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