IRF Format and IRF Identifers for the BFEM geometry

Monte Carlo    TKR    CAL    ACD    XGT

ROOTWriter will accept IRF files as input and then convert that data into a Root file.  The BFEM Geant4 simulation's output can be converted into IRF format.  This includes assigning the appropriate ID numbers to each of the detectors. The first attempt at converting G4 data into IRF format used the identifiers that were defined using the testbeam 1999 format.  The identifier scheme is described in Section 2.4 of the document "Current Status of Geant4 Development and Validation".

The Geant 4 BFEM team has updated the IRF, incorporating more detailed Monte Carlo data.  The data from a Geant 4 simulation is converted into IRF using a PERL. A complete description of the IRF converter and description of the format is available.

Work has been completed to update the geometry information available to ROOTWriter to reflect the BFEM configuration.  This has caused the IRF identifiers assigned to the various detectors to be modified.  This document will describe the IRF identifiers as they now exist for the BFEM.  All code related to converting G4 data into IRF format should be updated to reflect the new identifier scheme.

NOTE:  The IRF expects all energies for MonteCarlo, ACD, and CAL to be in GeV.  The TKR reports charge in the strips as fC (fempto-Coulombs).

MC (Monte Carlo)

For a detailed description of the MC record in the IRF file, please see this page.

TKR (Tracker)

For a nice detailed description of the TKR IRF format - please see this IRF description.

Note that the TKR data is output to an IRF such that there is only one line per TKR id per event.  For example, for 2 hit strips on one TKR layer:
406 2.32075471698113 2 143 2.32075471698113 0 144 2.32075471698113 0 |
where:
406 is the TKR layer IRF id
2.32075471698113 is the max charge seen on this layer in fC
2 is the number of hits on this TKR layer
143 is the Strip Id for the first hit
2.32075471698113 is the charge deposited in this strip in fC
0 denotes that this hit is not a noise hit
144 is the Strip Id for the second hit on this TKR layer
2.32075471698113 is the charge deposited in fC
0 denotes that the second hit was also not a noise hit.

The numbering in the TKR is the same as described in the document "Current Status of Geant4 Development and Validation":

Each tracker layer gets one ID, mapped by:

irfID = 404 + ID where ID are the layer numbers 0...25 (the BFEM has 26 layers - unlike the BTEM which had 32).

We will reserve [404, 435] for the TKR IRF ids, to allow for either a BTEM or BFEM configuration.  Note that for the BFEM only [404, 429] would be valid, where 404 corresponds to the back-most (closest to the CAL) layer = 0.

CAL (Calorimeter)

An IRF record for the CAL looks like:
7 0.00866083 0.0100125 0.0186733
where:
7 is the IRF id
0.00866083 is in GeV and is the amount of energy seen on the left (negative) end of the log.
0.0100125 is in GeV and is the amount of energy seen on the right (positive) end of the log.
0.0186733 is in GeV and is the combined response of both the negative and positive ends of the CAL log.

The CAL identifiers are unchanged.  The description available in the document "Current Status of Geant4 Development and Validation" should be accurate:

"They [the CAL IRF ids] are arranged from 2 to 397 with a spacing of 5 which gives us a total of 80 logs.  The numbering is done in the following way:"

irfLogID = 2 + 5(10(7-Layer) + (LogID))         y-layer (logs are oriented along the y direction)

irfLogID = 2 + 5(10(7-Layer) + (9-LogID))     x-layer (logs are oriented along the x direction)

NOTE:  Be sure to check the meaning of LogID in this instance!!!

The CAL numbering scheme in the IRF is as follows:
1. Layers are numbered 1 to 8 from bottom to top, i.e. layer 1 has a more negative Z than layer 8.
2. Within a layer, the log number increases with increasing X or decreases with increasing Y. The log number runs from 1 to 12.
3. Tower numbering runs 0 to 15, but I don't know whether it counts faster in X or Y.

ACD (Anti Coincidence Detectors)

An IRF record for the ACD looks like:
437 0.0539827
where:
437 is the IRF id for the ACD tile
0.0539827 is in GeV and is the amount of energy deposited in the tile.

The IRF ids currently run from [437, 449].  Note the BFEM ACD tile numbering scheme as described by Steve Ritz is shown in this diagram.

XGT (eXternal Gamma Target)

The IRF records for an XGT will be identical in form to the ACD.

The four XGTs have IRF ids:  [450, 453]