• Main INDEX
  • Monthly INDEX
  • PREV
  • NEXT

    User name R. Michaels

    Log entry time 00:58:31 on June11,2004

    Entry number 125303

    This entry is a followup to: 125294

    keyword=Trig biases make alignment difficult

    Looking at the blobs in X-Y distribution (fig1), and cutting near
    one (red box) or the other (green box) we get momentum spectrum
    in fig 2 (the units are MeV/c). Equivalently you get the peak
    near 0 in momentum if you simply require a large ADC signal in
    HAPPEX detector. This is not elastic/inelastic spectrum, this is
    a trigger bias effect. The stuff that makes scint triggers gets
    blocked by the HAPPEX detector (it seems to block a lot more than
    during our first experiment). And the stuff that make T2 is confined
    to the HAPPEX detector. So you get distortions, edge effects, a
    real mess.

    How to align ?

    There are two possible ways:

    1) Can put a large scint that fills the whole acceptance IN FRONT
    of the HAPPEX detector (how about S0 ?).

    2) Can move the elastic peak to -3%, -2%, +2%, and +3% and deduce
    from S2 triggers and the shadow of HAPPEX detector where 0% is.
    These data are available from optics, but probably want to do it
    without sieve. It is not much different from our original plan.

    FIGURE 1

    FIGURE 2