Jan Ebr, Jakub Vícha, and Jiří Blažek from the Department of Astroparticle Physics at the Institute of Physics of the Czech Academy of Sciences contributed to an article published recently in Nature Reviews Physics. The article deals with the topic of tuning event generators, which are computer programs that simulate particle collisions according to a theoretical model and generate hypothetical data that would correspond to real experiments on accelerators.
In this article, scientists from the Institute of Physics of the Czech Academy of Sciences make a significant contribution to the topic of how modifications to models of collisions between primary particles such as protons, neutrons, and atomic nuclei (known as hadrons) might look. Thanks to their experience from the MOCHI (Modified Characteristics of Hadronic Interactions) project, they are able to modify models and observe what the predictions of the modified models are for events observed in cosmic rays. In addition to modifying models, scientists at the Institute of Physics are also able to look for ways to change model predictions so that they agree with the data. For example, Jakub Vícha (head of the hadronic interactions group at the Pierre Auger Observatory in Argentina) used data from the Pierre Auger Observatory for two specific predictions – a shift in shower depth and a change in the number of muons on Earth.
The article in Nature Reviews Physics is the outcome of a workshop held last year in Wuppertal. The aim of the workshop was to find a way to use data from astroparticle experiments at observatories to improve simulation codes used to simulate collisions between elementary particles. These codes are currently based largely on information from particle accelerators (e.g., the LHC), which provide a large amount of detailed data on what happens during collisions. Because a single collision can create hundreds of other particles, this information is very diverse. At observatories such as the Pierre Auger Observatory, we can observe particles with energies up to three orders of magnitude higher. However, we are unable to observe the collisions and the hundreds of particles created directly; we can only see their consequences several generations of particles later. These observatories therefore provide us with only very indirect information about the collisions themselves.
The workshop featured a discussion on various methods of using information from observatories to improve models at energies higher than those achieved in accelerators. The discussion was attended by experts in accelerator experiments, astroparticle physics, and scientists involved in tuning—that is, using statistical methods to make models work as well as possible based on available data.
The workshop resulted in an article providing an overview of the latest event generators and their tuning, including the most relevant inputs from high-energy accelerator experiments and astroparticle experiments. The authors also present a plan that shows for the first time how to perform unified tuning of event generators with data from accelerator and astroparticle experiments.
The workshop was organized by the University of Dortmund and, in addition to scientists from the Institute of Physics of the Czech Academy of Sciences, was attended by experts from the universities of Wuppertal or Frankfurt, from CERN and other research institutions.
Nature Reviews Physics is a prestigious scientific monthly published by Nature Portfolio. Its impact factor (a key indicator of its prestige and influence in the field) was 36.273 in 2021.
Albrecht, J., Becker Tjus, J., Behling, N. et al. (from FZU: J. Ebr, J. Blažek, J. Vícha): Global tuning of hadronic interaction models with accelerator-based and astroparticle data. Nature Review Physics (2025). doi: 10.1038/s42254-025-00897-3