A comprehensive guide to the physics and usage of PYTHIA 8.3

TL;DR

This manual provides a detailed overview of PYTHIA 8.3, a widely used event generator in particle physics, covering its physics models, algorithms, and practical usage for simulating high-energy collisions.

Contribution

It offers an in-depth description of the physics models, algorithms, and user guidance for PYTHIA 8.3, facilitating accurate simulation and further development in particle physics research.

Findings

Comprehensive description of PYTHIA 8.3 physics models

Detailed algorithms enabling independent reproduction of results

Pedagogical examples and user interface guidance

Abstract

This manual describes the PYTHIA 8.3 event generator, the most recent version of an evolving physics tool used to answer fundamental questions in particle physics. The program is most often used to generate high-energy-physics collision "events", i.e. sets of particles produced in association with the collision of two incoming high-energy particles, but has several uses beyond that. The guiding philosophy is to produce and reproduce properties of experimentally obtained collisions as accurately as possible. The program includes a wide ranges of reactions within and beyond the Standard Model, and extending to heavy ion physics. Emphasis is put on phenomena where strong interactions play a major role. The manual contains both pedagogical and practical components. All included physics models are described in enough detail to allow the user to obtain a cursory overview of used assumptions and approximations, enabling an informed evaluation of the program output. A number of the most central algorithms are described in enough detail that the main results of the program can be reproduced independently, allowing further development of existing models or the addition of new ones. Finally, a chapter dedicated fully to the user is included towards the end, providing pedagogical examples of standard use cases, and a detailed description of a number of external interfaces. The program code, the online manual, and the latest version of this print manual can be found on the PYTHIA web page: https://www.pythia.org/