Optics Meeting Aug 30 2022 230PM ET

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1. Phi offsets in Holes and combined MOLLER+C12 generator results [Vassu][1]

2. New task needed: verification that the present 3.2% radiation length total thickness of the GEMS, and the 4.7% total radiation length of the trigger scintillators will not have adverse effect on the optics calibration (to close out a PDR recommendation). [David]

3. Effect of GEM resolution on reconstruction of theta, phi, and momentum. [Kate] [2]


Zuhal, Kate, David, Brynna, Vassu, Bill, Chandan, Ciprian


  1. Some overlap between 12C and Moller events especially for pass3, sector 5. Maybe need to make the three holes in sector 5 at different phi offsets like in sectors 1 and 2. Some holes are near the edges of the GEM acceptance for certain rotation positions, we worry about being where the GEM efficiency might drop (near GEM frames). Could reduce phi offsets, or adjust the rotation angles. Decide to try the latter (i.e. adjust the "rad" and "black" rotation angles). Most important to look at GEM 4 layer, since the azimuthal defocusing will have its largest effect at that layer.
  2. Discussed ways to have a first look at the effects of the radiation length of the GEMs and the TS on the optics reconstruction. First try will be to overestimate by putting all the radiation length just upstream of GEM layer 1, look at hole images for 12C and Moller, and include effect of secondaries. Later we will want to ether 1) put more realistic detector material geometry into remoll or 2) make a standalone GEANT 4 simulation with realistic GEM/TS geometry, which has as input the flux distributions from remoll for just upstream of GEM later 1, and see what deflections are observed. Note that the effect of the air (between the drift tube exit window and the main detectors will not be negligible, nor is the Al exit window (1.4% of X_0).
  3. GEM smearing results: looks very acceptable with 1 mm smearing. Largest effect is on theta reconstruction, where present smearing increases standard deviation of residuals in theta by about 25%... but in absolute terms the s.d. in theta is very small (of order 3x10^-4 rad, which is 1.5% of the mean theta). Need to quantify the effect of this on the kinematic factor (Q^2). Smearing has only tiny effect on phi reconstruction.

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Meeting ID: 972 5975 5403

Passcode: 4937

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