Hello John,
I think our speculation about triples (showers) is further corroborated
by the fact that we also see grass only to the left of the retime-OR
peaks. This is what would happen if a single paddle gets an accidental hit
just before the L/R coinc trigger. And we know it happens only at the
edges of the measured 40-45 ns coinc window.
Of course the first signal to hit the tdc after the common stop is the one
that will stays in the data stream... even if it does not relate to the
true coinc trigger! In this case the TS is strobed early and the time
becomes the time of XMLU-out leading edge, but of course, even if this
happens we shouldn't lose good events since there are no good events in
a shower.
For elastics, the random events need only to arrive a few ns earlier than
the "good" forward elastic electron: this seems to happen only with
one paddle (3R, but more for 3R-L13 events than 3R_12L coincs).
Note also the "grass" extends only to a few ns.
Finally, as you know, the fast-fast (or e-e) events go away with
_ adc cuts
_ slits in
which again makes sense.
Some more analysis on monday, including field on data and making
these randoms go away with a cut on the backward scintillators, to make
ealry events from upstream go away. Stay tuned
-- tancredi
________________________________________________________________________________
Tancredi Botto, phone: +1-617-253-9204 fax: +1-617-253-9599
research scientist MIT/Bates, 21 Manning Av Middleton MA, 01949
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
On Fri, 9 Aug 2002, John Calarco wrote:
>
> Tancredi,
>
> I am speculating that the purely accidental regions (1 and 4) on the
> 2-D t_left vs t_right plot may be due to the accidental firing of one
> of the last few TOFs on either side in true coincidence with one of
> the 2 displayed TOFs but in accidental coincidence with the other.
> Since these are backward relative to the target, they are closer to
> any upstream source of showers and would thus fire early, causing
> the TDC time associated with their retiming strobe to be late, i.e
> higher channels.
>
> John
>
>
>
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