1. Introduction

The QWeak simulation package QweakSimG4 is a collection of C++ classes that can be compiled and run for the purpose of physics process simulation in the experiment. The code aims to eventually include all objects and properties found in the current design of the QWeak experiment, as well as most physics processes that are expected to emerge during the experiment. The implementation of these objects and properties is at various stages of development, the detail of which is indicated in the extent of the list of contents. The code is based on the GEANT4 ¹ simulation code [1] and the ROOT² analysis package and requires these to compile.

The purpose of this manual is to describe the classes and their routines and how they are used in the simulation. The manual is supposed to enable other people to extend, repair or otherwise change the QWeak simulation program to suit their purposes. Most importantly, it is meant to document the algorithms used in implementing the physical processes in the simulation, in as far as they go beyond what is implemented in GEANT4 itself and adequately described in its manual. The detail with which the code is described will be evolving over time. Please make sure that you consult the most recent version before contacting us with questions. If you cannot find the answer to your problem in here, you can contact us at

grimm@jlab.org or mgericke@jlab.org.

A few points to consider before using this manual are that, (1) we do not (can not) spent much time here, explaining any details regarding the usage of the ROOT or GEANT4 packages and its class libraries. So you should be or become acquainted with (most) aspects of the packages before trying to make any serious changes. You can find details about ROOT and GEANT4 from their websites and the ROOT manual itself [2]. Also, (2) this library is intended to work for \textit{Linux} only. We have made no attempt to make this run on Windows or Mac.

QWeak Geant4 Simulation Setup

1.1 This manual is organized as follows:

The first chapter consists of very general information, such as a list of class names and their current status or level of usage in the simulation, the compile requirements such as the structure of the \textit{Makefile} and where the source files have to be located with respect to each other, environment variable definitions, etc.. In other words, this portion of the document should be enough to compile the simulation as it stands, provided that both ROOT and GEANT4 have been installed properly. The second chapter provides a detailed description of the event generator used in the simulations and attempts to give a detailed explanation of the physics processes included. The following chapters (one for each class) provide a detailed reference explaining what the classes do, how they do it and how to use the routines to access the class members, change variables, etc.. This portion is necessary for someone who actually wants to change the code. The details about the implementation of the physics processes used in the simulation are given together with its code in the appropriate chapters.

¹ http://geant4.cern.ch/index.shtml ⇑