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    User name A. Deur

    Log entry time 18:13:47 on July29,2003

    Entry number 108004

    This entry is a followup to: 107741


    keyword=origin of the pions

    The pion appears to originate from the glass window of the target getting their way around the collimator (due to either target/collimator misalignment or multiple scattering or hadronic scattering... ). In fig 1, the top plot shows y_t with anti-PID cuts, for a He3 production run (top left) and a empty ref cell run (top right).
    There is two peaks: The prominent one is at the glass window location. The second peak is at the top of y_t acceptance and it is actually an artefact. It is actually the tail of the first peak that is enhanced by the sharp rise of the y_t acceptance.
    We can see this if we deconvolute the y_t acceptance from the plots. This has been done in the bottom plots (left for He3 run and right for empty cell run). Then only one peak remains. The deconvolution is simply done by dividing the spectra by a y_t spectrum (with PID cut) corrected from glass contamination.

    So it appears that the pions come from the upstream glass window while we cannot see any from the He3 or downstream window.

    FIGURE 1