[d2n-analysis-talk] Spike at E/p=0 [SOLVED]

[David Flay]

Hi all,

So a few weeks back, a red flag went off in my head when I saw a spike at
E/p = 0 when I was making plots for Diana for the write-up.

I've gotten around to taking a look, and here's what I found:

1. There are spikes at the ADC sum (in PRL1 and PRL2) at zero.

2. There is a considerable amount of entries at kBig (i.e., 1e+38) in the
ExTgtCor_L.p variable (the extended-target corrected momentum, used in the
prl_E_P variable.)

See the attached plots.

The first two plots show the ADC sums for PRL1 and PRL2 respectively. 
Each has just the ADC sum plotted (in black) and with a cut on E/p ~ 0 (in
red).

The third shows ExTgtCor_L.p -- we can see entries at very large values of
p.  The red line shows a cut on E/p ~ 0; the blue shows a cut requiring a
signal of zero in the ADC sums of PRL1 and PRL2.

Based on these plots, it's clear that we'll need to cut on the ADC sums
and ExTgtCor_L.p variables in order to remove the spike at zero, as these
are not good events.

The last plot is E/p with modest electron cuts (in black) and  with the
additional cuts (in red):

(L.prl.asum_c>0)&&(L.prl2.asum_c>0)&&(ExTgtCor_L.p<5)

(I choose the value 5 in the last cut, since that is well outside of our
momentum bins on the LHRS.)

So therefore, in the future as we look at E/p one <should> include such cuts.

Would it make more sense to just include these cuts on E/p in the cut
definition file for the replay?

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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