Optics Meeting Oct 11 2022 230PM ET

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  1. (Kate) low energy photons on GEMs - possible places where root files are getting stuck [1]
  2. (Kate) theta reconstruction with scintillator ring [2]


Kate, David, Ciprian, Brynna


  1. (Kate) The addition of the 8% radiation length scintillator material in a ring only broadens the distributions of the reconstructed theta's by a small amount (12%, from sigmas of 0.35 mrad to 0.39 mrad). However, the mean of the absolute value of the residuals does increase somewhat, from 0.064 mrad to 0.170 mrad. We should probably look into this latter a bit more to understand it.
  2. (Kate) Found events in the low-energy electromagnetic process simulations that are getting "stuck" and timing out, by writing step-by-step output from GEANT 4. In the couple of cases found so far, it is very low energy electrons that are somehow bouncing around in the magnet coil or surrounding materials, but in which the electron seems to (unphysically) have no energy-loss, when these volumes are not vacuum, but have materials (G10, for example for ucoil_7). In one case the track is a 0.75 keV electron which goes for at least 84 m without losing energy, and taking >7000 steps. In a second event a 1 keV e- in the same general region (magnet coils region) bounces around for >199 steps, for a path length of 4 km (!!) eventually somehow losing energy to being 11 eV, but, again seeming not to have any standard energy loss.
    1. Is this a geometry flaw, or some problem with the libraries? Maybe we should make the magnet materials all out of kryptonite? Or maybe cut off all tracking of electrons below some energy (100 keV)? We should explore online fora for GEANT 4 to see if anyone else has encountered this sort of thing
    2. To set this in context, the range for a 100 keV electron in a material like silicon is 0.05 mm, and it falls rapidly for lower-energy electrons.

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Meeting ID: 972 5975 5403

Passcode: 4937

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