[d2n-analysis-talk] Pion Rejector E/p Problem

[David Flay]

Hi all,

So, as I was making some plots for the d2n status report just now, I've
noticed an issue: the E/p plot shows a very large spike at ~0... see the
attached plots -- for 4-pass, p = 0.60 GeV and 5-pass, p = 1.70 GeV.

Now, both plots have the cuts (for the red curve -- electrons):

GC sum > 400 (2 photoelectrons) (blue curve is for pions, so GC sum = 0)
PRL 1 and PRL 2 > 0
E/p > 0
VDC -- u1,u2,v1,v2 planes have one cluster reconstructed
removed dead time pulse
T3 cut

I was wondering if this was correlated to the spike at 0 in beta, but it
doesn't seem so -- a cut on beta (in any form) gives no changes (that I
can clearly make out, at least).

So, I've plotted beta with the cut: prl_E_P>0.01/prl_E_P<0.01... the
results are shown in the last two plots.

This in part suggests that the spike at E/p ~ 0 is due to cosmics to some
degree.

A more interesting plot is the last one -- E/p subject to a cut explicitly
on the spike in beta ~ 0. This illuminates the spike in E/p ~ 0, and shows
a pion contribution.

This could possibly suggest that my calibration of the PR wasn't that good
-- but each pion peak has been aligned for each block... so I'm not sure
what's wrong here.



-------------------------------------------------
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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