Geant4 Tutorial: Particle Types and Macro File Usage

Geant4 Tutorial: Particle Types and Macro File Usage

🎓 Geant4 Training Series – Particle Definitions and Macro File Syntax

In this part of the Geant4 training series by Partoyar Academy, we explore one of the most fundamental aspects of Monte Carlo simulations: particles in Geant4. Understanding the classification of particles and how to define them in macro files is the first step toward building a successful simulation.

🧪 Particle Categories in Geant4

Geant4 provides a wide range of predefined particles, including elementary particles, composite particles, ions, and even virtual test particles. Here's a breakdown of the main categories:

1. Leptons

Light particles with no strong interaction:

• Electron: e-

• Positron: e+

• Muons: mu-, mu+

• Neutrinos: nu_e, nu_mu, nu_tau

2. Photons

Massless, chargeless particles:

• Gamma photon: gamma

• Optical photon: opticalphoton

3. Mesons

Medium-mass composite particles:

• Pions: pi+, pi-, pi0

• Kaons: K+, K-, K0

4. Baryons

Heavier particles like:

• Proton: proton

• Neutron: neutron

• Antiproton, antineutron, and other baryons

5. Ions

Atomic nuclei with specific charge:

• Defined using the /gun/ion command

6. Test and Virtual Particles

Used for geometry testing without physical interaction:

• geantino

• chargedgeantino

📄 How to Define Particles in Geant4 Macro Files

Macro files (with .mac extension) allow users to run simulations without writing C++ code. To specify a particle type, use:

/gun/particle [particle_name]

For ions, use the extended syntax:

/gun/particle ion
/gun/ion [Z] [A] [Q] [E]

Example: Nitrogen-14 ion with charge +1 and energy 100 MeV:

/gun/particle ion
/gun/ion 7 14 1 100 MeV

📊 Particle Name Table for Macro Files

✅ Summary

Mastering particle definitions and macro syntax is a foundational skill for any Geant4 user. This tutorial, part of the Partoyar Academy’s Geant4 series, helps you build more accurate, reliable, and scalable simulations.