CORSIKA 8 - Towards a modern framework for the simulation of extensive air showers

Current and future challenges in astroparticle physics require novel simulation tools to achieve higher precision and more flexibility. For three decades the FORTRAN version of CORSIKA served the community in an excellent way. However, the effort to maintain and further develop this complex package is getting increasingly difficult. To overcome existing limitations, and designed as a very open platform for all particle cascade simulations in astroparticle physics, we are developing CORSIKA 8 based on modern C++ and Python concepts. Here, we give a brief status report of the project.Comment: 4 pages, 3 figures; Proceedings of Ultra High Energy Cosmic Rays 201

The air shower simulation framework CORSIKA 8: Development and first applications to muon production

Tools to accurately simulate extensive air showers are a key asset for the understanding of ultra-high energy cosmic rays. In this thesis, the Monte Carlo air shower simulation framework CORSIKA 8 is presented. CORSIKA 8 constitutes a next-generation code that aims to combine new functionality with a high level of flexibility and modularity. Notable aspects include the ability to freely combine an arbitrary number of physical processes and to setup simulation environments consisting of several media, including custom atmospheric models. A special feature is the possibility to inspect the complete lineage of particles, which allows linking particles on ground with any of their preceding generations. After describing the foundations of Monte Carlo shower simulations, I explain the architecture of CORSIKA 8 in depth. Focusing on the hadronic and muonic shower components, results obtained with CORSIKA 8 and other simulation codes are compared with each other. Even when using the same hadronic interaction models, a number of differences are observed, in particular regarding low-energy interactions, which have a considerable impact on the lateral distribution of muons at kilometre-scale distances up to a factor of two and more. Making use of the lineage technique, I study the phase space of hadronic interactions in order to quantify the importance for muon production and compare the results with the Heitler–Matthews toy model. At high energies (√s ≳ 500 GeV) particle production in the forward region is confirmed to be especially important, while the central region becomes relevant at low energies (√s ≲ 50 GeV) in particular for muons at large distances. Additionally, I study the impact of modified hadronic interactions on air shower observables. Modified hadron-air cross-sections mainly affect the longitudinal development, causing a larger shift of the maximum muon production depth than of the shower maximum. Artificially increased ρ 0 production, on the other hand, can greatly increase the number of muons with only small impact on other observables. Finally, I also consider the possibility of large multiplicity boson production in the first interaction and study its phenomenology in air showers with a simple toy model. Within the scope of this thesis, I developed the foundations of the CORSIKA 8 framework. Based on the studies that have become possible with CORSIKA 8, I point out some new opportunities towards an improved understanding of muons in air showers

Air shower genealogy for muon production

Measurements of the muon content of extensive air showers at the highest energies show discrepancies compared to simulations as large as the differences between proton and iron. This so-called muon puzzle is commonly attributed to a lack of understanding of the hadronic interactions in the shower development. Furthermore, measurements of the fluctuations of muon numbers suggest that the discrepancy is likely a cumulative effect of interactions of all energies in the cascade. A feature of the air shower simulation code CORSIKA 8 allows us to access all previous generations of final-state muons up to the first interaction. With this technique, we study the influence of interactions happening at any intermediate stage in the cascade on muons depending on their lateral distance in a quantitative way and compare our results with predictions of the Heitler-Matthews model.Comment: 8 pages, 4 figures, proceedings of the 37th International Cosmic Ray Conference (ICRC 2021); v2: references update

Air shower genealogy for muon production

Measurements of the muon content of extensive air showers at the highest energies show discrepancies compared to simulations as large as the differences between proton and iron. This so-called muon puzzle is commonly attributed to a lack of understanding of the hadronic interactions in the shower development. Furthermore, measurements of the fluctuations of muon numbers suggest that the discrepancy is likely a cumulative effect of interactions of all energies in the cascade. A feature of the air shower simulation code CORSIKA 8 allows us to access all previous generations of final-state muons up to the first interaction. With this technique, we study the influence of interactions happening at any intermediate stage in the cascade on muons depending on their lateral distance in a quantitative way and compare our results with predictions of the Heitler-Matthews model.Comment: 8 pages, 4 figures, proceedings of the 37th International Cosmic Ray Conference (ICRC 2021); v2: references update

Pythia 8 as hadronic interaction model in air shower simulations

Hadronic interaction models are a core ingredient of simulations of extensive air showers and pose the major source of uncertainties of predictions of air shower observables. Recently, Pythia~8, a hadronic interaction model popular in accelerator-based high-energy physics, became usable in air shower simulations as well. We have integrated Pythia~8 with its new capabilities into the air shower simulation framework CORSIKA~8. First results show significantly shallower shower development, which we attribute to higher cross-section predictions by the new simplified nuclear model of Pythia.Comment: Proceedings of UHECR 202

Towards A Next Generation of CORSIKA: A Framework for the Simulation of Particle Cascades in Astroparticle Physics

A large scientific community depends on the precise modelling of complex processes in particle cascades in various types of matter. These models are used most prevalently in cosmic-ray physics, astrophysical-neutrino physics, and gamma-ray astronomy. In this white paper, we summarize the necessary steps to ensure the evolution and future availability of optimal simulation tools. The purpose of this document is not to act as a strict blueprint for next-generation software, but to provide guidance for the vital aspects of its design. The topics considered here are driven by physics and scientific applications. Furthermore, the main consequences of implementation decisions on performance are outlined. We highlight the computational performance as an important aspect guiding the design since future scientific applications will heavily depend on an efficient use of computational resources.Peer Reviewe

Pythia 8 as hadronic interaction model in air shower simulations

Hadronic interaction models are a core ingredient of simulations of extensive air showers and pose the major source of uncertainties of predictions of air shower observables. Recently, Pythia 8, a hadronic interaction model popular in accelerator-based high-energy physics, became usable in air shower simulations as well. We have integrated Pythia 8 with its new capabilities into the air shower simulation framework CORSIKA 8. First results show significantly shallower shower development, which we attribute to higher cross-section predictions by the new simplified nuclear model of Pythia