[d2n-analysis-talk] Scintillator Calibrations: Steps 1 - 2

[David Flay]

Hi Brad,

Over the past few days I've been working through the steps you've prescribed
recently.

What I've done is as follows:

1. Choice of 'reference' paddle, and alignment to convenient location:

I've chosen paddle 7 (considering the numbering going from 0 - 15) as my
reference
point.  I plot the paddle's time average [0.5(L.s2.lt_c[i] +
L.s2.rt_c[i])] and
align that peak to 62ns -- via making changes to the DB.  (the actual peak
position
comes out to ~62.03ns using a Gaussian fit.)

See plot 1.

2. Alignment of all other paddles:

To carry out this procedure, I consider the plot of the paddle 8 time average
subject to cuts of the form:

cut = trigger cuts + L.s2.lt_c[i]>0 + L.s2.rt_c[i]>0  + L.s2.lt_c[i-1]>0 +
L.s2.rt_c[i-1]>0

These last four cuts are used to look at events that explicitly fire both
paddle 8
and 7 => overlap.  Due to such a constraint, I need a full replay to have
enough
events to see any peak structure to the resulting time average of the
paddle in
question (~1.4 M events from replay, cuts down to ~4-5K events).

I fit this resulting plot to a Gaussian and determine the mean.  I compare
this
value to the time average of paddle 7, and make the appropriate changes to
the DB to
shift the time average of paddle 8 to match that of paddle 7.

Then, a full replay is done, and I run my script which plots the histogram
described
above to check the result.  If it's OK, I move to the next paddle.

See plot 2 for a corrected paddle time average with a Gaussian fit.

I then do this for all paddles -- for i > 7, I compare the time average
for the
paddle in question (i) to the paddle before it (i-1).  If i < 7, we
compare to the
i+1 paddle (i.e., if checking paddle 6, we cut on TDCs of paddle 6 and 7,
and so
on).

Plot 3 shows an overlay of all time averages with the same cuts mentioned
above.
Plot 4 shows an overlay of all time averages (no TDC cuts).

I found plot 4 to be strange/interesting.  But what if this cut I use is
actually just examining a tail of the full plot (seen in plot 4).

If I overlay plots 3 and 4, I obtain plot 5 (I put this in log scale so we
may see it better).  This shows there is some small 'shoulder' region 
that I was aligning that doesn't fall underneath the main peak, that would
otherwise be obtained if I'm not looking at events that fire neighboring
paddles.

Out of curiosity, I plotted the plots I usually show as a 'check' of how
things look (plots 6 and 7) -- in particular, the beta vs. track-x plot is
more aligned, due to
the S2m time average having (now) a similar structure to that of S1.  I
thought that was worth pointing out.

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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