Numerical Study of Cosmic-Ray Elemental and Leptonic Spectra

Cosmic rays undergo various propagation processes, including diffusion, reacceleration, and convection, as they travel through the galaxy following acceleration. These propagation processes affect all species of cosmic rays simultaneously, allowing complementary constraints to be placed on models of propagation by multiple datasets at once. Leptonic data, in particular measurements of the cosmic-ray electron and positron spectra, are particularly sensitive probes of propagation models. We examine the energy dependence of cosmic-ray elemental and leptonic spectra simultaneously in the diffusive halo model of cosmic-ray propagation. We use GALPROP, a numerical cosmic-ray propagation code, and MINUIT2, an optimization library, to compute predicted cosmic-ray spectra and assess their goodness-of-fit to experimental data. Three cases are considered to reproduce the behavior of the data below ~100 GeV/n: a break in the diffusion coefficient, a break in the source injection spectrum, and a combination of both. The goodness-of-fit to the data under these scenarios is assessed. Uncertainties in the fit parameters from both the fitting routine and from model uncertainties are included in this assessment.