Physics Lists for Particle Physics

Introduction

Given the toolkit nature of Geant4, a choice of physics processes is available. The choices offer either different detail of physics modeling or different physics modeling descriptions. It is the choice of the user to decide how much detail in the physics modeling is needed, weighing the detail against cpu performance. A user can construct his own physics list, or use one of the physics lists offered below, or modify any of the offered physics lists.

Reference Physics Lists

Please see the detailed description for a full description of all reference physics lists including our current understanding of physics performance. The reference physics lists are part of the Geant4 source code and are distributed as an integral part of Geant4 source code from the Geant4 download area. Physics lists include those originally named 'educated guess physics lists'. Nearly all these lists are suitable for all primary particles and for a wide range of energies. There are four families of lists:

LHEP or parameterised modeling of hadronic interactions.
QGS, or lists based on a modeling using Quark Gluon String model for high energy hadronic interactions of protons, neutrons, pions, and Kaons.
FTF, or lists based on a modeling using the FTF model for high energy hadronic interactions of protons, neutrons, pions, and Kaons; FTF is FRITIOF like string model.
several more specialised lists.

All of the lists in the first three families share components to attach certain types of processes to groups of particles. The classes of components are:

electromagnetic interactions for all particles and electromagnetic processes for leptons and gammas. Three different settings are offered
- the default setting using standard parameters tuned for best physics performance
- using parameters optimised for better CPU performance at the cost slightly less precise physics. This is identified in physics lists by the extension _EMV.
- a set of experimental parameters, used by physics lists with the extension _EMX
Inelastic interactions for hadrons
Elastic scattering of hadrons off nuclei
Capture at rest for negative charged hadrons and muons
Decay of unstable particles in flight and at rest
Optional specialised treatment of low energy neutrons ( < 20MeV); these lists have an _HP extension.