pyTRAIN -- a modern TRAIN implementation
Abstract
The TRAIN code, developed in 1995 as a post-processor for second-order transport maps from MAD, has been used extensively at the LEP and the LHC to study self-consistent closed orbits, tunes and chromaticities of bunch trains under the presence of beam-beam long-range (BBLR) and PACMAN effects.. This paper presents a modern re-implementation of the TRAIN concept in Python using well-known numeric libraries (numpy, scipy) and an optional link to MAD-X via cpymad. This greatly improves the usability, maintainability and extensibility of the code. New functionality includes the support for arbitrary particle types, an arbitrary number and distribution of beam-beam interaction points, and the extrapolation of the beam-beam induced closed-orbit effects to arbitrary points in the machine. The code is benchmarked against the classic TRAIN code, and simulation results are compared to observations from LHC physics operation.
Cite
@article{arxiv.2604.18466,
title = {pyTRAIN -- a modern TRAIN implementation},
author = {Michi Hostettler and Xavier Buffat and Tobias Persson and Tatiana Pieloni and Jorg Wenninger},
journal= {arXiv preprint arXiv:2604.18466},
year = {2026}
}
Comments
Presented at the ICFA mini workshop: Beam-Beam Effects in Circular Colliders BB24 (September 2024, Lausanne, Switzerland)