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2 | <!-- --> |
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3 | <!-- [History] --> |
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4 | <!-- 1st version created: Katsuya Amako, Dec-2006 --> |
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5 | <!-- --> |
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6 | <!-- ******************************************************** --> |
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7 | |
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8 | |
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9 | <!-- ********************* QandA Section ******************** --> |
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10 | <section id="qanda.PhysicsCuts"> |
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11 | <title> |
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12 | Physics and cuts |
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13 | </title> |
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14 | |
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15 | <qandaset defaultlabel="qanda"> |
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16 | |
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17 | |
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18 | <!-- ******* QandA Entry ******** --> |
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19 | <qandaentry id="qanda.PhysicsCuts.HowProdCuts"> |
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20 | |
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21 | <question><para> |
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22 | How do production cuts (in range) work in Geant4 ? Are they also used |
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23 | in tracking ? If a particle has an energy lower than the converted cut |
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24 | in energy for the given material and the distance to the next boundary |
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25 | is smaller than the cut in range, is the particle killed ? |
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26 | </para></question> |
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27 | |
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28 | <answer><para> |
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29 | Geant4 does <emphasis role="bold">NOT</emphasis> have a "tracking cut". |
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30 | The toolkit's default behaviour is to track particles down to zero range |
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31 | (i.e. zero energy). Of course, it is possible for the user to create and |
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32 | register a process that kills particles below a certain energy or range; |
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33 | this is however <emphasis role="bold">NOT</emphasis> provided by default |
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34 | in Geant4. So there's <emphasis role="bold">NO</emphasis> "tracking cut". |
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35 | For example, suppose a particle that is nearing zero energy will at some |
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36 | point be proposed by its Ionisation process to undergo one final step, |
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37 | from its current energy down to zero energy. This is still only a |
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38 | proposal. If during this step the particle crosses a boundary, then the |
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39 | transportation will limit the step at a length smaller than the |
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40 | Ionisation -- so the particle will still see and cross the relevant |
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41 | boundary, and another step will occur on the other side of that boundary. |
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42 | In summary the "production threshold" range and its equivalent in energy |
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43 | are not utilised as a "tracking cut". A particle is not abandoned by |
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44 | Geant4 below a certain range/energy unless the user registers a process |
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45 | to do this by him/her-self. |
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46 | </para></answer> |
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47 | |
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48 | </qandaentry> |
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49 | |
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50 | |
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51 | </qandaset> |
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52 | </section> |
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