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| − | Participants: Curtis, Mike (CMU) Eugene, Beni, Luke, Cody, Simon, Nick, Naomi, and Lubomir (JLab). | + | Participants: Curtis, Naomi, Mike (CMU) Eugene, Fernando, Beni, Luke, Simon, Nick, Chris, Vlad, Sergey, Amanda (detector group), Tyler (detector group), Pablo (detector group), and Lubomir (JLab). |
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| − | == Run status == | + | == Detector updates == |
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| − | - Simon showed results for two-track vertices from straight track data (see the logentry). We first discussed the two stripes on the 2d plot - r vs z of the vertex position. The upstream one is at the downstream CDC plate. The other stripe is in the middle of the first package (not clear why?). This may indicate background from photons(?) stopping in the CDC plate that has an inner radius of ~10cm; for r<10cm the photons are stopped in the first package. Eugene: e+/e- from the photon conversion can't be separated without magnetic field. | + | - CDC has been successfully fixed after the "near-miss" [https://logbooks.jlab.org/entry/3397702 event]. |
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| − | - Second part of Simon's results: projections on z. The positions of the target walls and the scattering chamber, as defined by the FDC with straight tracks, are off by almost 1cm as compared to the results when using the CDC with magnetic field. Later Simon included FDC-only track with magnetic field and confirmed an offset b/n FDC and CDC by about 8mm.
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| − | - Lubomir showed comparison b/n the FDC currents with full/empty target without magnetic field and 3.4mm collimator. The ratio is 2.4, to be compared to 1.4 we had before with magnetic field and 5mm collimator. The FDC currents when normalized to the active target with 3.4mm are about 20% higher than with 5mm collimator, indicating additional background not related to the collimator hole. Lubomir also showed how the FDC currents change with the magnetic field (see logentry): from 0 to 450A the currents decrease by a factor of ~4.5. There's additional factor of 5 from 450A to 1200A, so in total ~22. This is to be compared to a factor of ~40 from the spring of 2015, also indicating some extra background that we have now.
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| − | - Latest FDC wire resolution (see plot above) obtained with straight tracks is a little better than a year ago, when we had half the energy. Most likely this is due to the higher momentum of the tracks. The efficiency of the chambers (third package shown as an example) is ~90%, lower than the last year's 95%. Needs to be studied, could be a timing issue.
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| | == fADC125 == | | == fADC125 == |
