User name Ulmer
Log entry time 14:02:42 on June23,2002
Entry number 86686
This entry is a followup to: 86680
keyword=Left VDC tracking effic
Figure 1 shows the tracking efficiency of the Left VDC vs. delta for Run 1759.
The efficiency is defined by the fraction of all tracked events which have all four
wire plane multiplicities between 3 and 7 inclusive. The top panel includes a
fairly tight cut on the gas Cherenkov (1000-3000) for both spectra used to define
the efficiency. The slope persists. The bottom panel includes, in addition to the
Cherenkov cut, a tc_cor cut on the reals peak (204-214). Now the efficiency appears
flat, though the statistics are much worse, obviously. As tc_cor requires a good
track, another figure was generated (Figure 2) where a tc cut was used instead.
Again, the efficiency looks fairly flat. All this appears to be consistent with Mark Jones's idea that cosmics may contribute significantly to the rate in the low count
rate regions of delta and cosmics are much more likely to mistrack. This also supports the fact that the efficiency is very high near the peak of the spectrum and drops off as one moves away from the peak in either direction.