January 25, 2008 Software

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  1. Review minutes from December 7, 2007 Software meeting
  2. bggen hadronic generator(s) (Eugene)
  3. FDC reconstruction [1](Simon)
  4. Momentum and angle resolution estimates (PDF)(Mark)
  5. Photon (conversion) and reconstruction (efficiency) obtained for 1 GeV photons thrown from the target uniformly in azimuth and up to 20 degrees in polar angle. Conversion probability is estimated by registering shower particles (MCTruth) that do not originate from the vertex. Efficiency: single photon reconstruction requires photon energy within 3*sigma_E of generated energy, where segma_E is detector specific energy resolution, and polar angle within 5% of generated angle. (Mihajlo)
  6. Action Items



The meeting will be at 2:00pm in Cebaf Center F326-327.


To connect by telephone: 1.) dial:

800-377-8846 : US
888-276-7715 : Canada
302-709-8424 : International

2.) enter participant code: 39527048# (remember the "#")

Video Conferencing

We will attempt an ESNet connection for this meeting using the following number:


We have a reasonable expectation that this will work.


Attendees: David L.(chair), Simon T., Eugene C., Elton S., Mark I., Elke A.

Remote: Mihajlo K.

Hadronic Generators

Eugene presented the bggen hadronic generator. This combines the lowengen and pythiagen generators he had developed earlier and presented at previous meetings. The new generator allows one to specify incident photon energies from the pion threshold (~150MeV) up to GlueX energies of 9GeV. This tool will be useful in understanding the general hadronic physics background in the detector. It will also be very useful for studying the L1 trigger with simulation.

The bggen program is currently in the subversion repository (src/programs/Simulation/bggen) and ready for use.

FDC Reconstruction

Simon gave an update on the continuing work on the FDC reconstruction. He showed a plot indicating a relatively minor change in the momentum resolution due to the change of the FDC cathode strip angle from 45o to 75o.

Also shown was how the track candidate resolution improved when including a 3rd package in the determination of the track parameters from the candidate.

Finally, Simon showed evidence of a bug introduced with the new V4 geometry that resulted in drop in single hit efficiency by about 40%. He had already located and fixed the bug and so was able to show angular and momentum resolutions after the fix.

Momentum Angle Resolution Measurements

Mark gave an update on work he is doing to try and calculate the momentum and angular resolutions we should expect using simple formulas and knowledge of the amount of material and number of measurments in our tracking chambers. He currently gets around 15%-20% agreement with calculations from momres and earlier M.C. studies of 90o tracks. The goal here is to try and extend the method into the FDC region and use it to estimate the dependance of reconstructed quantities on the amount of material in the chambers. Work is continuing in this area.

Photon Reconstruction Efficiency

Mihajlo presented results from a simulation study he did using 3 different geometries. In the study, he generated photons in the forward direction and tried reconstructing them in the FCAL and BCAL. He plotted the efficiency(descibed in the agneda above) of the reconstructed photons as a function of angle for all 3 geometries. A marked improvement was made due mainly to the reduced material in the FDC frames. The "gap" was now significantly narrower.

Action items

No specific action items were discussed.