Commissioning Module Occupancy
The plot below shows the initial occupancy and - chip offset
vs chip number for data run 004 for the commissioning module.
The algorithm used to calculate the chip thresholds for this
Thresh = offset + 3 * offset dispersion + 4 * noise
where offset, offset dispersion, and noise were determined
on a chip by chip basis. The plot clearly shows an anti-correlation
between the occupancy and the chip offset. This suggests that
the chip offsets, determined from three threshold scans
at different charge injection values, are not the real offsets
for the chips. The real chip-to-chip offsets probably have a much smaller
spread than what is found from the linearity fits.