Abstract
PAMELA and, more recently, AMS-02, are ushering us into a new era of greatly reduced statistical uncertainties in experimental measurements of cosmic ray fluxes. In particular, new determinations of traditional diagnostic tools such as the boron to carbon ratio (B/C) are expected to significantly reduce errors on cosmic-ray diffusion parameters, with important implications for astroparticle physics, ranging from inferring primary source spectra to indirect dark matter searches. It is timely to stress, however, that the conclusions inferred crucially depend on the framework in which the data are interpreted as well as on some nuclear input parameters. We aim at assessing the theoretical uncertainties affecting the outcome, with models as simple as possible while still retaining the key dependences. We compare different semi-analytical, two-zone model descriptions of cosmic ray transport in the Galaxy: infinite slab(lD), cylindrical symmetry (2D) with homogeneous sources, cylindrical symmetry (2D) with inhomogeneous source distribution. We tested for the effect of a primary source contamination in the boron flux by parametrically altering its flux. We also tested for nuclear cross-section uncertainties.
Highlights
The pattern of relative abundances of nuclei in the cosmic radiation (CR) is roughly similar to the one of the solar system material, with some notable exceptions: fragile nuclei such as 2H or Li-Be-B are over-represented in CR
We find that the main theoretical bias on the determination of the diffusion coefficient index δ is represented by the assumption that no injection of boron takes place at the source
An inhomogeneous source distribution marginally alters the central value of the diffusion coefficient normalisation
Summary
The pattern of relative abundances of nuclei in the cosmic radiation (CR) is roughly similar to the one of the solar system material, with some notable exceptions: fragile nuclei (with low binding energies) such as 2H or Li-Be-B are over-represented in CR. 2 we recall a simple 1D diffusion model providing our benchmark for the following analyses This model certainly has pedagogical value, since it allows encoding the main dependences of the B/C ratio on input as well as astrophysical parameters in simple analytical formulae. Y. Genolini et al.: Theoretical uncertainties in extracting cosmic-ray diffusion parameters: the boron-to-carbon ratio index α for all nuclei. Althought most of the isotopes at stake are stable, radioactive nuclei were taken into account in the calculation, and we obtained more complicated expressions for the fluxes, which are not displayed here for brevity They are reported for instance in Appendix A of Putze et al (2010).
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