- Author
- danie.nosp@m.la.r.nosp@m.ebuzz.nosp@m.i@pv.nosp@m..infn.nosp@m..it
-
nveld.nosp@m.ik@n.nosp@m.ikhef.nosp@m..nl
Class methods and properties
The method MDTSensitiveDetector::ProcessHits is executed by the G4 kernel each time a charged particle (or a geantino) crosses one of the MDT Sensitive Gas volumes.
Once a G4Step is perfomed by the particle in the sensitive volume (both when the particle leaves the tube or stops in it), Pre and PostStepPositions are tranformed into local coordinates (chamber reference system, with Z along the tube direction and XY tranversal plane) and used to calculate the local direction of the track.
Two cases are given: 1) the particle over-passed the wire: here the drift radius (the impact parameter) is computed as the local direction distance from the wire;
2) the step doesn't allow the particle to over-pass the wire: here the shortest distance to the wire, which is one of the two end-points, is calculated for each step which occurs inside the sensitive volumes and only the closer one is kept; this case includes also the hard scattering case inside the sensitive volume.
Navigating with the touchableHistory method GetHistoryDepth() through the hierarchy of the volumes crossed by the particles, the MDTSensitiveDetector determinates the correct set of geometry parameters to be folded in the Simulation Identifier associated to each hit. The MDT SimIDs are 32-bit unsigned integers, built using the MuonSimEvent/MdtHitIdHelper class which inherits from the MuonHitIdHelper base class.
We describe in the following, how each field of the identifier is retrieved.
1) stationName, stationEta, stationPhi: when a volume is found in the hierarchy, whose name contains the substring "station", the stationName is extracted from the volume's name; stationPhi and stationEta are calculated starting from the volume copy number, assigned by MuonGeoModel.
2) multilayer: when a volume is found in the hierarchy, whose name contains the substring "component", the multilayer is set to 1 or to 2, according to the component number (multilayer=1 if the component is 1, 5 or 8; multilayer=2 if the component is 3, 7, 8, 10, 11 or 14).
3) tubeLayer and tube: when a volume is found in the hierarchy, whose name contains the substring "Drift", tubeLayer and tube are calculated starting from the Drift volume copy number.
notes:
1) this implementation of the MDT Sensitive Detectors can handle different situations: hard scattering of the muon on the sensitive volume (its direction changes), soft secondary particles completely included in the sensitive volume, muon hits masked by secondaries, like delta rays.
2) for each hit, the time of flight (the G4 globalTime), is recorded and associated to the hit.
3) more than none MDT hit can occur in the same tube. The hit selection is done at the level of the digitization procedure.
4) the MDTHit object contains: the SimID, the drift radius and the globalTime.
Definition at line 84 of file MDTSensitiveDetector.h.
1.8.18