Abstract
Photohadronic interactions are important for the sources and the transport of Ultra-High Energy Cosmic Rays (UHECRs). Current state-of-the-art cosmic ray transport simulations handle nuclear disintegration at energies of the Giant Dipole Resonance at a more sophisticated level, as well as the photohadronic interactions of nucleons in the high-energy regime above the pion production threshold. However, the interactions of nuclei above the pion production threshold are commonly modeled by treating the nucleus as a superposition of free nucleons—ignoring the effect of the nuclear medium. We construct an improved, inclusive model for the photomeson regime for nuclei with A ⩽ 56 by employing more accurate, data-driven parametrizations of the interaction cross section, the fragmentation of the primary nucleus and the inclusive pion production cross section that directly affects the production of astrophysical neutrinos. We apply our results to two multi-messenger scenarios (Tidal Disruption Events and Gamma-Ray Bursts) in which photonuclear interactions in the photomeson regime are the dominant cooling process for the highest energy cosmic rays. While we find moderate changes to the mass composition of UHECRs, the astrophysical neutrino fluxes exhibit a significant (factor of a few) reduction compared to the naive superposition of free nucleons for sources of UHECR nuclei with a populated cascade. The numerical code implementing the model has been made publicly available, which facilitates the integration of our results in similar frameworks.
Highlights
While we find moderate changes to the mass composition of Ultra-High Energy Cosmic Rays (UHECRs), the astrophysical neutrino fluxes exhibit a significant reduction compared to the naive superposition of free nucleons for sources of UHECR nuclei with a populated cascade
Apart from the primary UHECRs, the neutrino production is always related to the photomeson regime: if the neutrinos are mostly produced off nuclei, corrections to the photomeson model are expected to have an impact, whereas if the neutrinos are produced off nucleons, the physics is well described by, for instance, Sophia
We have scrutinized a commonly adopted approach in the literature known as Single Particle Model (SPM), and introduced an improved description: the Empirical Model (EM)
Summary
The simplest extension of the free nucleon interactions to nuclear interactions is referred to as Single Particle Model (SPM) in the cosmic ray astrophysics literature [21, 28]. It assumes that in the photomeson regime the photon interacts always with one nucleon in the nucleus without affecting the rest of the nucleus (quasi-free interaction). The inelastic cross section is frequently assumed to scale with A, i.e. σAγ = Aσpγ, implying that dσjin→cli/dEi = Aj dσNinc→l i/dEi. The simplicity of the SPM allows estimating analytically the relative importance of photon-nucleon to photonuclear interactions in astrophysical scenarios.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
