Propagation of ultra-high-energy cosmic rays and their secondaries with CRPropa

van Vliet, Arjen René

Report/Dissertation / PhD Thesis

PUBDB-2015-01957

Propagation of ultra-high-energy cosmic rays and their secondaries with CRPropa

van Vliet, A. R. (Corresponding Author)

2015
Verlag Deutsches Elektronen-Synchrotron

Verlag Deutsches Elektronen-Synchrotron, DESY-THESIS 153 pp. (2015) [10.3204/DESY-THESIS-2015-014] = Universität Hamburg, Diss., 2014

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Please use a persistent id in citations: doi:10.3204/DESY-THESIS-2015-014

Report No.: DESY-THESIS-2015-014

Abstract: Due to experiments like the Pierre Auger Observatory (Auger) and the Telescope Array (TA), high-statistics data is becoming available on the energy spectrum, the composition and the arrival directions of ultra-high-energy cosmic rays (UHECRs, cosmic rays with energies above $\sim 10^{17}$ eV). To interpret this data in terms of actual astrophysical parameters, or to test astrophysical models against the measured data, dedicated simulations of the propagation of UHECRs from their sources to Earth are needed. To this end, the UHECR propagation code called CRPropa has been developed. It can take into account all relevant interactions with ambient photon backgrounds (pair production, photodisintegration and photopion production) as well as nuclear decay, cosmological evolution effects and deflections in extragalactic and galactic magnetic fields. CRPropa, including its newest features, is described in this thesis. When considering the propagation of ultra-high-energy nuclei, the dominant interaction for most isotopes and energies is photodisintegration. Photodisintegration has been implemented in CRPropa for all relevant isotopes (up to iron) and all relevant photodisintegration channels using cross-section calculations with the publicly-available code called TALYS, including extensions for the low mass numbers. This photodisintegration setup is compared here extensively with the photodisintegration scheme developed by Puget, Stecker and Bredekamp, leading to several improvements on the cross sections implemented in CRPropa. In the interactions of UHECRs with background photon fields, secondary neutrinos and photons, so-called cosmogenic neutrinos and photons, can be created. CRPropa can simulate the production and propagation of these secondary particles as well. The IceCube Neutrino Observatory (IceCube) has recently reported the first observation of extraterrestrial neutrinos in the PeV energy range. In this work is investigated whether these neutrinos could have originated as secondaries from UHECR interactions, taking into account limits on the cosmogenic photon flux. We show that the IceCube events are most likely not cosmogenic neutrinos. An additional way to constrain astrophysical models is by looking at the arrival directions of UHECRs. Many different investigations into anisotropies in the UHECR sky have been reported. For instance, Auger has done a search for an equatorial dipole in the UHECR arrival directions. The measured amplitudes of this dipole are compared in this thesis with simulations of realistic scenarios of the UHECR universe. In this way these scenarios can be tested against the measured data. Furthermore, the effects of specific components of the UHECR universe on the dipole amplitude, as e.g. the deflections of UHECRs in galactic and extragalactic magnetic fields and the source density of UHECR sources, are investigated. Here it is shown that, for the investigated scenarios, the deflections in both aforementioned magnetic fields have a significant effect on the expected dipole amplitude, while no strong dependence on the source density has been found.

Keyword(s): Dissertation

Note: Universität Hamburg, Diss., 2014

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