User name riordan
Log entry time 18:05:13 on March 22, 2006
Entry number 167817
Followups:
keyword=Elastic Detection and Proton Detection EfficiencyHere are my results for determining the efficiency in detection of
elastic events and detection of protons from those elastic events in the
neutron arm.
In all of these plots there was a cut on the preshower energy variable >
400 to reject pions and a cut on the focal plane track x of +/- 0.5m
where we have had difficulties fitting a momentum. This area constitutes
about 70% of the area of the first chamber. The runs used were 71%
combined of the total runs 3088 and 3089, which were both 0.5 microamp
runs with prescale factors of 1 for both T2 and T3. We expected a rate
of about 1.5Hz/microAmp at this kinematic and expect about 4050 elastic
events in what was analyzed.
To determine the number of elastics in our peak we did a fit to the
background and the peak (the upper curve) and then integrated over the
elastic peak (the lower curve). Inset to the plots are the number we
found in the peak and ratio to the 4050 expected events in parenthesis.
In figure 1, the first plot shows the raw number of elastics as measured
by BigBite using no information from the neutron arm. The rest of the
plots are with combinations of cuts on the neutron arm time of flight and
the coplanarity as determined by the x position of the neutron arm and
the x position as measured by the BigBite shower. These two cuts roughly
agree and overlap with each other. The ratio between what is measured in
the neutron arm and BigBite gives us a proton detection efficiency of
about 60%.
Figure 2 is working with just the BigBite arm (the first plot here is
identical to the first plot in figure 1 for reference) with cuts done on
event type. BB Singles are defined when the event type 2 bit is set.
Coincidence is defined by the event type 3 bit being set. Pure singles
are type 2 bit set and type 3 bit absent.
We don't lose as many events cutting on type 3 as we do cutting on
neutron arm variables, suggesting that we may not be looking entirely in
the correct places for neutron events, suggesting the 60% proton
efficiency as a lower limit. Further analysis on the neutron arm and
what caused the triggers in these events should (hopefully) bring this
number closer to 80%.
The last plot in this figure for the pure singles tells us that for a
significant portion of the time, our coincidence trigger is properly
identifying coincidence events as coincidence.
Figure 3 is identical to figure 2 except a cut on the neutron arm time of
flight as been applied. These plots agree with the plots we saw before
and the last plot of figure 3 enforces that we are not seeing protons
when we do not have a coincidence trigger a majority of the time.
Figure 1
Figure 2
Figure 3
