| 1 | This is an example illustrating the use of the error propagation utility. |
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| 3 | A G4ErrorFreeTrajState is created to simulate a muon track of 20 GeV along the X axis. Then the track is propagated until the target is reached. |
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| 5 | The geometry is a simplified typical HEP detector: |
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| 6 | An air beamline ( BEAM ) |
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| 7 | An air central detector ( CDET ) |
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| 8 | A copper calorimeter, divided in four ( ECAL ) |
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| 9 | An aluminium calorimeter, divided in ten ( HCAL ) |
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| 10 | An air muon detector ( MUON ) |
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| 11 | |
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| 12 | It is inmersed in a magnetic field along the Z axis with default value -1 kilogauss. This value can be changed with the command "/exerror/setField. |
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| 15 | The type of target can be chosen with the enviromental variable G4ERROR_TARGET: |
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| 17 | PLANE_SURFACE : use a G4ErrorPlaneSurfaceTarget perpendicular to X at (2241. mm, 0, 0) |
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| 18 | CYL_SURFACE : use a G4ErrorCylSurfaceTarget parallel to Z of radius 2220 mm |
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| 19 | VOLUME : use a G4ErrorGeomVolumeTarget with volume name "MUON" |
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| 20 | TRKLEN : use a G4ErrorTrackLengthTarget with track length 2230 mm |
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| 23 | The user may also choose if the propagation is done forwards (the natural way, loosing energy) or backwards (in opposite direction, gaining energy), with the enviromental variable G4ERROR_MODE: |
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| 24 | |
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| 25 | FORWARDS : propagate in the forward direction |
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| 26 | BACKWARDS : propagate in the backward direction |
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| 29 | There are also two modes of propagation, that can be chosen with the enviromental variable G4ERROR_PROP |
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| 31 | UNTIL_TARGET : propagate until target, all steps in one go |
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| 32 | STEP_BY_STEP propagate until target, returning control to the user at each step |
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