[d2n-analysis-talk] S2m Timewalk (Complete?)/ PID Technical Note, Version 4

[David Flay]

Hi all,

I wanted to give an update on what I've done since our last meeting, and
have been wrestling with, for the S2m timewalk.

I investigated the plot of the RF time vs. S2m paddle number, and aligned
its structure, via changing the time offsets in each paddle for the L and
R PMTs.  Before and after plots are the first two plots attached.

Now, as I understand it, the RF clock drives the RF in the accelerator,
such that the CW beam is pulsed with a 2ns period.  Therefore, if we look
at the RF time (ns) vs. S2m paddles, we should see (ideally) each paddle
seeing the RF time at about the same time => a horizontal line.  This
implies that each paddle experiences the RF pulse at roughly the same
time... is this the correct understanding?

Now, making the adjustments to the time offsets for both the L and R PMTs
makes the software correction for such a phenomenon.  However, adjusting
the time offsets to make the RF time vs. S2m paddle look nice invariably
affects how the S2m time average vs. track-x looks (see third plot).  It
does <not> affect the time offsets vs. paddles, since my corrections were
applied to <both> L and R PMTs for each paddle, as previously mentioned.

So this brings me to my main question/point:

While this all seems very nice -- it doesn't necessarily help in terms of
the S2m time average vs. track-x -- which clearly affects how beta is
calculated.  I'd like to say I could go back and fix the time avg. vs.
track-x plot, but if I make any adjustments, it will most likely throw off
the RF time vs. S2m paddle plot all over again.

Personally, I feel like the more important thing to pay attention to is
how beta is constructed -- and hence the plot of S2m vs. track-x.

While this effectively corrects the timewalk, it certainly changes other
things as well -- which I don't think can be fixed by running the
optimization on S2m for the time offsets/time averages.  It seems like
I'll be going in circles...

So -- is there anything further to with this?  Or, should I reset my time
averages so that beta is calculated properly, with respect to the time
averages in S1 and S2m?

Thanks for any insight/ideas,

Dave

P.S. -- I've also updated my PID Technical Note with all calculations
implemented in an appendix section at the end:

www.jlab.org/~flay/thesis/tech_notes/eff_note.pdf

I'll eventually add in the elastic study as well; for now, this contains
all the data from the production kinematics.


-------------------------------------------------
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
-------------------------------------------------
-------------- next part --------------
A non-text attachment was scrubbed...
Name: s2m_rf-paddles_20676_4_19_10.png
Type: image/png
Size: 21585 bytes
Desc: not available
Url : https://mailman.jlab.org/pipermail/d2n-analysis-talk/attachments/20100422/f7e59f99/attachment-0004.png 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: s2m_rf-paddles_cor_20676_4_19_10.png
Type: image/png
Size: 22550 bytes
Desc: not available
Url : https://mailman.jlab.org/pipermail/d2n-analysis-talk/attachments/20100422/f7e59f99/attachment-0005.png 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: scint_toffs_20676_4_21_10.png
Type: image/png
Size: 37104 bytes
Desc: not available
Url : https://mailman.jlab.org/pipermail/d2n-analysis-talk/attachments/20100422/f7e59f99/attachment-0006.png 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: beta-track_20676_4_21_10.png
Type: image/png
Size: 37625 bytes
Desc: not available
Url : https://mailman.jlab.org/pipermail/d2n-analysis-talk/attachments/20100422/f7e59f99/attachment-0007.png