General Meeting Summary 4/9/15

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  • Labeling of the crystals
  • Spring 2014: crystal #1-10 (results below are from measurements performed after the Idaho irradiation tests)
  • December 2014: crystal #11-15 (had not been measured before)
  • Longitudinal Transmittance
  • Crystal #14 has strange behavior above ~500 nm; this observation does not seem to be a feature of the experimental setup
  • Crystal #12 also shows differences in transmittance from the other crystals when looking specifically at wave lengths 370 nm and to some extent 420 and 500 nm
  • Note that crystal #9 longitudinal transmittance is consistent with the other crystals. This is different from what is observed for the transverse transmittance
  • Transverse Transmittance
  • Crystal #9 transmittance is lowest
  • Crystal #8 behavior is different from the other crystals
  • General result from this transmittance test: ~20% of the entire set of crystals does not meet specifications
  • Additional observations regarding and tests with the crystals returned from the Idaho irradiation tests (#1-10)
  • Some of the crystals seem to retain a brownish color, in particular crystal #2 (this is one of the crystals being sent to Rainer)
  • Test of curing system - difficult to reach a conclusion
  • ACTION ITEM: make a table of all crystals with transmittance results at specific wavelengths, e.g., 370 nm, 420 nm, and 500 nm
  • Crystals to be sent to Rainer: #2, 3, 6, 8, and 9
  • Shipping expected by 4/10


  • Uses NH3 target, two NPS type detectors to detect the lepton pair, and a combination of tracker (~3mm scintillating fiber) and hodoscope to detector the recoil protons
  • Initial simulations have been carried out and geometry of experimental setup has been determined. Note that the detector configuration in Hall C is flexible and can be optimized, i.e., detector placement
  • Low momentum protons
  • Acceptance: studies ongoing to estimate the effect of target high field on proton deflection - implementation of magnetic field maps in the simulation. Initial studies show that angle is on order 1-2 degrees and so protons will make it out of the target
  • Reconstruction of the recoil proton - impacts resolution. Ongoing studies to parameterize the acceptance to estimate the impact on the data.
  • TCS event generator
  • Based on VGG model; modifications include options for electron or real photon
  • Initial results show a ~20% transverse target spin asymmetries
  • Fits for physics case have been started. To estimate the impact of the data on these fits need: 1) error bars, 2) luminosity per day, 3) target length, 4) acceptance for the desired binning (limited theta for a given phi angle may have an impact on the projected asymmetry)
  • uncertainty sources include statistics and bin width. Suggested bin width in t is less than 0.2 GeV/c^2 since the cross section depends strongly on t


  • TCS LOI for PAC43
  • Crystal studies at JLab and Giessen
  • Other...