Optics Meeting Mar 13 2024 1100AM ET

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Agenda

1. database update [Bill [[1]]]
2. Optics Fit Update [Vassu][2]

Attendance

1. David, Kate, Bill, Vassu, Sayak, Tyler, Zuhal, Buddhika, Ciprian, Andrew, Juliette

Minutes

1. (Bill) Discussion on detector numbering scheme (important for MYSQL database as well as remoll). Decide to adopt a GEM numbering scheme that tracks the magnet coil numbering: detectors start with 1 (not 0), increase as one goes clockwise when looking downstream. The first GEM number (and first Trigger Scintillator number) would be in its "open sector" measurement position (starting location) between toroid magnet coil 1 (which is the first one in the clockwise direction from beam left, i.e. it is at a small +x and a small positive y location) and coil 2. Call this the "zero degree" rotation angle for the GEM rotator. The 28-fold pion detectors also start in the same azimuthal location. We don't know about the Main Detector numbering scheme. The ShowerMax detectors are not matched the pion detectors at present in remoll, but we can plan on asking for that to be changed.
2. (Bill) Discussed ideas for information for the database. In the run-by-run part of the database want 4 angular positions to be defined - the 0 degree, two intermediate positions, and then one position which is a complete sector (2pi/7) rotation from the original. Perhaps they can just be labeled as "A", "B","C","D" rotations. Vassu notes that the intermediate positions may not be at exactly steps of (2pi/21), as we want to enure that all relevant sieve hole images will be clearly seen in each rotation (each sieve hole's image must be clearly seen in active GEM area for at least one rotation angle). We don't need to specify exact rotation angles now, but we should look at this again now that we have the final sieve hole pattern defined. Will probably eventually host the database at JLab behind the gateway after construction of the GEMs, so it can be easily used and updated during the experiment. Would want a mirror site off-site from Jlab.
3. (Vassu) new simulation runs with mew 12C foil locations are done. Initial fits with combined data from all 21 sieve holes + 3 C Foil locations and 4 beam energies (4 passes). Only considering the non-radiative events for obtaining the fit function, using a tight (2 MeV) deltaE cut to select non-radiated events. In the slides the blue points are the actual events, and the orange are the predicted values from the fit. We see a definite trend to the theta-residuals, where their centroids vary monotonically depending on which foil the track came from. Discussion - since we can determine the v_z, knowing the hole (to get radial location at the collimator) and the GEM_R, can we combine these to get the foil, and then use this as an additional input to the fit to get rid of this trend?
4. (Vassu) Revisited attempt to apply the fit function to Moller events from full lH2 target, no sieve holes, this time with the theta corrected for the raster's effect. Here all events that hit the main detector are used. See around 1.1 mrad sigma for theta, with a bias (offset) in the mean of -0.4 mrad. Definite "s-curve" shape to a plot of sieve_r vs. residual, which suggests that this should be able to be correctable. Should look at the subset of events that are in Ring 5 (Moller ring).

Meeting link information

See email invitation, or contact David Armstrong, Kate Evans, or Jennifer McAllister for Zoom link