[d2n-analysis-talk] Trigger Efficiency Update

[David Flay]

Hey Brad,

I talked to Kalyan on Friday, and he forwarded me a message from Jin on
how to obtain the prescales.  So I can now grab the prescales from each
run (most turn out to be 1, with the exception of the elastic 3He runs).

Over the weekend I did a run-by-run analysis.  The results are in good
agreement with the sample calculation I showed last week; however, roughly
100 runs show a T3 efficiency of exactly 100%.

So I just did a cut-by-cut study for a run with such a result (20157).

Here's what I found:

First, the 1-track, trigger 3 or 4, and VDC cuts don't affect the results
(which I expected -- as compared to no cuts at all):

============== Run 20157 Results ==============
Number of Events of Each Trigger Type:
Trigger 3: 265903
Prescale 3: 1
Trigger 4: 39
Prescale 4: 1
Trigger Efficiencies:
Trigger 3: 99.9853 +/- 0.0023%
Trigger 4: 0.0147 +/- 0.0023%

call this result the 'baseline.'

My suspicion was in the PID cuts -- so here are the results for each cut I
used (each result is using 1-track, VDC, trigger 3 or 4, <plus> the PID
cut listed):

GC ADC sum > 0 (GC fires):

============== Run 20157 Results ==============
Number of Events of Each Trigger Type:
Trigger 3: 15298
Prescale 3: 1
Trigger 4: 21
Prescale 4: 1
Trigger Efficiencies:
Trigger 3: 99.8629 +/- 0.0299%
Trigger 4: 0.1371 +/- 0.0299%

move the GC cut to cut out the 1 photopeak (GC > 300):

============== Run 20157 Results ==============
Number of Events of Each Trigger Type:
Trigger 3: 3643
Prescale 3: 1
Trigger 4: 12
Prescale 4: 1
Trigger Efficiencies:
Trigger 3: 99.6717 +/- 0.0946%
Trigger 4: 0.3283 +/- 0.0946%

GC TDC cuts:

============== Run 20157 Results ==============
Number of Events of Each Trigger Type:
Trigger 3: 3908
Prescale 3: 1
Trigger 4: 4
Prescale 4: 1
Trigger Efficiencies:
Trigger 3: 99.8978 +/- 0.0511%
Trigger 4: 0.1022 +/- 0.0511%

Pion Rejector cut 1 (E/p > 0.54)

============== Run 20157 Results ==============
Number of Events of Each Trigger Type:
Trigger 3: 11001
Prescale 3: 1
Trigger 4: 2
Prescale 4: 1
Trigger Efficiencies:
Trigger 3: 99.9818 +/- 0.0129%
Trigger 4: 0.0182 +/- 0.0129%

Pion Rejector cut 2 (L.prl1.e > 200):

============== Run 20157 Results ==============
Number of Events of Each Trigger Type:
Trigger 3: 11093
Prescale 3: 1
Trigger 4: 1
Prescale 4: 1
Trigger Efficiencies:
Trigger 3: 99.9910 +/- 0.0090%
Trigger 4: 0.0090 +/- 0.0090%

all together (GC ADC Sum, GC TDC, PR E/p, L.prl1.e cuts):

============== Run 20157 Results ==============
Number of Events of Each Trigger Type:
Trigger 3: 2290
Prescale 3: 1
Trigger 4: 0
Prescale 4: 1
Trigger Efficiencies:
Trigger 3: 1.0000 +/- 0.0000%
Trigger 4: 0.0000 +/- 0.0000%

Despite this result being exactly 1 for the T3 efficiency, I think such
behavior of the cuts is correct -- in that the T4 is S1.and.GC ||
S2.and.GC and !(S1.and.S2) -- so these T4 events could be knock-on
electrons, and would show up in the 1-photopeak.  So a cut on the GC
greater than 1.5 p.e.'s would remove a lot of those (~30%, actually). 
Similarly, the GC TDC cuts show that most these events aren't in time with
good electron events, removing all but 4 events.  Finally, the PR cuts
further support this, as those cuts are designed to remove the knock-on
electrons (the pion region of the 2D energy plot for the PR).

I just find it surprising that I have this behavior for ~100 runs (which
seems like a lot), spread out over all the runs I used from p = 0.60 to p
= 1.70.

On second thought, this run has low statistics to start with (~300k).  If
I look at a larger run (20676, ~1.4M events, p = 0.60 GeV) I get an
efficiency of 99.96%.  So maybe this is just a statistical issue...

The analysis used 216 runs.

What do you think?

Thanks,

Dave

-------------------------------------------------
David Flay
Physics Department
Temple University
Philadelphia, PA 19122

office: Barton Hall, BA319
phone: (215) 204-1331

e-mail: flay at jlab.org
            flay at temple.edu

website: http://www.jlab.org/~flay
              http://quarks.temple.edu
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