April 9, 2014 Calibration

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GlueX Calibration Meeting
Wednesday, March 25, 2014
11:00 am, EDT
JLab: CEBAF Center, F326

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  1. Announcements
  2. Collaboration Meeting May 12-14
  3. Status Update
  4. Tracking
  5. Calorimetry
  6. Other systems
  7. Simulations and Calibrations


Attending: Sean, Amiran (NU); Curtis, Naomi (CMU); Simon, Beni, Michael S. (JLab); Zisis (Regina)

  1. Collaboration Meeting May 12-14
    • At the May CM, Sean will give an overview talk and Simon will talk about his work with drift chamber alignment. Sean will go around to the other detector groups to see what other talks might be needed.
  2. Status Update
    • Sean went over some new wiki pages, which included the definitions of current and proposed tables, defined variations, and comments that were kept in the text calibration files but that did not make it into the CCDB. Tables for all subdetectors have been defined or proposed. Relevant procedures will also be documented. As we are in the development stage for most codes, for now the only two are (1) document any changes you make, and (2) let the relevant people know about them.
    • Beni mentioned that he had a table added to the online CCDB to store the sparsification thresholds for the FDC. This shouldn't be needed for offline analysis of physics data, but may be needed for commissioning/calibration, so its existence should be kept in mind. The issues of synchronization between the online and offline CCDBs should be addressed in the future.
  3. Tracking
    • Simon presented updated results on drift chamber alignment
      • For the CDC, he now uses cosmic rays generated with the CRY generator (adapted for the GlueX framework by Michael Staib). With 330,000 cosmics using the BCAL for a trigger, he finds generally good determinations of the wire alignment parameters in x and y. The agreement for the first ring is within ~100 microns for x, and ~200 microns for y, and is better for axial straws than stereo, and better for closer-in layers.
      • For the FDC, he reminded us of his good determinations of the wire plane parameters, and showed a determination of the alignment parameters for the cathode planes. The rotation (phi) parameters were well-determined, but the determination shift parameters did not converge well.
      • Curtis asked about the expected cosmic rate for the CDC, and Zisis said it was 80 m^-2 s^-1 sr^-1.
      • The comissioning target is a small plastic disk, and can be moved in z to some extent. Simon is investigating the effects of different target locations.
    • Naomi reported on some studies on using time-to-distance tables using different straw diameters. Previous studies at CMU had shown that some of the straws were deformed, with apparent radii up to 10mm, compared to a nominal 8mm. Using time-to-distance lookup tables generated for radii of 8,9,10 mm, differences in calculated drift distance approached ~1 sigma of resolution as distance approached the maximum straw radius. This should be studied more with actual cosmic data: it is a measurable, if small affect, and is guessed to affect ~1% of hits. Curtis mentioned that truncating the drift times and throwing out these late hits is a possible solution, given the potential of bringing in larger backgrounds by extending the drift time window.
  4. Calorimetry
    • Zisis mentioned that they are preparing to take cosmics data with the BCAL in the coming weeks.
  5. Simulations and Calibrations
    • Sean found some bugs in the MC sample he had generated, and has not been able to generate any more due to the ongoing data challenge. He showed the parameters of the updated calculation he will perform once the data challenge is finished. Simon is working on developing the geometry code for the comissioning target, and it is hoped to be able to use this.