1 | \chapter{Physics Processes} |
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2 | |
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3 | \section{Design Philosophy} |
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4 | The processes category contains the implementations of particle transportation |
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5 | and physical interactions. All physics process conform to the basic interface |
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6 | {\it G4VProcess}, but different approaches have been developed for the |
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7 | detailed design of each sub-category. |
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8 | |
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9 | For the decay sub-category, the decays of all long-lived, unstable particles |
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10 | are handled by a single process. This process gets the step length from the |
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11 | mean life of the particle. The generation of decay products requires a |
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12 | knowledge of the branching ratios and/or data distributions stored in the |
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13 | particle class. |
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14 | |
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15 | The electromagnetic sub-category is divided further into the following |
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16 | packages: |
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17 | \begin{itemize} |
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18 | \item {\it standard}: handling basic properties for electron, positron, |
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19 | photon and hadron interactions, |
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20 | \item {\it low energy}: providing alternative models extended down to lower |
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21 | energies than the standard package, |
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22 | \item {\it muons}: handling muon interactions, |
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23 | \item {\it x-rays}: providing specific code for x-ray physics, |
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24 | \item {\it optical}: providing specific code for optical photons, |
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25 | \item {\it utils}: collecting utility classes used by the above packages. |
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26 | \end{itemize} |
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27 | It provides the features of openness and extensibilty resulting from the use |
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28 | of object-oriented technology; alternative physics models, obeying the same |
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29 | process abstract interface, are often available for a given type of |
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30 | interaction. |
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31 | |
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32 | For hadronic physics, an additional set of implementation frameworks was |
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33 | added to accommodate the large number of possible modeling approaches. |
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34 | The top-level framework provides the basic interface to other {\sc Geant4} |
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35 | categories. It satisfies the most general use-case for hadronic shower |
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36 | simulations, namely to provide inclusive cross sections and final state |
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37 | generation. The frameworks are then refined for increasingly specific |
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38 | use-cases, building a hierarchy in which each level implements the |
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39 | interface specified by the level above it. A given hadronic process may |
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40 | be implemented at any one of these levels. For example, the process |
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41 | may be implemented by one of several models, and each of the models may |
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42 | in turn be implemented by several sub-models at the lower framework levels. |
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43 | |
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44 | \section{Class Design} |
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45 | |
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46 | \subsection{General} |
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47 | The object-oriented design of the generic physics process G4VProcess and its |
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48 | relation to the process manager is shown in |
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49 | Fig. \ref{figure:physics-1}. Fig. \ref{figure:physics-2} shows how specific |
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50 | physics processes are related to G4VProcess. |
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51 | |
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52 | \vspace{10pt} |
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53 | \begin{figure}[!ht] |
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54 | \begin{center} |
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55 | \includegraphics[angle=0,scale=0.6]{OOAnalysisDesign/PhysicsProcesses/classDgmProcessMain.eps} |
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56 | \caption{Management of Physics Processes} |
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57 | \label{figure:physics-1} |
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58 | \end{center} |
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59 | \end{figure} |
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60 | |
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61 | \vspace{10pt} |
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62 | \begin{figure}[!ht] |
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63 | \begin{center} |
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64 | \includegraphics[angle=0,scale=0.6]{OOAnalysisDesign/PhysicsProcesses/classDgmProcessProcesses.eps} |
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65 | \caption{General Physics Processes} |
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66 | \label{figure:physics-2} |
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67 | \end{center} |
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68 | \end{figure} |
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69 | |
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70 | |
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71 | % Class diagrams of the low energy electromagnetic processes and the hadronic |
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72 | % models are shown in Fig. (not yet available) |
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73 | % Figs. \ref{figure:emlep-1} |
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74 | % and Fig. \ref{figure:hadp-1}, |
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75 | % respectively. |
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76 | |
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77 | % \begin{figure} |
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78 | % \begin{center} |
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79 | % \centerline{\includegraphics[angle=270,scale=0.5]{OOAnalysisDesign/PhysicsProcesses/ElectroMagnetic/classDgmLowEnergyProc.ps}} |
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80 | % \vspace{10pt} |
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81 | % \caption{Low Energy Electromagnetic Processes} |
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82 | % \label{figure:emlep-1} |
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83 | % \end{center} |
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84 | % \end{figure} |
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85 | |
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86 | % \begin{figure} |
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87 | % \begin{center} |
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88 | % \includegraphics[angle=270,scale=0.45]{OOAnalysisDesign/PhysicsProcesses/Hadronic/classDgmHadronicModels.ps} |
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89 | % \caption{Hadronic Processes} |
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90 | % \label{figure:hadp-1} |
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91 | % \end{center} |
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92 | % \end{figure} |
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93 | |
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94 | \section{Status of this chapter} |
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95 | |
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96 | 27.06.05 section on design philosophy added by D.H. Wright \\ |
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