Π polarizability Software Meeting Apr 21, 2022

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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
   • MC Event Files

4. FMWPC Library
   • DCPPEpEm - Kinematic Fit values
   • DFMWPCHit - Calibrated hits
   • DFMWPCCluster - Clusters in individual FMWPC chambers
   • DFMWPCMatchedTrack - Tracking info with matching data objects in downstream detectors
   • 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
   • FMWPC_online: Occupancy
   • FMWPC_Performance: Full recon resolution/alignment and efficiency
   • Rory suggestions (see below)
   • Software versions on gluons (ROOT, halld_recon)

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.