| 1 | <html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>FAQ.5. Physics and cuts</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="ch10.html" title="Chapter FAQ. Frequentry Asked Questions"><link rel="prev" href="ch10s04.html" title="FAQ.4. Tracks and steps"><link rel="next" href="ch10s06.html" title="FAQ.6. Visualization"><script language="JavaScript">
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| 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">FAQ.5.
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| 9 | Physics and cuts
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| 10 | </th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ch10s04.html"><img src="AllResources/IconsGIF/prev.gif" alt="Prev"></a> </td><th width="60%" align="center">Chapter FAQ.
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| 11 | Frequentry Asked Questions
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| 12 | </th><td width="20%" align="right"> <a accesskey="n" href="ch10s06.html"><img src="AllResources/IconsGIF/next.gif" alt="Next"></a></td></tr></table><hr></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="qanda.PhysicsCuts"></a>FAQ.5.
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| 13 | Physics and cuts
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| 14 | </h2></div></div></div><div class="qandaset"><table border="0" summary="Q and A Set"><col align="left" width="1%"><tbody><tr class="question"><td align="left" valign="top"><a name="qanda.PhysicsCuts.HowProdCuts"></a><a name="id554957"></a><b>Q:</b></td><td align="left" valign="top"><p>
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| 15 | How do production cuts (in range) work in Geant4 ? Are they also used
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| 16 | in tracking ? If a particle has an energy lower than the converted cut
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| 17 | in energy for the given material and the distance to the next boundary
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| 18 | is smaller than the cut in range, is the particle killed ?
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| 19 | </p></td></tr><tr class="answer"><td align="left" valign="top"><b>A:</b></td><td align="left" valign="top"><p>
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| 20 | Geant4 does <span class="bold"><strong>NOT</strong></span> have a "tracking cut".
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| 21 | The toolkit's default behaviour is to track particles down to zero range
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| 22 | (i.e. zero energy). Of course, it is possible for the user to create and
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| 23 | register a process that kills particles below a certain energy or range;
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| 24 | this is however <span class="bold"><strong>NOT</strong></span> provided by default
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| 25 | in Geant4. So there's <span class="bold"><strong>NO</strong></span> "tracking cut".
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| 26 | For example, suppose a particle that is nearing zero energy will at some
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| 27 | point be proposed by its Ionisation process to undergo one final step,
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| 28 | from its current energy down to zero energy. This is still only a
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| 29 | proposal. If during this step the particle crosses a boundary, then the
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| 30 | transportation will limit the step at a length smaller than the
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| 31 | Ionisation -- so the particle will still see and cross the relevant
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| 32 | boundary, and another step will occur on the other side of that boundary.
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| 33 | In summary the "production threshold" range and its equivalent in energy
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| 34 | are not utilised as a "tracking cut". A particle is not abandoned by
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| 35 | Geant4 below a certain range/energy unless the user registers a process
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| 36 | to do this by him/her-self.
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| 37 | </p></td></tr></tbody></table></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ch10s04.html"><img src="AllResources/IconsGIF/prev.gif" alt="Prev"></a> </td><td width="20%" align="center"><a accesskey="u" href="ch10.html"><img src="AllResources/IconsGIF/up.gif" alt="Up"></a></td><td width="40%" align="right"> <a accesskey="n" href="ch10s06.html"><img src="AllResources/IconsGIF/next.gif" alt="Next"></a></td></tr><tr><td width="40%" align="left" valign="top">FAQ.4.
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| 38 | Tracks and steps
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| 39 | </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"> FAQ.6.
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| 40 | Visualization
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| 41 | </td></tr></table></div></body></html>
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