[d2n-analysis-talk] LHRS Scintillator Calibration Study

[David Flay]

Hi all,

Vince was kind enough to provide me with some starter code to get me going
on the check of the scintillator calibration.  I've edited it to reflect
the necessary values appropriate to d2n regarding cuts, etc. for this
study.

Attached are a few plots that are good indicators of how well our
scintillators are calibrated.

Each paddle has two PMTs attached to its left and right ends,
respectively. There are 6 paddles in S1, and 16 paddles in S2m.  In order
to have good timing resolution, the time offsets of these two PMTs should
be minimized.  The offsets are due to differing lengths of cabling
connecting the PMT to its corresponding TDC.

The plots, going from left to right in scint_toffs_20675_3_2_10.pdf are:

Top left: The time offset is calculated as (L.s1.lt_c[] - L.s1.rt_c[]),
and plotted against the paddle number, so that we may see how each
paddle's time offset looks.  We see that the time offset is on the order
of 1-2 ns at most for each paddle.

Top right: The next plot is the average TDC time for the S1 plane,
calculated as (1/2)*(L.s1.lt_c[]+L.s1.rt_c[]), plotted against the paddle
number.  Ideally, the average TDC time would be a straight line in this
plot, meaning essentially that the trigger won't depend on which paddle
fired (in time). This plot shows good consistency with this idea.

The same may be said of S2m. (The lower two plots). (Note, for d2n, S2 =
S2m).

The beta_track_20675_3_2_10.pdf plots beta in the upper panel, and beta
against the tracking x variable.

Beta is dependent on the time-of-flight between S1 and S2m, so it's
appropriate to see how beta looks.  We see beta is ~ 0.92 in the upper
plane.  Ideally, this should be ~1.

In the lower plane, we see that beta is approximately constant as a
function of the tracking variable x (in the Hall coordinates this is the
vertical axis).  I am concerned about the region x ~ 0.15-0.20 -- there's
a bit of a blip there.

Overall, it seems that the time offsets look good for both S1 and S2m.

It seems like beta could use some tweaking to get it closer to 1 (?)

Thanks to Brad, Vince, and Chiranjib for their insight, answering my
seemingly countless questions and help with the plots -- it's much
appreciated!

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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