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    User name Yi Qiang

    Log entry time 00:28:46 on February 16, 2009

    Entry number 261389


    keyword=Analysis of Bigbite Gas Cherenkov

    The following analysis was done for mirror 6 (beam line side) using the
    data taken before Feb 15 owl's access

    The basic cuts used through out this analysis are single track cut and
    single TDC hit cut in mirror 6:

    Plot 1 shows the two TDC cut I used to select coincident events between
    Gas Cherenkov and shower: cut 1 for the shape peak and cut 2 for the
    broader structure.

    Plot 2 shows the Bigbite tracking projection to the Gas Cherenkov
    mirrors, I assumed a 0.8 m distance from first wire chamber to these mirrors.

    Plot 3 shows the mirror location with coincidence cut 1. We can clearly
    identify mirror 6 and a graphic cut was defined for this mirror. I also
    defined a cut for mirror 12 which is far away from mirror 6.

    Plot 4 shows the mirror coverage with coincidence cut 2. Looks like that
    this coincidence is from the events mainly hitting the two near mirrors,
    5 and 7, instead of mirror 6.

    Plot 5 shows the TDC spectrum of mirror 6 with geometric cut on mirror 6
    and the background basically goes away.

    Plot 6 shows the TDC spectrum of mirror 6 with geometric cut on mirror
    12. This time the coincidence peak disappears.

    Plot 7 shows the ADC spectrum of mirror 6 with geometric cut on mirror 6
    and various TDC cuts. With coincidence cut 1, a distribution with fairly
    large number of photon electrons shows up. With coincidence cut 2,
    because these events share the number of photon electrons with other
    mirrors, the peak moves to the lower side. Cutting outside of both
    coincidence windows gives pedestal and background only.

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

    Figure 1

    Figure 2

    Figure 3

    Figure 4

    Figure 5

    Figure 6

    Figure 7