arXiv subjects

Fiorenza Donato

Publications and source records attributed to Fiorenza Donato.

60 records · Page 4Linked to original sources

arXiv2003

Stable and Radioactive Nuclei in a Diffusion Model

We present the results on the source spectrum function for primary nuclei in galactic cosmic rays, where two distinct energy dependences are used for the source spectra. We discuss the evolution of the goodness of fit to B/C data with the propagation parameters and also show that the results are not much affected by a different choice for the diffusion scheme. We apply the constraints on the diffusion scheme as derived from stable nuclei to calculate the propagation of beta-radioactive isotopes. The diffusion model is refined to properly take into account the effect of a local bubble in the interstellar medium. Our calculations are compared to existing data, which prefer the local bubble description instead of the homogeneus scheme.

astro-ph↗

arXiv2002

Galactic Cosmic Ray Nuclei as a Tool for Astroparticle Physics

Cosmic Ray nuclei in the energy range 100 MeV/nuc - 100 GeV/nuc provide crucial information about the physical properties of the Galaxy. They can also be used to answer questions related to astroparticle physics. This paper reviews the results obtained in this direction, with a strong bias towards the work done by the authors at {\sc lapth}, {\sc isn} and {\sc iap}. The propagation of these nuclei is studied quantitatively in the framework of a semi-analytical two-zone diffusion model taking into account the effect of galactic wind, diffuse reacceleration and energy losses. The parameters of this model are severely constrained by an analysis of the observed B/C ratio. These constraints are then used to study other species such as radioactive species and light antinuclei. Finally, we focus on the astroparticle subject and we study the flux of antiprotons and antideuterons that might be due to neutralino annihilations or primordial black hole evaporation. The question of the spatial origin of all these species is also addressed.

astro-ph↗

arXiv2002

New results on source and diffusion spectral features of Galactic cosmic rays: I- B/C ratio

In a previous study (Maurin et al., 2001), we explored the set of parameters describing diffusive propagation of cosmic rays (galactic convection, reacceleration, halo thickness, spectral index and normalization of the diffusion coefficient), and we identified those giving a good fit to the measured B/C ratio. This study is now extended to take into account a sixth free parameter, namely the spectral index of sources. We use an updated version of our code where the reacceleration term comes from standard minimal reacceleration models. The goal of this paper is to present a general view of the evolution of the goodness of fit to B/C data with the propagation parameters. In particular, we find that, unlike the well accepted picture, and in accordance with our previous study, a Kolmogorov-like power spectrum for diffusion is strongly disfavored. Rather, the $χ^2$ analysis points towards $δ\gtrsim 0.7$ along with source spectra index $\lesssim 2.0$. Two distinct energy dependences are used for the source spectra: the usual power-law in rigidity and a law modified at low energy, the second choice being only slightly preferred. We also show that the results are not much affected by a different choice for the diffusion scheme. Finally, we compare our findings to recent works, using other propagation models. This study will be further refined in a companion paper, focusing on the fluxes of cosmic ray nuclei.

astro-ph↗

arXiv2001

$β$--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 $β$-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 $l_{rad}=\sqrt{K γτ_0}$ 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.

astro-ph↗

arXiv2000

Antimatter from supersymmetric dark matter

We propose low-energy antideuterons in cosmic rays as a new possible signature for indirect detection of supersymmetric dark matter. Since the energy spectrum of the antiproton secondary component is still spoilt by considerable theoretical uncertainties, looking for low-energy antideuterons seems a plausible alternative. We apply our calculation to the AMS experiment, when mounted on the International Spatial Station. If a few low-energy antideuterons will be discovered by AMS, this should be seriously taken as a clue for the existence of relic, massive neutralinos in the dark halo of our Galaxy.

hep-ph↗

arXiv1998

Cosmic-ray antiprotons from neutralino annihilation in the halo

We report the main results of a paper where recent data of low-energy cosmic-ray $\bar p$ spectrum have been analyzed in terms of newly calculated fluxes for secondary antiprotons and for a possible contribution of an exotic signal due to neutralino annihilation in the galactic halo. We also present the results of a paper in which we have proved that a sizeable fraction of the supersymmetric neutralino configurations, singled out by the DAMA/NaI data on a possible annual modulation effect in WIMP direct search, may provide detectable cosmic-ray antiproton signals.

hep-ph↗