the two datasets, so the evidence of an extra primary component of electrons and positrons is strengthened. Instead, a double component scenario computed in a Kraichnan-like diffusion setup (which is suggested by B/C and $\bar{p}$ data) gives a satisfactory fit of all exisiting measurements. We confirm that nearby pulsars are good source candidates for the required $e^\pm$ extra-component and we show that the predicted CRE anisotropy in our scenario is compatible with Fermi-LAT recently published constraints.Comment: Accepted for the publication in the proceedings of the ICATPP Conference on Cosmic Rays for Particle and Astroparticle Physics, Villa Olmo (Como), Oct. 201

Cosmic-ray propagation with DRAGON2: II. Nuclear interactions with the interstellar gas

Understanding the isotopic composition of cosmic rays (CRs) observed near Earth represents a milestone towards the identification of their origin. Local fluxes contain all the known stable and long-lived isotopes, reflecting the complex history of primaries and secondaries as they traverse the interstellar medium. For that reason, a numerical code which aims at describing the CR transport in the Galaxy must unavoidably rely on accurate modelling of the production of secondary particles. In this work we provide a detailed description of the nuclear cross sections and decay network as implemented in the forthcoming release of the galactic propagation code DRAGON2. We present the secondary production models implemented in the code and we apply the different prescriptions to compute quantities of interest to interpret local CR fluxes (e.g., nuclear fragmentation timescales, secondary and tertiary source terms). In particular, we develop a nuclear secondary production model aimed at accurately computing the light secondary fluxes (namely: Li, Be, B) above 1 GeV/n. This result is achieved by fitting existing empirical or semi-empirical formalisms to a large sample of measurements in the energy range 100 MeV/n to 100 GeV/n and by considering the contribution of the most relevant decaying isotopes up to iron. Concerning secondary antiparticles (positrons and antiprotons), we describe a collection of models taken from the literature, and provide a detailed quantitative comparison.Comment: 22 pages, 12 figure