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    User name Bob/Youcai

    Log entry time 01:00:11 on November 30, 2008

    Entry number 251382

    This entry is a followup to: 251164


    keyword=hit rejection on RICH

    Youcai and I have been looking at some recent RICH data.

    The number of data rejected in recent runs is, by category

    1. Too many hits: rejects 7 to 9% (it was higher for the higher HV)
    2. Timeouts -- a negligible loss (ca 0.02%)

    At present we're rejecting around 7% of data. Note, it is rejected
    by the DAQ --> lost forever.

    Before the T/H scan we were losing about 1%. Youcai thinks this is
    because we have more noise now. Bob (a non-expert!) thinks it's
    hard to believe that the "noise" depends on T/H.

    If the experiment is worried about this we might:

    Try a few runs with the cuts turned off but the data flagged.
    This would tell us:

    a) The trade-off of deadtime increase (we already know it will go up,
    Youcai thinks it will go up a huge amount).

    b) The nature of the rejected events -- are they even analyzable ?
    (if they are very noisy they may not be).

    No strong opinions from us, but the experts should be informed.

    A copy of this log entry has been emailed to: camsonne@jlab.org,iodice@jlab.org