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&

Direct constraints on diffusion models from cosmic-ray positron data: Excluding the Minimal model for dark matter searches

Galactic Cosmic-ray (CR) transport parameters are usually constrained by the boron-to-carbon ratio. This procedure is generically plagued with degeneracies between the diffusion coefficient and the vertical extent of the Galactic magnetic halo. The latter is of paramount importance for indirect dark matter (DM) searches, because it fixes the amount of DM annihilation or decay that contributes to the local antimatter CR flux. These degeneracies could be broken by using secondary radioactive species, but the current data still have large error bars, and this method is extremely sensitive to the very local interstellar medium (ISM) properties. Here, we propose to use the low-energy CR positrons in the GeV range as another direct constraint on diffusion models. We show that the PAMELA data disfavor small diffusion halo ($L\lesssim 3$ kpc) and large diffusion slope models, and exclude the minimal ({\em min}) configuration (Maurin et al. 2001, Donato et al. 2004) widely used in the literature to bracket the uncertainties in the DM signal predictions. This is complementary to indirect constraints (diffuse radio and gamma-ray emissions) and has strong impact on DM searches. Indeed this makes the antiproton constraints more robust while enhancing the discovery/exclusion potential of current and future experiments, like AMS-02 and GAPS, especially in the antiproton and antideuteron channels.Comment: 7 pages, 3 figures. V2: minor changes to match to the published version; misprints in Eqs.(4) fixe

Dark matter substructure modelling and sensitivity of the Cherenkov Telescope Array to Galactic dark halos

Hierarchical structure formation leads to a clumpy distribution of dark matter in the Milky Way. These clumps are possible targets to search for dark matter annihilation with present and future $\gamma$-ray instruments. Many uncertainties exist on the clump distribution, leading to disputed conclusions about the expected number of detectable clumps and the ensuing limits that can be obtained from non-detection. In this paper, we use the CLUMPY code to simulate thousands of skymaps for several clump distributions. This allows us to statistically assess the typical properties (mass, distance, angular size, luminosity) of the detectable clumps. Varying parameters of the clump distributions allows us to identify the key quantities to which the number of detectable clumps is the most sensitive. Focusing our analysis on two extreme clump configurations, yet consistent with results from numerical simulations, we revisit and compare various calculations made for the Fermi-LAT instrument, in terms of number of dark clumps expected and the angular power spectrum for the Galactic signal. We then focus on the prospects of detecting dark clumps with the future CTA instrument, for which we make a detailed sensitivity analysis using open-source CTA software. Based on a realistic scenario for the foreseen CTA extragalactic survey, and accounting for a post-trial sensitivity in the survey, we show that we obtain competitive and complementary limits to those based on long observation of a single bright dwarf spheroidal galaxy.Comment: 29 pages + appendix, 15 figures. V2: Sects. 3.3, 4, and 5.3 extended, results unchanged (matching accepted JCAP version

Rayonnement cosmique et détection indirecte de matière noire

This document consists of two parts and two annexes. In chapter 1, I present the nuclear component of the galactic cosmic radiation, and discuss astrophysical and dark matter issues. Chapter 2 is devoted to the study of gamma-ray emissions from the annihilation of dark matter. The common thread is the indirect search for dark matter, which relies on the signal and astrophysical background modelling. Each part provides an introduction to the subject, an overview, a compilation of results and some perspectives and research directions to develop for the coming years. To conclude, I underline the link and complementarity between charged and neutral particle studies for galactic and extragalactic objects. Appendix A presents some public tools developed for these studies. Appendix B is more personal, and provides my CV and describes my role supervising master and PhD students.Ce document est constitué de deux parties et de deux annexes . Dans le chap. 1, je parle de la composante nucléaire du rayonnement cosmique galactique, des enjeux astrophysiques et ceux reliés à la matière noire. Le chap. 2 est consacré à l'étude des émissions gamma dues à l'annihilation de matière noire. Le fil conducteur est la recherche indirecte de matière noire, qui passe par la maîtrise du signal et des fonds astrophysiques. Chaque partie propose une introduction du sujet, un état des lieux, une compilation des résultats obtenus et quelques perspectives et directions de recherches à développer pour les années à venir. La conclusion générale revient sur le lien et la complémentarité des particules chargés et neutres et l'articulation de ces deux messagers pour de futures études hors de la Galaxie. L'annexe A présente quelques outils développés utilisés pour ces études et qui ont été rendus publics. L'annexe B, un peu plus personnelle, revient sur mon parcours, mon CV et le rôle que j'ai pu avoir dans l'encadrement d'étudiants de master et de thèse et dans l'animation scientifique

Design and analysis of a foldable / unfoldable corrugated architectural curved envelop

11 pagesInternational audienceOrigami and paperfolding techniques may inspire the design of structures that have the ability to be folded and unfolded: their geometry can be changed from an extended, servicing state to a compact one, and back-forth. In traditional Origami, folds are introduced in a sheet of paper (a developable surface) for transforming its shape, with artistic or decorative intent; in recent times the ideas behind origami techniques were transferred in various design disciplines to build developable foldable / unfoldable structures, mostly in aerospace industry. The geometrical arrangement of folds allows a folding mechanism of great efficiency and is often derived from the buckling patterns of simple geometries, like a plane or a cylinder (e.g. Miura-Ori and Yoshimura folding pattern). Here we interest ourselves to the conception of foldable / unfoldable structures for civil engineering and architecture. In those disciplines, the need for folding efficiency comes along with the need for structural efficiency (stiffness); for this purpose we will explore nondevelopable foldable / unfoldable structures: those structures exhibit potential stiffness because, when unfolded, they cannot be flattened to a plane (non-developability). In this paper we propose a classification for foldable / unfoldable surfaces that comprehend non fully developable (and also non fully foldable) surfaces and a method for the description of folding motion. Then we propose innovative geometrical configurations for those structures by generalizing the Miura-Ori folding pattern to non-developable surfaces that, once unfolded, exhibit curvature

Kaluza-Klein Dark Matter and Galactic Antiprotons

Extra dimensions offer new ways to address long-standing problems in beyond the standard model particle physics. In some classes of extra-dimensional models, the lightest Kaluza-Klein particle is a viable dark matter candidate. In this work, we study indirect detection of Kaluza-Klein dark matter via its annihilation into antiprotons. We use a sophisticated galactic cosmic ray diffusion model whose parameters are fully constrained by an extensive set of experimental data. We discuss how fluxes of cosmic antiprotons can be used to exclude low Kaluza-Klein masses.Comment: 14 pages, 7 figures, 3 table

Current status and desired accuracy of the isotopic production cross-sections relevant to astrophysics of cosmic rays II. Fluorine to Silicon (and updated LiBeB)

High-precision cosmic-ray data from ongoing and recent past experiments (Voyager, ACE-CRIS, PAMELA, ATIC, CREAM, NUCLEON, AMS-02, CALET, DAMPE) are being released in the tens of MeV/n to multi-TeV/n energy range. Astrophysical and dark matter interpretations of these data are limited by the precision of nuclear production cross-sections. In Paper I, PRC 98, 034611 (2018), we set up a procedure to rank nuclear reactions whose desired measurements will enable us to fully exploit currently available data on CR Li to N ($Z=3-7$) species. Here we extend these rankings to O up to Si nuclei ($Z=8-14$), also updating our results on the LiBeB species. We also highlight how comprehensive new high precision nuclear data, that could e.g. be obtained at the SPS at CERN, would be a game-changer for the determination of key astrophysical quantities (diffusion coefficient, halo size of the Galaxy) and indirect searches for dark matter signatures.Comment: 38 pages (18p main text + 20p App.), 17 figures, 16 tables (all f_abc coeffs available at https://doi.org/10.5281/zenodo.8143305

Cosmic-ray ransport parameters and fluorine source abundance from AMS-02 F/Si data

The AMS-02 collaboration recently released cosmic-ray data of unprecedented accuracy for F/Si. In this work, we have studied if this new data can be reproduced by propagation models tuned on lighter secondary-to-primary ratios (Li/C, Be/C, B/C), and how much F at source can be accommodated by the new data, using a 1D diffusion model (USINE code) and performing χ2 analyses accounting for several systematics (energy correlations in data, nuclear cross-sections, and solar modulation uncertainties). The model tuned on Li/C, Be/C, and B/C AMS-02 data overshoots F/Si data by 10-15%. However, this difference can be explained by the 19F production cross-sections uncertainties from a few dominant channels (60% of the produced F comes from the fragmentation of 20Ne, 24Mg, and 28Si). We concluded that all secondary species from Li to F can be explained by the same transport parameters. Additionally, we also draw limits on the F source abundance (relative to Si)