August 27, 2014 Calibration

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GlueX Calibration Meeting
Wednesday, August 27, 2014
11:00 am, EDT
JLab: CEBAF Center, F326

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  1. Announcements
  2. Commissioning Planning
  3. Fall 2014 Commissioning Simulations
    • Status Update
      • Commissioning target geometry in branch hdds-commissioning

Commissioning target.png Commissioning target closeup.png

    • Number of Events & Final States
    • EM Background Simulations (Sean)
    • EM Background Simulations (Simon)
      • Mockup of Level 1 trigger:
        • Version A: (Ebcal + 4.0 Efcal)>=2.0 && Ebcal>0.200 && Efcal>0.030
        • Version B: (Ebcal + 4.0 Efcal)>=2.0 && Ebcal>0.030 && Efcal>0.030 && N(start counter hits)>0
        • Version C: Efcal>=0.250
        • Version D: Efcal>=0.250 && N(TOF hits)>0
      • Coherent bremsstrahlung generator: 10 GeV electron beam, 5 mm collimator, Emin=1.2 MeV.
Events Trigger Events with segments
97172 169 70 44 44 122 67 29 29
Fraction: 0.0017 0.0007 0.0005 0.0005 0.0013 0.0007 0.0003 0.0003
  1. Action Items
  2. AOT

Action Items

  • Update desired event counts (all)
  • Tag new sim-recon version (Mark I.)
  • Update geometry for commissioning running (Simon)
  • Obtain new constants for EM background simulation & magnetic field (Sean)
  • Update expected photoproduction event rate calculations
  • Decide number of events & conditions to simulate
  • Run simulations
  • What is the lowest solenoid current that we can run at? How will a low solenoid current affect FDC alignment?
  • Study FCAL & BCAL trigger thresholds


Attending: Sean (CMU); Naomi, Curtis (CMU); Matt S., John Z. (IU); Simon, Lubomir, Beni, Mark I., Mark D., Eugene (JLab); Zisis, Tegan (Regina); Justin (MIT)


Curtis mentioned that in the latest meetings with the accelerator group, it sounds like there will be the possibility of taking additional data on evenings and weekends in November and December, beyond the 3 weeks we have been planning for. Therefore, we should be planning to make as many calibrations as possible with the available data.


  • Naomi presented an updated commissioning plan, which had two main parts. In early running, old HV supplies would be attached to the inner straws to measure the currents induced by the photon beam. After that, a healthy sample of tracks taken with the magnetic field off are needed.
  • Beni suggested to look at what would happen if targets at different positions and with different thicknesses were used.
  • Simon has been running his alignment code with the currently collected cosmic data, which is giving generally reasonable results though there are some outliers. He plans to update his stimaes of how much data is needed. His current alignment plugin needs some small changes to work with straight tracks from the target instead of cosmics.
  • Generally, an estimate of how much raw mode data is needed would be useful.


See simulations below.


  • The pi0 energy calibration code originally developed by Claire Tarbert is in several pieces. Matt is working with John Z. to collect this code and get it working in the DANA framework. This work has been delayed by several problems installing the GlueX offline software.
  • The plan is to start with pi0's being produced with the particle gun and work up to analyzing and balancing the gains using EVIO files.
  • An undergrad student is looking at omega photoproduction, with the decay omega -> gamma pi0.
  • The first pi0 data will be used to refine the PMT gain balancing. Further gain balancing can be done in software.
  • In principle, the first pass at timing calibrations can be done with data from the the LED monitoring system. This data is currently being analyzed.


  • Zisis presented and reviewed the plans for BCAL calibration that were developed earlier this year. These plans are being updated based on the experience with cosmic data and simulations. The reconstruction software is being updated as well.
  • Mark D. reported that the current checks and calibrations are data limited - they plan to take as much cosmic data as they can before the beam.
  • Plans for pi0 and charged hadron energy calibration were developed a few years ago and need to be revisited.
  • Sean mentioned that it would be useful to know how the current calibrations will affect efficiencies during the fall running.
  • Beam data taken with and without magnetic field will be useful, the latter especially to determine the response of curving charged particles.
  • There have been problems installing the latest offline software at Regina as well.
  • Zisis requested 30% of the GlueX simulation needs on the Canadian Westgrid platform, and this request was well received.


  • Sasha O. is working on calibrations with the data currently in hand. Progress is being made though he is running into some trouble with events that have a lot of hits. Plans are to take more data.
  • They request to have some running with a thick target to determine the hit rates expected for the hydrogen target.

Start Counter

  • It is being constructed and hoped to show up at JLab next week. Fingers are being crossed.


  • Simon has been working on a branch of HDDS to update the geometry for the fall run. He has added the geometry for the commissioning target and updated the start counter geometry while he was at it. Some work remains to be done with the upstream geometry, where a plastic cap on the beampipe will be added. During the fall run, there will also be the option of placing the SciFi beam profiler in the beam, which would act as a third target.
  • Simon is also going to implement a system in hdgeant that will sample a histogram of the density along the beam's path to decide where to place photoproduction events. This is needed to handle the multiple targets along with the several interaction lengths of air that the beam will pass through.
  • Simon then reported on some trigger studies he has started. He generated events using the bremsstrahlung beam generator under fall running conditions and looked to see how many photons passed various trigger criteria. The results are in the table above. The results have low statistics, but note that the collimator acceptance is included in the beam simulation.
    • Justin pointed out that the default trigger thresholds are set for accepting high photon energy events and may not be efficient for triggering on lower energy events. Another problem is that for the FDC and TOF they need charged particles which tend to leave minimum ionizing signals in the FCAL.
  • Sean presented a first look at some simulations at various magnetic field settings, in an attempt to determine which magnetic fields to run simulations at. He generated bggen events with EM background included with the following magnetic field settings: None, 50A, 100A, 200A, 300A, 1200A, and looked at the relative rates in the detectors.
    • Generally, the inner CDC and TOF rates were insensitive to magnetic field. Some variation was seen in the FCAL and FDC, but these was little difference between no magnetic field and the 300A magnetic field. At 300A, the rates at which different FDC packages were populated were visually different compared to no magnetic field, but a numerical analysis is needed.
    • He will develop these studies and calculate overall rates.
    • He will also investigate EM backgrounds for physics running at various field currents (tentatively None, 750A, 1200A, 1500A).

  • Sean proposed simulating 200M events with E(gamma) > 1 GeV, each with the magnet on (1200A) and off, corresponding to 1kHz event rate for a week @ 50% efficiency. There was little discussion about whether this amount would be enough or not, so we'll use it for a start. Eugene said that we should extend these studies down to threshold.