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    User name Seonho Choi

    Log entry time 19:35:48 on July28,2003

    Entry number 107741


    keyword=More pions than expected?

    I checked a few more runs as regard to suspected performance of Cerenkov in recent runs. It shows that almost of half of the events from run 2946 have NO Cerenkov mirror fired. To figure out if it is hardware problem, I have replayed a few runs (2823, 2841,2900,2946). The first plot shows number of mirrors fired. Run 2823 was taken with Carbon foil while the rest was taken with He3. The spectrometer momentum setting was decreasing with run numbers for He3 production run. As the energy loss increases, the number of events with 0 mirror fired increases. For run 2946, I have checked preshower vs shower plot with cerenkov cut. The second plot shows blue for no Cerenkov cut at all and red with cerenkov cut (cer<100). From this plot, it seems that zero Cerenkov events are consistent with pions.

    FIGURE 1

    FIGURE 2