Π polarizability Software Meeting Apr 21, 2022

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Meeting Time And Location

12:30 EST (JLab time) Thursdays Weekly Meeting

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Agenda

  1. Previous Meeting
  2. Pending Pull Requests and Reviews (CPP branch)
  3. Geometry and Simulation
  4. FMWPC Library
    • DFMWPCHit - Calibrated hits
    • DFMWPCCluster
    • DFMWPCMatchedTrack
    • DCTOFDigitHit, DCTOFHit, DCTOFPoint
  5. PID:
    • e+e- PID
      • input features
        • FCAL Shower Energy/Kinfit Momentum
        • FCAL E9/E25 Shower Ratio
        • FCAL DOCA
    • πμ classification
  6. Event viewer
  7. Monitoring
  8. AOT

Monitoring ideas

The following suggested by Rory in an e-mail on Mar. 24, 2022

  1. invariant mass of the 2 pions
  2. t-distribution
  3. The azimuthal distribution of the pi+pi- momentum vector relative to the polarization direction (usually the x or y axis)
  4. The azimuthal distribution of the pi+ in the helicity frame. Here’s where my understanding drops off. See the diagram below from Alex. I think we want to plot Psi = (phi - Phi), with phi and Phi shown in the figure below. phi seems easy, it’s the angle between pi+pi- production plane, and the plane formed by the incident nucleus and recoiling nucleus. However, what I’m not clear on from this diagram is the definition of the angle Phi. Pgamma seems to be the polarization vector in the rho0 recoil-nucleus CM frame, and presumably Pgamma has components in the x, y, and z direction in this frame. So what exactly is the angle Phi in this diagram?
  5. Also shown below is the plot from Ballam, showing the clear signature for the rho0 in the helicity frame for the Psi distribution. If we were to cut on events at the rho0 peak, then this is what we should expect to see.

Useful Links

Minutes

Attendees: David L., Beni Z., Alex A., Simon T., Andrew S., Rory M., Ilya L.

  • Meeting schedule will be shifted by one week to allow Elton to participate since he is only working every other Thursday. We decided to skip two meetings and meet next on April 21st. Important/pressing issues can be handled at weekly CPP meetings
  • We took a look at the halld_recon repository and there was one PR for the BCAL pending. This is not CPP related. Alex said he would merge it soon.
  • CTOF
    • Much of the code is in place, but Simon cannot test the digihits aspect yet since we have no data with raw hits. This triggered a larger discussion:
      • The best way to get digihits is to run the DAQ, but this cannot be done at the moment since they need a fiber optic installed in order to integrate the new crate into the trigger system. Sasha has to do this.
      • We will also need a fiber for the CTOF muon trigger. The muon trigger will use one of the TS front panel bits and will therefore show up in the fp_mask member of the trigger object. This will be useful for triggering on cosmics in the CTOF in order to check out the readout chain. This also requires Sasha. Beni will speak with Sergey and together they will encourage Sasha to get both fibers installed soon.
      • We need the coordinates for the CTOF and FMWPC in the translation table. Beni was speaking with Justin recently on a related issue regarding the scalers. Alex noted that he and Sean had created the needed structure for a single chamber as part of the chamber testing. Alex will contact Justin to pass on this structure on so it can be copied for the 6 layers of the full FMWPC.
    • Locations of the paddles in lab coordinates are needed in order to match them with track projections. We will need to get these from Tim. Beni noted that rough numbers obtained via tape measure would likely be good as placeholders for now. (possibly forever given the projected track resolution at the CTOF).
  • DBeamPhoton
    • Elton reported to David that a recent simulation he did resulted in DBeamPhoton objects only in the (new) microscope region. This suggested that the overlapping microscope/hodoscope regions may need some special handling in the DBeamPhoton code.
    • David reported and Alex confirmed that the current code was mostly written by people no longer involved in GlueX. After some discussion, David volunteered to look into it a bit more and report back at a future meeting on how and who would best address making sure the code was properly working given the physical configuration change.
  • FMWPC Timing Calibration
    • Alex reported that Sean was asking about timing offsets and resolution of the FMWPC.
      • Rory noted the hit resolution is 2-4 ns.
      • David noted that since we don't use drift times, he is likely interested in matching hits to events
      • Simon noted that the chambers can be calibrated to the leading edge.
      • Beni noted the matching will need the full range of the timing window which will be roughly 300ns.
      • Alex wrote down the relevant numbers and will communicate them to Sean.
  • David reported on the status of the DFMWPCMatchedTrack factory.
    • Changes were made that now use the DFMWPCCluster objects. Code has not been pushed to Github yet, but will be soon.
    • Some changes were made to DFMWPCCluster to facilitate matching. These included adding x/y min/max values in global coordinates. David later decided this was not the right way to do it and used an alternative method. The question came up as to whether the x/y min/max members should be removed to clean up the code or be left in just in case a future use is found. It was decided the extraneous code should be removed.
  • K+K-: Andrew reminded us of an analysis of GlueX data he reported last year that showed significant contamination of the K+K- for phi decay in the pi+pi- invariant mass spectrum in our region of interest. At the time he explored trying to remove the K+K- events with some strategic cuts. These did not lead to a clean spectrum so more work was (and still is) needed.
    • Simon offered to include K+K- kinfit values in his existing class that already has e+e- and pi+pi- values.
    • Alex noted that for his exclusive rho analysis, he had success cutting on the kinfit confidence level. It was not clear if this would work for inclusive events, but it might given the heavy Pb target CPP will use.
  • We only briefly touched on monitoring plots. Rory had sent some suggestions in an e-mail last week and David copied these into this meeting page for easy reference.
    • Rory noted that Elton responded to his question on the helicity frame with details on how to calculate values in it.
    • Andrew noted he has code that does transform into the helicity frame and offered to provide it for the monitoring plots.

Action Items

  • Merge in BCAL PR (Alex)
  • Contact Sergey + Sasha about installing fibers soon for CTOF+FMWPC readout (Beni)
  • Provide Justin with data structure for FMWPC addition to Translation table (Alex)
  • Add values with global coordinated of CTOF paddles to be used for matching (Simon)
  • Review DBeamPhoton code and report back on needed changes (David + Elton)
  • Finalize list of FMWPC calibration constants and create items in CCDB (Alex)
  • Add DCTOFPoint objects to DFMWPCMatchedTrack (David)
  • Provide FMWPC timing calibration numbers to Sean (Alex)
  • Remove x/y min/max from DFMWPCMatchedTrack and push changes to GitHub CPP (David)
  • Add K+K- to DEpEm factory of kinfit values (Simon)
  • Dig out helicity frame code for reuse in monitoring (Andrew)