• Main INDEX
  • Monthly INDEX
  • PREV
  • NEXT

    User name brads

    Log entry time 22:52:15 on May19,2008

    Entry number 238888


    keyword=Coin. time mysteries and musings

    I've been trying to understand the structure in the bit3[0] variable. This is supposed to be the HRS timing(==T3) stopped by the L1A (which is timed off BigBite==T1).

    This is all for Run 1324.

    Looking at the red histo (DL.bit3[0]) starting at bin zero we have:

    0) Hits I do not understand running from 0 to 360. These are supposed to be coincidence events -- how do we get hits outside the coin window?

    1) A ~75ns(?) width of T1 at the coincidence AND generating the gap between 375--525. Those events get self timed and pile up in the spike at 465. (75ns seems kind-of wide though...)

    2) "Random" background between 525 and the coin peak.

    3) Coin. peak broadened by dT between the HRS paddles and other uncorrected, but understood corrections. (ie. view bit3 vs. gold.p)

    4) More random background. Why lower than background (2)? (This is what caught our eye at the start.)

    5) Spike at 760 is EDTM.

    6) Coin window closes at 800. Width of coin window is 800-520=280 channels => 140ns. That corresponds with the width of the HRS T3 at the coin. AND gate.

    So, I need some help:

    Why does the "random" background so much less on the right (earlier times) of the peak vs. the left (later times) of the peak.

    The hits in point (0) above must have BB as the L1A so the must be T1 singles. Why the structure? I guess the peaklet on the right (around ch 320) part of the coin. peak that gets chopped off when the coincidence AND is made and T5 steals the show? (This may be supported by the suspiciously good match between the black and red histos -- black is just the red + 140ns.) That's a really non-flat background between 0 and 300 though... Somebody with more experience than I needs to point out that another (non-elastic) reaction channel is kicking in and generating slower protons. Anyone?

    FIGURE 1