| 1 | <html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>5.5. Cuts per Region</title><link rel="stylesheet" href="../xml/XSLCustomizationLayer/G4HTMLStylesheet.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.71.1"><link rel="start" href="index.html" title="Geant4 User's Guide for Application Developers"><link rel="up" href="ch05.html" title="Chapter 5. Tracking and Physics"><link rel="prev" href="ch05s04.html" title="5.4. Production Threshold versus Tracking Cut"><link rel="next" href="ch05s06.html" title="5.6. Physics Table"><script language="JavaScript">
|
|---|
| 2 | function remote_win(fName)
|
|---|
| 3 | {
|
|---|
| 4 | var url = "AllResources/Detector/geometry.src/" + fName;
|
|---|
| 5 | RemoteWin=window.open(url,"","resizable=no,toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=0,copyhistory=0,width=520,height=520")
|
|---|
| 6 | RemoteWin.creator=self
|
|---|
| 7 | }
|
|---|
| 8 | </script></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">5.5.
|
|---|
| 9 | Cuts per Region
|
|---|
| 10 | </th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ch05s04.html"><img src="AllResources/IconsGIF/prev.gif" alt="Prev"></a> </td><th width="60%" align="center">Chapter 5.
|
|---|
| 11 | Tracking and Physics
|
|---|
| 12 | </th><td width="20%" align="right"> <a accesskey="n" href="ch05s06.html"><img src="AllResources/IconsGIF/next.gif" alt="Next"></a></td></tr></table><hr></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="sect.CutReg"></a>5.5.
|
|---|
| 13 | Cuts per Region
|
|---|
| 14 | </h2></div></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="sect.CutReg.Gene"></a>5.5.1.
|
|---|
| 15 | General Concepts
|
|---|
| 16 | </h3></div></div></div><p>
|
|---|
| 17 | Beginning with Geant4 version 5.1, the concept of a region has been
|
|---|
| 18 | defined for use in geometrical descriptions. Details about regions
|
|---|
| 19 | and how to use them are available in
|
|---|
| 20 | <a href="ch04.html#sect.Geom.LogVol.SubReg" title="4.1.3.1.
|
|---|
| 21 | Sub-detector Regions
|
|---|
| 22 | ">Section 4.1.3.1</a>.
|
|---|
| 23 | As an example, suppose a user defines three regions, corresponding to
|
|---|
| 24 | the tracking volume, the calorimeter and the bulk structure of a
|
|---|
| 25 | detector. For performance reasons, the user may not be interested
|
|---|
| 26 | in the detailed development of electromagnetic showers in the
|
|---|
| 27 | insensitive bulk structure, but wishes to maintain the best
|
|---|
| 28 | possible accuracy in the tracking region. In such a use case,
|
|---|
| 29 | Geant4 allows the user to set different production thresholds
|
|---|
| 30 | ("cuts") for each geometrical region. This ability, referred to as
|
|---|
| 31 | "cuts per region", is also a new feature provided by the Geant4 5.1
|
|---|
| 32 | release. The general concepts of production thresholds were
|
|---|
| 33 | presented in the <a href="ch05s04.html" title="5.4.
|
|---|
| 34 | Production Threshold versus Tracking Cut
|
|---|
| 35 | ">Section 5.4</a>.
|
|---|
| 36 | </p><p>
|
|---|
| 37 | Please note that this new feature is intended only for users
|
|---|
| 38 | who
|
|---|
| 39 |
|
|---|
| 40 | </p><div class="orderedlist"><ol type="1" compact><li><p>
|
|---|
| 41 | are simulating the most complex geometries, such as an LHC
|
|---|
| 42 | detector, and
|
|---|
| 43 | </p></li><li><p>
|
|---|
| 44 | are experienced in simulating electromagnetic showers in
|
|---|
| 45 | matter.
|
|---|
| 46 | </p></li></ol></div><p>
|
|---|
| 47 | </p><p>
|
|---|
| 48 | We strongly recommend that results generated with this new feature
|
|---|
| 49 | be compared with results using the same geometry and uniform
|
|---|
| 50 | production thresholds. Setting completely different cut values for
|
|---|
| 51 | individual regions may break the coherent and comprehensive
|
|---|
| 52 | accuracy of the simulation. Therefore cut values should be
|
|---|
| 53 | carefully optimized, based on a comparison with results obtained
|
|---|
| 54 | using uniform cuts.
|
|---|
| 55 | </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="sect.CutReg.DefReg"></a>5.5.2.
|
|---|
| 56 | Default Region
|
|---|
| 57 | </h3></div></div></div><p>
|
|---|
| 58 | The world volume is treated as a region by default. A
|
|---|
| 59 | <span class="emphasis"><em>G4Region</em></span> object is automatically assigned to the world
|
|---|
| 60 | volume and is referred to as the "default region". The production
|
|---|
| 61 | cuts for this region are the defaults which are defined in the
|
|---|
| 62 | <span class="emphasis"><em>UserPhysicsList</em></span>. Unless the user defines different cut
|
|---|
| 63 | values for other regions, the cuts in the default region will be
|
|---|
| 64 | used for the entire geometry.
|
|---|
| 65 | </p><p>
|
|---|
| 66 | Please note that the default region and its default production
|
|---|
| 67 | cuts are created and set automatically by <span class="emphasis"><em>G4RunManager</em></span>.
|
|---|
| 68 | The user is <span class="bold"><strong>not</strong></span> allowed to set a region to
|
|---|
| 69 | the world volume, <span class="bold"><strong>nor</strong></span> to assign other
|
|---|
| 70 | production cuts to the default region.
|
|---|
| 71 | </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="sect.CutReg.Assig"></a>5.5.3.
|
|---|
| 72 | Assigning Production Cuts to a Region
|
|---|
| 73 | </h3></div></div></div><p>
|
|---|
| 74 | In the <code class="literal">SetCuts()</code> method of the user's physics list, the
|
|---|
| 75 | user must first define the default cuts. Then a
|
|---|
| 76 | <span class="emphasis"><em>G4ProductionCuts</em></span> object must be created and initialized with
|
|---|
| 77 | the cut value desired for a given region. This object must in turn
|
|---|
| 78 | be assigned to the region object, which can be accessed by name
|
|---|
| 79 | from the <span class="emphasis"><em>G4RegionStore</em></span>. An example <code class="literal">SetCuts()</code>
|
|---|
| 80 | code follows.
|
|---|
| 81 |
|
|---|
| 82 | </p><div class="example"><a name="programlist_CutReg_1"></a><p class="title"><b>Example 5.12.
|
|---|
| 83 | <code class="literal">Setting production cuts to a region</code>
|
|---|
| 84 | </b></p><div class="example-contents"><pre class="programlisting">
|
|---|
| 85 | void MyPhysicsList::SetCuts()
|
|---|
| 86 | {
|
|---|
| 87 | // default production thresholds for the world volume
|
|---|
| 88 | SetCutsWithDefault();
|
|---|
| 89 |
|
|---|
| 90 | // Production thresholds for detector regions
|
|---|
| 91 | G4Region* region;
|
|---|
| 92 | G4String regName;
|
|---|
| 93 | G4ProductionCuts* cuts;
|
|---|
| 94 |
|
|---|
| 95 | regName = "tracker";
|
|---|
| 96 | region = G4RegionStore::GetInstance()->GetRegion(regName);
|
|---|
| 97 | cuts = new G4ProductionCuts;
|
|---|
| 98 | cuts->SetProductionCut(0.01*mm); // same cuts for gamma, e- and e+
|
|---|
| 99 | region->SetProductionCuts(cuts);
|
|---|
| 100 |
|
|---|
| 101 | regName = "calorimeter";
|
|---|
| 102 | region = G4RegionStore::GetInstance()->GetRegion(regName);
|
|---|
| 103 | cuts = new G4ProductionCuts;
|
|---|
| 104 | cuts->SetProductionCut(0.01*mm,G4ProductionCuts::GetIndex("gamma"));
|
|---|
| 105 | cuts->SetProductionCut(0.1*mm,G4ProductionCuts::GetIndex("e-"));
|
|---|
| 106 | cuts->SetProductionCut(0.1*mm,G4ProductionCuts::GetIndex("e+"));
|
|---|
| 107 | region->SetProductionCuts(cuts);
|
|---|
| 108 | }
|
|---|
| 109 | </pre></div></div><p><br class="example-break">
|
|---|
| 110 | </p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ch05s04.html"><img src="AllResources/IconsGIF/prev.gif" alt="Prev"></a> </td><td width="20%" align="center"><a accesskey="u" href="ch05.html"><img src="AllResources/IconsGIF/up.gif" alt="Up"></a></td><td width="40%" align="right"> <a accesskey="n" href="ch05s06.html"><img src="AllResources/IconsGIF/next.gif" alt="Next"></a></td></tr><tr><td width="40%" align="left" valign="top">5.4.
|
|---|
| 111 | Production Threshold versus Tracking Cut
|
|---|
| 112 | </td><td width="20%" align="center"><a accesskey="h" href="index.html"><img src="AllResources/IconsGIF/home.gif" alt="Home"></a></td><td width="40%" align="right" valign="top"> 5.6.
|
|---|
| 113 | Physics Table
|
|---|
| 114 | </td></tr></table></div></body></html>
|
|---|
