Implications of Lithium to Oxygen AMS-02 spectra on our understanding of cosmic-ray diffusion. (arXiv:2103.09824v2 [astro-ph.HE] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Korsmeier_M/0/1/0/all/0/1">Michael Korsmeier</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cuoco_A/0/1/0/all/0/1">Alessandro Cuoco</a>
We analyze recent AMS-02 comic-ray measurements of Lithium, Beryllium, Boron,
Carbon, Nitrogen and Oxygen. The emphasis of the analysis is on systematic
uncertainties related to propagation and nuclear cross sections. To investigate
the uncertainties in the propagation scenario, we consider five different
frameworks, differing with respect to the inclusion of a diffusion break at a
few GV, the presence of reacceleration, and the presence of a break in the
injection spectra of primaries. For each framework we fit the diffusion
equations of cosmic rays and explore the parameter space with Monte Carlo
methods. At the same time, the impact of the uncertainties in the nuclear
production cross sections of secondaries is explicitly considered and included
in the fit through the use of nuisance parameters. We find that all the
considered frameworks are able to provide a good fit. In particular, two
competing scenarios, one including a break in diffusion but no reacceleration
and the other with reacceleration but no break in diffusion are both allowed.
The inclusion of cross-section uncertainties is, however, crucial, to this
result. Thus, at the moment, these uncertainties represent a fundamental
systematic preventing a deeper understanding of the properties of CR
propagation. We find, nonetheless, that the slope of diffusion at intermediate
rigidities is robustly constrained in the range $deltasimeq0.45-0.5$ in
models without convection, or $deltasimeq0.4-0.5$ if convection is included
in the fit. Furthermore, we find that the use of the AMS-02 Beryllium data
provides a lower limit on the vertical size of the Galactic propagation halo of
$z_mathrm{h}gtrsim3$ kpc.
We analyze recent AMS-02 comic-ray measurements of Lithium, Beryllium, Boron,
Carbon, Nitrogen and Oxygen. The emphasis of the analysis is on systematic
uncertainties related to propagation and nuclear cross sections. To investigate
the uncertainties in the propagation scenario, we consider five different
frameworks, differing with respect to the inclusion of a diffusion break at a
few GV, the presence of reacceleration, and the presence of a break in the
injection spectra of primaries. For each framework we fit the diffusion
equations of cosmic rays and explore the parameter space with Monte Carlo
methods. At the same time, the impact of the uncertainties in the nuclear
production cross sections of secondaries is explicitly considered and included
in the fit through the use of nuisance parameters. We find that all the
considered frameworks are able to provide a good fit. In particular, two
competing scenarios, one including a break in diffusion but no reacceleration
and the other with reacceleration but no break in diffusion are both allowed.
The inclusion of cross-section uncertainties is, however, crucial, to this
result. Thus, at the moment, these uncertainties represent a fundamental
systematic preventing a deeper understanding of the properties of CR
propagation. We find, nonetheless, that the slope of diffusion at intermediate
rigidities is robustly constrained in the range $deltasimeq0.45-0.5$ in
models without convection, or $deltasimeq0.4-0.5$ if convection is included
in the fit. Furthermore, we find that the use of the AMS-02 Beryllium data
provides a lower limit on the vertical size of the Galactic propagation halo of
$z_mathrm{h}gtrsim3$ kpc.
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