GlueX Offline Meeting, May 18, 2011

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GlueX Offline Software Meeting
Wednesday, May 18, 2011
1:30 pm EDT
JLab: CEBAF Center A110


  1. Announcements
  2. Review of minutes from the last meeting: all
  3. Action Item Review: all
  4. Review of recent repository activity: all

Communication Information


To connect by telephone:

  1. dial:
  2. enter access code followed by the # sign: 3421244#

Video Conferencing


Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2011-2Q on the JLab CUE. This directory is accessible from the web at . You have to be a member of the "halld" Unix group to do this.


Present: Mark Ito (chair), David Lawrence, Paul Mattione, Kei Moriya, Nathan Sparks, Simon Taylor, Beni Zihlmann

Track Reconstruction Problems in Cascade Events

  • David: some tracks exhibit trajectories that curl tighter as they travel downstream.
  • We still need work on track candidate finding.
  • David has worked on a new hit selector that may help.
  • Mark speculated that curling tracks may not be one of the things we can do well initially.

Documentation on Getting Started

  • Beni did a major rework of the Offline Software wiki page. Many favorable comments were offered.
  • Paul has been working from the wiki documentation and finds it "pretty straightforward", to the surprise of many.

"b1pi" Problem

  • David pointed Paul to the howto on generating and reconstructing b1pi events. They discovered in the process that the reconstruction efficiency is not what it used to be: down from about 50% to about 5%.
  • This needs to get attention.

Bad Hits and the Kalman Filter

Simon got some questions on the sensitivity of the Kalman filter to bad hits on the track.

  • Bad hits can throw the Kalman filter off. The ALT1 is more robust against inclusion of anomalous hits.
  • Hits at the outer parts of the detector cause a particular problem since information about the track is refined from the outside in. A bad hit on the outside has more influence on the trajectory at the time it is added and can cause the fit to fail.
  • There are various options to reduce this sensitivity:
    • "annealing" algorithm
    • rejection of poor hits as they are considered for addition to the fit

Definition of Primary Particles

  • We will get a talk from Beni on this subject. It became an issue when he introduced changes to do studies correlating hits with generated particles.
  • Some changes have been made recently. They should help Matt Shepherd resolve his problem he was having with identifying primary photons.

IT Review

Mark reminded us that there will be a review of "Information Technology at JLab in the 12 GeV Era" tomorrow. There is a webpage for the review which contains a link to the charge to the committee. Mark will present the view from Hall D.

David asked how any comments/findings/recommendations of the review will impact our plans. Mark said that that remains to be seen, but we should probably take any feedback from the committee as an opportunity to look hard at what we are doing.

Figure Repository

Kei wondered where we are with that. Zisis Papandreou announced a plan at the Collaboration meeting. We should track progress.

New Action Items

  1. Investigate problem reconstructing "b1pi" events.
  2. Give talk on the definition of primary and secondary particles in HDGeant. -> Beni