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#### User name Ulmer

#### Log entry time 11:14:38 on June23,2002

#### Entry number 86680

#### Followups:

keyword=Left VDC tracking efficiency problem?

The plot below shows the tracking efficiency for the Left and Right spectrometer VDC's. The Left shows slope but the singles rate is only about 5kHz (kin Q2D_j40).

This slope appears in the previous two kinematic settings as well (I haven't yet checked how far back this behavior goes). Further analysis (using test_vdc.kumac)

indicates that this slope arises from the multiplicity cuts. In fact, it arises if the efficiency is defined by ANY one of the four plane multiplicity cuts (u1 and v1 cuts show very similar slopes for the efficiency and u2 and v2 are also similar though of slightly lesser slope than u1 and v1). If the efficiency is defined by u1mult>0 compared to all events, the efficiency spectrum is identically=1. If the efficiency is defined by u1mult>0.5, there is significant slope, though somewhat less than shown below. Finally, it appears that zero hits in u1 are correlated completely with zero

hits in u2 and with zero hits in v1 (as expected?). Then why, if we remove this

multiplicity cut, does ESPACE find a track at all? At the moment, I don't have answers, so thought I'd engage other interested parties with this Halog. Probably, I'm just missing something simple.

FIGURE 1