Secondary Antiprotons and Propagation of Cosmic Rays in the Galaxy and Heliosphere
Abstract
High-energy collisions of cosmic-ray nuclei with interstellar gas are believed to be the mechanism producing the majority of cosmic-ray antiprotons. Because of the kinematics of the process, they are created with a nonzero momentum; the characteristic spectral shape with a maximum at ~2 GeV and a sharp decrease toward lower energies makes antiprotons a unique probe of models for particle propagation in the Galaxy and modulation in the heliosphere. On the other hand, accurate calculation of the secondary antiproton flux provides a ``background'' for searches for exotic signals from the annihilation of supersymmetric particles and primordial black hole evaporation. Recently, new data with large statistics on both low- and high-energy antiproton fluxes have become available which allow such tests to be performed. We use our propagation code GALPROP to calculate interstellar cosmic-ray propagation for a variety of models. We show that there is no simple model capable of accurately describing the whole variety of data: boron/carbon and sub-iron/iron ratios, spectra of protons, helium, antiprotons, positrons, electrons, and diffuse γ-rays. We find that only a model with a break in the diffusion coefficient plus convection can reproduce measurements of cosmic-ray species, and the reproduction of primaries (p, He) can be further improved by introducing a break in the primary injection spectra. For our best-fit model we make predictions of proton and antiproton fluxes near the Earth for different modulation levels and magnetic polarity using a steady state drift model of propagation in the heliosphere.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 2002
- DOI:
- 10.1086/324402
- arXiv:
- arXiv:astro-ph/0106567
- Bibcode:
- 2002ApJ...565..280M
- Keywords:
-
- ISM: Cosmic Rays;
- Elementary Particles;
- Galaxy: General;
- ISM: General;
- Nuclear Reactions;
- Nucleosynthesis;
- Abundances;
- Astrophysics;
- High Energy Physics - Phenomenology;
- Nuclear Experiment;
- Nuclear Theory
- E-Print:
- Many Updates, 20 pages, 15 ps-figures, emulateapj5.sty. To be published in ApJ v.564 January 10, 2002 issue. More details can be found at http://www.gamma.mpe-garching.mpg.de/~aws/aws.html