Detailed Description

Class methods and properties

The method sTgcSensitiveDetector::ProcessHits is executed by the G4 kernel each time a particle crosses one of the sTgc gas gaps. Navigating with the touchableHistory method GetHistoryDepth() through the hierarchy of volumes crossed by the particle, the Sensitive Detector determines the correct set of Simulation Identifiers to associate to each hit. The sTgc SimIDs are 32-bit unsigned integers, built using the MuonSimEvent/sTgcHitIdHelper class which inherits from the MuonHitIdHelper base class.

We describe here how each field of the identifier is determined.

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. stationEta and stationPhi values are calculated starting from the volume's copy number.

2) doubletR: when a volume is found in the hierarchy whose name contains the substring "sTgccomponent", its copy number is used to calulate the doubletR of the hit.

3) gasGap: the substring "layer" is searched through the names of the volumes in the hierarchy. When a the volume is found, its copy number is used, together with the sign of the copy number of the "sTgccomponent" to decide what is the correct gasGap value.

4) doubletPhi: when the volume with the substring "gas volume" in its name is found, its copy number is enough to determine the doubletPhi of the hit if the hit is registered in a standard chamber. For special chambers (i.e. chambers with only one gas gap per layer readout by two strip panels per direction, or chambers in the ribs) some a special attribution is done using also the stationName.

5) doubletZ: "gazGap" is the required substring in the volume's name. doubletZ attribution is fairly complicated. For standard chambers it just uses the sign of the copy number of the "sTgccomponent", but severa arrangements (based on the stationName and the technology name) are needed for special chambers.

6) the doubletPhi calculated as described above needs one further correction for some chambers to take into account chamber rotation before placement in the spectrometer. This is done just before creating the hit.

notes:

1) presently, chamber efficiency is assumed to be 100% at the level of the Sensitive Detector, i.e. two hits (one in eta and one in phi) are created each time the sensitive detector is created.

2) the hits created as described above contain information about their local position in the gas gap and the simulation identifier of the strip panel

3) the strip number is not assigned by the sensitive detector, and must be calculated by the digitization algorithm.

4) points 2 and 3 are due to the necessity of not introducing any dependency on the geometry description in the Sensitive Detector.

5) the present version of the Sensitive Detector produces hits which are different depending on whether hand coded G4 geometry or GeoModel is used for the geometrical description of the setup. When hand coded geometry is used, both GeoModel and the old MuonDetDescr can be used for digitization (using a proper tag of sTgc_Digitization), while if GeoModel is used in the simulation, it must be used also in the digitization.

6) for each hit, the time of flight (the G4 globalTime), is recorded and associated to the hit.

7) the sTgcHit object contains: the SimID, the globalTime, the hit local position and the track barcode.

The documentation for this class was generated from the following file:

sTgcSensitiveDetector.h