April 22, 2015 Calibration

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GlueX Calibration Meeting
Wednesday, April 22, 2015
11:00 am, EDT
JLab: CEBAF Center, F326

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Agenda

  1. Announcements
  2. Collaboration Meeting
  3. Subdetector Reports
    • Calibration Progress
    • Resolutions / Efficiencies
  4. Simulations
  5. Spring Calibration Plans
  6. Normalization

Minutes

Attending: Sean, Simon, Adesh, Lubomir, Justin, Paul, Eugene, Will M., Beni, Alex, Eric, Elton, Mike S., Luke, Kei (JLab); Curtis (CMU)

FCAL

Adesh reported that not much progressed had been made. The major current puzzle is that when looking at showers due to electrons, although the overall cluster energy has a resolution ~10%, the individual block energies have resolutions of ~30%. They have made progress in determining the efficiencies of showers due to electrons, but are held up with this problem. Will M. has agreed to look at the pi0 minimization procedure, based on his experience with using it for the BCAL.

BCAL

Elton reported that the efficiencies depend on many variables, including how different types of hits are treated and which layer is being looked at. These issues are a major current focus. Another recent major effort was developing better running conditions. These include variable fan speeds on the crates (h/t Mark Dalton), running at a lower temperature (10 degrees down from 18 degrees), and a higher over-voltage (1.4V versus 1.0V). Will M. is looking for eta -> gamma gamma decays, since none have been seen yet so far in the fall data. He is looking at the data and simulations to determine the prospects for measuring this. It was also suggested that the characterize the pi0 reconstruction performance over a wider energy range.

CDC

Naomi has continued looking into the gas mix, and has developed a plugin for monitoring the drift times. David L. and Sean have been looking into running it as an online monitoring process. Mike S. has been looking into using the Millipede program as a complementary alignment strategy. This is a standard program used by many other experiments for alignment, by building and inverting large sparse matrices. For comparison, CMS did the alignment of their silicon tracker muon system, which had ~4000 parameters, using 4M cosmic rays. Over a weekend, with a good DAQ running (rate ~1.8 kHz, live time ~99 %), we recorded ~100M triggers, O(1-5%) of which are cosmic rays.

More data with the HV power supply filters are needed to characterize the FDC, since the noise levels are now back down to normal. Beni said that he had taken good cosmic data lately. Eugene suggested running this procedure on simulated data to make sure it works.

FDC

Lubomir has given a full set of alignments to Simon, who is checking them out today. These are only first order corrections - there is some residual sinusoidal dependence (probably due to signal propagation) that remains to be understood. The reconstruction is still only using cathodes, but now the wire TDC times are better understood, so that they can be integrated.

TOF

Beni recently made per-channel time offset corrections, and Simon checked them into the CCDB. These are the first offsets that have been added for the TOF. See Tuesday's TOF meeting for the details of the calibration, but note that it was only done for double-ended paddles of normal width (i.e. not the single-ended or narrow paddles around the beam line), and greatly enabled by knowing the correct CAEN TDC time binning.

Simon finds the combined TOF/ST time resolution to have decreased from ~1ns to 700 ps. Beni also obtained effective velocity values that Simon is looking into. Sean is looking at the track/TOF matching in some detail to make sure that these new constants line up with other detectors. Energy scale and updated time walk corrections are also on the list.

Start Counter

  1. Simulations
  2. Spring Calibration Plans
  3. Normalization
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