To clarify VZ problem reported in last log, more runs (1752-1764) are taken to scan beam vertical (y) positions. For each run, vz is constructed with LHRS and its preliminary database. Quality of reconstruction for central ray was demonstrated in Halog 329242 (http://www.jlab.org/~adaq/halog/html/1007_archive/100701033232.html). For each run, there 4 plots are generated: * Left top: track angle at target (tg_th:th_ph) * Right Top: momentun deviation (tg_dp) * Left Bottom: vertex z vs tg_ph correlation * Right Bottom: vertical raster VS vertex z +y is up As Fig. 1, when beam was left at y=0, it's hitting some thick target at vz=~-15cm. Only down going particle was seen. Naive guess it's holder of upstream carbon foil. For Fig. 2~3, beam was moved to -3 and -5mm, vz=-7.5cm(?) and +15cm foil has became more and more clear. Also, angular coverage has became more symmetric. Therefore, a naive guess is when beam is at y=0, it's hitting foil holder. We should take more data at y=-5mm to get better vertical angular coverage as well as avoiding hitting the foil holder. At y=-4 mm, more data was taken with raster off, which was shown in Fig 5(LHRS) and Fig6 (RHRS). It seems vz peak at ~z=0- was much stronger than downstream carbon foil. They both showed on RHRS VZ:tg_ph correlations, although less clear. It still confuses me why, 1. beam y=0 was OK for 1 pass elastic run on LHRS, but now seems hitting holder. 2. There are only two vz peak at run 1762. One stronger than other. Could the stronger one be two foil or we lost the upstream carbon foil? 3. Also for run 1762, there is a shadow on the small vz side (more upstream).
Figure 1: Run 1752, Beam y~0
Figure 2: Run 1761, Beam y~-3mm
Figure 3: Run 1762, Beam y~-5mm
Figure 4: Run 1764, Beam y=-4mm, Raster off
Figure 5: Run 1764 for R-HRS.