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    User name Kai

    Log entry time 05:56:35 on November 20, 2009

    Entry number 301240

    This entry is a followup to: 301203


    keyword=Hypothesis of the pion path problem

    From Fig1 and Fig3, we see that the pion path on the right arm has more serious problem. The shape of the pion rate in right arm each group is good, but narrow one has a long tail in the high rate region. My guess is that it is because the noise piling up on the signal that pass the Discriminator Low-Narrow brings the larger counting rate here. And the reason why we don't see that in the wide path is because the output of Discriminator Low-Narrow go as the input of the Discriminator Low-Wide which has 100ns deadtime. From the Fig2 which is the 2D ps:sh with TDC pion narrow cut on the right arm, we can see clearly that the cut region is small and unclean so that it is highly possible some noise could contaminate into it.

    While on the left arm Fig4, the DL cut is much more clean than that of the right so that we don't see this problem. Moreover, I agree that the timing between pion veto and pion signal might be also another reason that can cause the trouble.

    Several days agao, my suggestion of lowing the threshold of the pion discrimintor was due to the consideration that our current pion efficiency is low, which is about 30% on the left and 60% on the right. But if choosing between efficiency and clean, I would definitely choose the later.

    A copy of this log entry has been emailed to: xiaochao

    Figure 1

    Figure 2

    Figure 3

    Figure 4