| 1 | <HTML> |
|---|
| 2 | <HEAD> |
|---|
| 3 | <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"> |
|---|
| 4 | <META NAME="GENERATOR" CONTENT="Mozilla/4.04 [en] (X11; I; AIX 4.1) [Netscape]"> |
|---|
| 5 | </HEAD> |
|---|
| 6 | |
|---|
| 7 | <BODY> |
|---|
| 8 | <!-- Created by: Makoto Asai, 14-Apr-2003 --> |
|---|
| 9 | |
|---|
| 10 | <BR> |
|---|
| 11 | |
|---|
| 12 | <TABLE WIDTH="100%" > |
|---|
| 13 | <TR> |
|---|
| 14 | <TD> |
|---|
| 15 | |
|---|
| 16 | </A> |
|---|
| 17 | <A HREF="index.html"> |
|---|
| 18 | <IMG SRC="../../../../resources/html/IconsGIF/Contents.gif" ALT="Contents" HEIGHT=16 WIDTH=59></A> |
|---|
| 19 | <A HREF="thresholdVScut.html"> |
|---|
| 20 | <IMG SRC="../../../../resources/html/IconsGIF/Previous.gif" ALT="Previous" HEIGHT=16 WIDTH=59></A> |
|---|
| 21 | <A HREF="physicsTable.html"> |
|---|
| 22 | <IMG SRC="../../../../resources/html/IconsGIF/Next.gif" ALT="Next" HEIGHT=16 WIDTH=59></A> |
|---|
| 23 | </TD> |
|---|
| 24 | <P> |
|---|
| 25 | |
|---|
| 26 | <TD ALIGN=RIGHT><FONT COLOR="#238E23"><FONT SIZE=-1> |
|---|
| 27 | <B>Geant4 User's Guide</B></FONT></FONT> |
|---|
| 28 | <BR><FONT COLOR="#238E23"><FONT SIZE=-1> |
|---|
| 29 | <B>For Application Developers</B></FONT></FONT> |
|---|
| 30 | <BR><FONT COLOR="#238E23"><FONT SIZE=-1> |
|---|
| 31 | <B>Tracking and Physics</B></FONT></FONT></TD> |
|---|
| 32 | </TR> |
|---|
| 33 | </TABLE> |
|---|
| 34 | <P><BR> |
|---|
| 35 | |
|---|
| 36 | <CENTER><FONT COLOR="#238E23"><FONT SIZE=+3> |
|---|
| 37 | <B>5.5 Cuts per Region</B></FONT></FONT> |
|---|
| 38 | </CENTER> |
|---|
| 39 | <P><BR> |
|---|
| 40 | |
|---|
| 41 | <HR ALIGN="Center" SIZE="7%"> |
|---|
| 42 | <P> |
|---|
| 43 | |
|---|
| 44 | <a name="5.5.1"> |
|---|
| 45 | <H2>5.5.1 General Concepts</H2></a> |
|---|
| 46 | Beginning with Geant4 version 5.1, the concept of a region has been defined |
|---|
| 47 | for use in geometrical descriptions. Details about regions and how to use |
|---|
| 48 | them are available in |
|---|
| 49 | <a href="../Detector/geometry.html#4.1.3.1">subsection 4.1.3.1</a>. |
|---|
| 50 | As an example, suppose a user defines three regions, corresponding to the |
|---|
| 51 | tracking volume, the calorimeter and the bulk structure of a detector. |
|---|
| 52 | For performance reasons, the user may not be interested in the detailed |
|---|
| 53 | development of electromagnetic showers in the insensitive bulk structure, |
|---|
| 54 | but wishes to maintain the best possible accuracy in the tracking region. |
|---|
| 55 | In such a use case, Geant4 allows the user to set different production |
|---|
| 56 | thresholds ("cuts") for each geometrical region. This ability, referred to as |
|---|
| 57 | "cuts per region", is also a new feature provided by the Geant4 5.1 release. |
|---|
| 58 | The general concepts of production thresholds were presented in the |
|---|
| 59 | <a href="thresholdVScut.html">previous section</a>. |
|---|
| 60 | <p> |
|---|
| 61 | Please note that this new feature is intended only for users who |
|---|
| 62 | <ol> |
|---|
| 63 | <li>are simulating the most complex geometries, such as an LHC detector, and |
|---|
| 64 | <li>are experienced in simulating electromagnetic showers in matter. |
|---|
| 65 | </ol> |
|---|
| 66 | We strongly recommend that results generated with this new feature be compared |
|---|
| 67 | with results using the same geometry and uniform production thresholds. |
|---|
| 68 | Setting completely different cut values for individual regions may break the |
|---|
| 69 | coherent and comprehensive accuracy of the simulation. Therefore cut values |
|---|
| 70 | should be carefully optimized, based on a comparison with results obtained |
|---|
| 71 | using uniform cuts. |
|---|
| 72 | |
|---|
| 73 | <P> |
|---|
| 74 | |
|---|
| 75 | <HR> |
|---|
| 76 | <a name="5.5.2"> |
|---|
| 77 | <H2>5.5.2 Default Region</H2></a> |
|---|
| 78 | The world volume is treated as a region by default. A <i>G4Region</i> object |
|---|
| 79 | is automatically assigned to the world volume and is referred to as the |
|---|
| 80 | "default region". The production cuts for this region are the defaults |
|---|
| 81 | which are defined in the <i>UserPhysicsList</i>. Unless the user defines |
|---|
| 82 | different cut values for other regions, the cuts in the default region will be |
|---|
| 83 | used for the entire geometry. |
|---|
| 84 | <p> |
|---|
| 85 | Please note that the default region and its default production cuts are |
|---|
| 86 | created and set automatically by <i>G4RunManager</i>. The user is <b>not</b> |
|---|
| 87 | allowed to set a region to the world volume, <b>nor</b> to assign other |
|---|
| 88 | production cuts to the default region. |
|---|
| 89 | |
|---|
| 90 | <P> |
|---|
| 91 | |
|---|
| 92 | <HR> |
|---|
| 93 | <a name="5.5.3"> |
|---|
| 94 | <H2>5.5.3 Assigning Production Cuts to a Region</H2></a> |
|---|
| 95 | In the <tt>SetCuts()</tt> method of the user's physics list, the user must |
|---|
| 96 | first define the default cuts. Then a <i>G4ProductionCuts</i> object must be |
|---|
| 97 | created and initialized with the cut value desired for a given region. This |
|---|
| 98 | object must in turn be assigned to the region object, which can be accessed by |
|---|
| 99 | name from the <i>G4RegionStore</i>. An example <tt>SetCuts()</tt> code |
|---|
| 100 | follows. |
|---|
| 101 | |
|---|
| 102 | <p> |
|---|
| 103 | <center> |
|---|
| 104 | <table border=2 cellpadding=10> |
|---|
| 105 | <tr> |
|---|
| 106 | <td> |
|---|
| 107 | <pre> |
|---|
| 108 | void MyPhysicsList::SetCuts() |
|---|
| 109 | { |
|---|
| 110 | // default production thresholds for the world volume |
|---|
| 111 | SetCutsWithDefault(); |
|---|
| 112 | |
|---|
| 113 | // Production thresholds for detector regions |
|---|
| 114 | G4Region* region; |
|---|
| 115 | G4String regName; |
|---|
| 116 | G4ProductionCuts* cuts; |
|---|
| 117 | |
|---|
| 118 | regName = "tracker"; |
|---|
| 119 | region = G4RegionStore::GetInstance()->GetRegion(regName); |
|---|
| 120 | cuts = new G4ProductionCuts; |
|---|
| 121 | cuts->SetProductionCut(0.01*mm); // same cuts for gamma, e- and e+ |
|---|
| 122 | region->SetProductionCuts(cuts); |
|---|
| 123 | |
|---|
| 124 | regName = "calorimeter"; |
|---|
| 125 | region = G4RegionStore::GetInstance()->GetRegion(regName); |
|---|
| 126 | cuts = new G4ProductionCuts; |
|---|
| 127 | cuts->SetProductionCut(0.01*mm,G4ProductionCuts::GetIndex("gamma")); |
|---|
| 128 | cuts->SetProductionCut(0.1*mm,G4ProductionCuts::GetIndex("e-")); |
|---|
| 129 | cuts->SetProductionCut(0.1*mm,G4ProductionCuts::GetIndex("e+")); |
|---|
| 130 | region->SetProductionCuts(cuts); |
|---|
| 131 | } |
|---|
| 132 | </pre> |
|---|
| 133 | </td> |
|---|
| 134 | </tr> |
|---|
| 135 | <tr> |
|---|
| 136 | <td align=center> |
|---|
| 137 | Source listing 5.5.1 <br> |
|---|
| 138 | <tt>Setting production cuts to a region</tt> |
|---|
| 139 | </td> |
|---|
| 140 | </tr> |
|---|
| 141 | </table></center> |
|---|
| 142 | <p> |
|---|
| 143 | |
|---|
| 144 | <BR><BR> |
|---|
| 145 | <HR><A HREF="../../../../Authors/html/subjectsToAuthors.html"> |
|---|
| 146 | <I>About the authors</A></I> |
|---|
| 147 | </BODY> |
|---|
| 148 | </HTML> |
|---|
