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    User name Adaq

    Log entry time 14:59:37 on December 7,1998

    Entry number 7708

    Followups:

    keyword=S1,S2 hit combinations

    Shown in the plot below are S1,S2 hit combinations (E-arm).
    The number of hits is decided based on the number
    of phototubes that have TDC data (and hence were
    above threshold and would participate in the trigger).
    Plots from top left counter-clockwise: 1) All trigger 1.
    Note the main peak at (2,2) corresponding to a left
    and right PMT on each scint plane; 2) Same as 1 but
    suppress the (2,2) peak for convenience; 3) Same as
    1, but now require that either on S1 or on S2 there was
    an overlap. The peaks at 4 PMT hits look similar to
    in plot 2, showing that they are "pure" overlap. 4) Same
    as 1, but require that BOTH S1 and S2 have an overlap.
    Now get mainly the peak at (4,4) PMT hits.

    Conclusions: The number of overlaps in the trigger
    are approx 1.5% and is as expected by geometry. No
    strong explanation here yet for the wierd VDC wire
    map valleys.


    FIGURE 1