Chromo: A High-Performance Python Interface to Hadronic Event Generators for Collider and Cosmic-Ray Simulations

TL;DR

Chromo is a high-performance Python interface that unifies access to multiple hadronic event generators, enabling efficient and flexible simulations for collider and cosmic-ray physics within the Python ecosystem.

Contribution

It introduces a unified, zero-overhead Python interface to several hadronic event generators, simplifying integration and analysis in scientific workflows.

Findings

Supports multiple generators with minimal performance overhead

Enables easy installation and integration with scientific Python tools

Facilitates event export and manipulation for advanced simulations

Abstract

Simulations of hadronic and nuclear interactions are essential in both collider and astroparticle physics. The Chromo package provides a unified Python interface to multiple widely used hadronic event generators, including EPOS, DPMJet, Sibyll, QGSJet, and Pythia. Built on top of their original Fortran and C++ implementations, Chromo offers a zero-overhead abstraction layer suitable for use in Python scripts, Jupyter notebooks, or from the command line, while preserving the performance of direct calls to the generators. It is easy to install via precompiled binary wheels distributed through PyPI, and it integrates well with the Scientific Python ecosystem. Chromo supports event export in HepMC, ROOT, and SVG formats and provides a consistent interface for inspecting, filtering, and modifying particle collision events. This paper describes the architecture, typical use cases, and performance characteristics of Chromo and its role in contemporary astroparticle simulations, such as in the MCEq cascade solver.