E852 Documentation: The MPS Efficiency Measuring Program

Introduction

The MPS Efficiency Measuring program, 'mpsEfficiency' estimates the MPS tracking chamber efficiencies.

To estimate efficiencies of beam chambers, please use the mpsBeamPwcMon program.

See the output of 'mpsEfficiency -h' (usage) for information on switches accepted by the program but not described in this document.

In case of inconsistencies between this document and the program's usage, the program's usage should be assumed to be more correct.

Using the program

The following tasks can be done using the mpsEfficiency program:

print chamber efficiencies stored in the Map for a given run number.
calculate the chamber efficiencies using a data file.
- using extrapolated beam tracks (-b) switch,
- using reconstructed tracks (default),
- using monteCarlo tracks (-p) switch.
save the calculated efficiencies into the Map for a given run number.

Print efficiencies

To print chamber efficiencies for a given run number, use the command:

	> mpsEfficiency -rxxx

for example,

	> mpsEfficiency -r8989

After loading the parameters database, the program will produce the following output:

----------------------------------------------------------------------
 Chamber    hits: found/expected  efficiency: new/  file/   Map/  save
----------------------------------------------------------------------
   AX111              0/       0             1.00   1.00   1.00   1.00
     ...
     FX2              0/       0             1.00   1.00   0.77   1.00
     FX3              0/       0             1.00   1.00   0.74   1.00
     FY1              0/       0             1.00   1.00   0.78   1.00
     FU1              0/       0             1.00   1.00   0.79   1.00
     FV1              0/       0             1.00   1.00   0.83   1.00
     FY2              0/       0             1.00   1.00   0.93   1.00
    TPX3              0/       0             1.00   1.00   1.00   1.00
   TDX4A              0/       0             1.00   1.00   1.00   1.00
   TDX4B              0/       0             1.00   1.00   1.00   1.00
----------------------------------------------------------------------

The values stored in the Map are shown in the efficiency/Map column.

Calculate efficiencies

To calculate chamber efficiencies for a given data set, using reconstructed tracks, use the command:
```
	> mpsEfficiency -rxxx inputFiles...
```
for example,
```
	> mpsEfficiency -r8989 input.dat
```
To calculate chamber efficiencies for a given data set, using extrapolated beam, use the command:
```
	> mpsEfficiency -b -rxxx inputFiles...
```
for example,
```
	> mpsEfficiency -b -r8989 input.dat
```
The input file should have the following data groups: GROUP_TRACKS, GROUP_PATREC and the drift chamber and TPX hits groups.

The calculated efficiencies are saved in the mpsEfficiency.db file in the current directory. If necessary this file can be edited using a text editor to assign arbitrary efficiency values. Values saved into this file can then be loaded into the Map using the mpsEfficiency program.

After loading the parameters database, the program will produce the following output:

----------------------------------------------------------------------
 Chamber    hits: found/expected  efficiency: new/  file/   Map/  save
----------------------------------------------------------------------
    TPX1            200/     200             1.00   1.00   1.00   1.00
     BX1            186/     200             0.93   1.00   0.96   0.93
     BX2            196/     200             0.98   1.00   0.95   0.98
     BX3            186/     200             0.93   1.00   0.91   0.93
     BY1            182/     200             0.91   1.00   0.93   0.91
     BU1            174/     200             0.87   1.00   0.81   0.87
     ...
----------------------------------------------------------------------

The first column gives the chamber name, the second and third the hit count, the efficiency columns are:

new - the newly calculated efficiencies.
file - values saved in the mpsEfficiency.db file.
Map - values stored in the Map.
save - values that will be written into the Map if the program was invoked with the -w switch.

Save efficencies

To store efficiencies saved in the mpsEfficiency.db file, use the command:

	> mpsEfficiency -rXXX -wYYY

where YYY is the run number used to store the data. Normally XXX and YYY are equal. Example:

	> mpsEfficiency -r8989 -w8989

Caveats, bugs and spiders

As of today 18-Dec-1994 the program has the following bugs:

The efficiencies of the first and the last chambers are always 100%. This is because of how the beginning and the end of the track are defined: a track begins from the first chamber it hits and ends at the last chamber it hits. With this definition the first and the last chambers are 100% efficient.
The above problem also causes overestimation of efficiencies for the chambers "near" the first and the last chamber. However this effect does not seem to propagate further than 1-2 chambers.
The program uses reconstructed tracks to measure efficiencies. This will cause their overestimation.
Beam chamber efficiencies are not measured.
TDX4 efficiencies are not measured.

Theory of operation

On extrapolated beam and montecarlo data (-b or -p switches)

The program swims the tracks through the detectors and builds a "fake" pattern recognition group. Hits are placed into this pattern recognition group if they fall within a given wire range from the hit. This range can be changed using the -Wnwires command line argument.

Once constructed this fake pattern recognition group is used as described in the next section.

On physics data

The program uses the pattern recognition data (GROUP_PATREC_TRK) and requires that all the planes between the first plane and the last plane have hits. If hits are missing in the middle planes, they count as inefficiencies.

The method has a drawback in that it does not allow for calculations of efficiencies for the first and last planes on the track.

//CO 18 Dec 1994