β\beta--Radioactive Cosmic Rays in a diffusion model: test for a local bubble?

In the present paper, we extend the analysis of Maurin et al. (2001) and Donato et al. (2001) to the $\beta$-radioactive nuclei $^{10}$Be, $^{26}$Al and $^{36}$Cl. These species are be shown to be particularly sensitive to the properties of the local interstellar medium (LISM). As studies of the LISM suggest that we live in an underdense bubble of extent r_{hole} \sim 50 - 200 \unit{pc}, this local feature must be taken into account. We present a modified version of our diffusion model which describes the underdensity as a hole in the galactic disc. It is found that the presence of the bubble leads to a decrease in the radioactive fluxes which can be approximated by a simple factor $\exp(-r_{hole}/l_{rad})$ where $l_{rad}=\sqrt{K \gamma \tau_0}$ is the typical distance travelled by a radioactive nucleus before it decays. We find that each of the radioactive nuclei independently point towards a bubble radius \lesssim 100 \unit{pc}. If these nuclei are considered simultaneously, only models with a bubble radius r_{hole} \sim 60 - 100 \unit{pc} are marginally consistent with data. In particular, the standard case r_{hole}=0 \unit{pc} is disfavoured. Our main concern is about the consistency of the currently available data, especially $^{26}$Al/$^{27}$Al.Comment: 21 pages, 11 figures, Latex, macro aa.cls, to appear in A&

Antiproton and Positron Signal Enhancement in Dark Matter Mini-Spikes Scenarios

The annihilation of dark matter (DM) in the Galaxy could produce specific imprints on the spectra of antimatter species in Galactic cosmic rays, which could be detected by upcoming experiments such as PAMELA and AMS02. Recent studies show that the presence of substructures can enhance the annihilation signal by a "boost factor" that not only depends on energy, but that is intrinsically a statistical property of the distribution of DM substructures inside the Milky Way. We investigate a scenario in which substructures consist of $\sim 100$ "mini-spikes" around intermediate-mass black holes. Focusing on primary positrons and antiprotons, we find large boost factors, up to a few thousand, that exhibit a large variance at high energy in the case of positrons and at low energy in the case of antiprotons. As a consequence, an estimate of the DM particle mass based on the observed cut-off in the positron spectrum could lead to a substantial underestimate of its actual value.Comment: 13 pages, 9 figures, minor changes, version accepted for publication in PR

CRDB: a database of charged cosmic rays

This paper gives a description of a new on-line database http://lpsc.in2p3.fr/crdb and associated on-line tools (data selection, data export, plots, etc.) for charged cosmic-ray measurements. The experimental setups (type, flight dates, techniques) from which the data originate are included in the database, along with the references to all relevant publications. The database relies on the MySQL5 engine. The web pages and queries are based on PHP, AJAX and the jquery, jquery.cluetip, jquery-ui, and table-sorter third-party libraries. In this first release, we restrict ourselves to Galactic cosmic rays with Z<=30 and a kinetic energy per nucleon up to a few tens of TeV/n. This corresponds to more than 200 different sub-experiments (i.e., different experiments, or data from the same experiment flying at different times) in as many publications. We set up a cosmic-ray database and provide tools to sort and visualise the data. New data can be submitted, providing the community with a collaborative tool to archive past and future cosmic-ray measurements. Any help/ideas to further expand and/or complement the database is welcome (please contact [email protected]).Comment: 13 pages, 6 figures: new Sect. 2.3 on Solar modulation parameters in CRDB v2.1, see http://lpsc.in2p3.fr/crd

TeV cosmic-ray proton and helium spectra in the myriad model

Recent measurements of cosmic ray proton and helium spectra show a hardening above a few hundreds of GeV. This excess is hard to understand in the framework of the conventional models of Galactic cosmic ray production and propagation. We propose here to explain this anomaly by the presence of local sources (myriad model). Cosmic ray propagation is described as a diffusion process taking place inside a two-zone magnetic halo. We calculate the proton and helium fluxes at the Earth between 50 GeV and 100 TeV. Improving over a similar analysis, we consistently derive these fluxes by taking into account both local and remote sources for which a unique injection rate is assumed. We find cosmic ray propagation parameters compatible with B/C measurements and for which the proton and helium spectra remarkably agree with the PAMELA and CREAM measurements over four decades in energy.Comment: 5 pages, 3 figure

Spallation dominated propagation of Heavy Cosmic Rays and the Local Interstellar Medium (LISM)

Measurements of ultra heavy nuclei at GeV/n energies in the galactic cosmic radiation address the question of the sources (nucleosynthetic s- and r-processes). As such, the determination of CR source abundances is a promising way to discriminate between existing nucleosynthesis models. For primary species (nuclei present and accelerated at sources), it is generally assumed that the relative propagated abundances, if they are close in mass, are not too different from their relative source abundances. Besides, the range of the correction factor associated to propagation has been estimated in weighted slab models only. Heavy CRs that are detected near Earth were accelerated from regions that are closer to us than were the light nuclei. Hence, the geometry of sources in the Solar neighbourhood, and as equally important, the geometry of gas in the same region, must be taken into account. In this paper, a two zone diffusion model is used, and as was previously investigated for radioactive species, we report here on the impact of the local interstellar medium (LISM) feature (under-dense medium over a scale ~100 pc) on primary and secondary stable nuclei propagated abundances. Going down to Fe nuclei, the connection between heavy and light abundances is also inspected. A general trend is found that decreases the UHCR source abundances relative to the HCR ones. This could have an impact on the level of r-process required to reproduce the data.Comment: 12 pages, 9 figures, accepted by A&A. Comparison with truncated weighted slab and discussion added. Figure 8 modified. New appendix on truncated weighted slab techniqu