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    User name Yi Qiang

    Log entry time 05:35:34 on February 17, 2009

    Entry number 261591

    This entry is a followup to: 261389


    keyword=More results of BB Gas Chrenkov analysis from run 1479-1482

    Those runs were taken after the PMT12 base replacement and other adjustments.

    plot 1 shows the TDC spectra of each PMT requiring single track, single
    TDC hit and large pre-shower.

    plot 2 shows the selection of mirrors, X and Y are projections assuming
    mirrors are 0.8m away from the first wire chamber.

    plot 3 shows the TDC spectra with mirror selection in addition to the
    single track, TDC and preshower cuts. The accidental background drops

    plot 4 ADC spectra from each PMTs. The red curve is supposed to be the
    signal from electron which requires single track, single TDC hit, large
    pre-shower, mirror position and coincidence cut. The blue curve is for
    background. In order to select real un-biased background events, except
    for the single track I didn't apply any cut on that mirror or PMT.
    Instead, I chose the events passing through a mirror, #j, far away from
    the interested one, #i: j=21-i. I require single TDC and position cut of
    mirror #j.

    From results I learned the following:
    1. The R-HRS side PMTs are fairly quite. The beam line side PMTs suffer
    large base/pedestal fluctuation due to higher rates.
    2. Roughly speaking, the Gas Cherenkov performance in terms of maximum
    number of photon does not vary too much (>factor 3) from mirror to
    mirror. The difference of the amplitudes is most likely due to alignment.
    3. Mirror 4 has much less events than the others may due to the event
    selection. Special attention required.

    A copy of this log entry has been emailed to: meziani, bogdanw, brads, xqian, zhangyi, posik, flay, vasulk

    Figure 1

    Figure 2

    Figure 3

    Figure 4