[d2n-analysis-talk] LHRS PR Pion Rejection Factor (multi-cut efficiencies)

[David Flay]

Hi all,

I've been examining over the past few days another set of cuts for
rejecting pions.  In particular, utilizing the PR layer 1 (PRL1) as an
auxiliary cut to that of E/p.  Once again, standard cuts are applied to
all histos involved in the calculations.

The procedure is as follows:

We plot E/p with an anti-Cerenkov cut (L.cer.asum_c==0).  Count the number
of events in this histogram, called Ni (below some E/p cut value, as shown
last time).  We compare this histogram to that of the same E/p plot, but
now with the additional cut on PRL1 -- that is: L.prl1.e < X.  Count these
events, called Nf. So, we have the ratio:

r = Nf/Ni.  This tells us how many pions were detected via the PRL1 cut
(below some value X).  Subsequently, this implies that for r ~ 0.99, we
will therefore reject ~99% of the pions when using the 'inverse' PRL1 cut
(that is, L.prl1.e > X).

This procedure was carried out for p = 0.6, 1.20, 1.70 GeV (at the
moment).  I have used a wide range of X values in my cuts, ranging from
100 to 700 channels.  I have provided plots for each kinematic -- (total)
cut efficiency as a function of cut placement in E/p, where the total cut
efficiency refers to the ability to reject pions based upon the combined
PRL1+E/p cut.

This method differs from that of my previous e-mail concerning the gas
Cerenkov cut in the PR to reject pions.  I could employ the same method as
last time -- seeing how many pions pass a PRL1+E/p cut in the E/p histo,
and see the contamination level -- but this method is explicitly tagging
pions through the requirement of the anti-Cerenkov cut.

I've done a quick 'back of the envelope' calculation, and both methods
seem consistent, though I would have to investigate it more thoroughly. 
It seems that both methods are just two different ways at approaching the
same problem.

I'll have a more formal discussion on Tuesday for our meeting, compiling
all the pion rejection analysis of the GC and PR detectors so far.

Dave

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

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

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

website: http://www.jlab.org/~flay
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