[d2n-analysis-talk] LHRS Beta: A 'Manual' Approach

[David Flay]

Hi Brad,

I've been working on some code to construct a 'manual' beta.

I start with constructing the time averages for S1 and S2m:

I first impose all cuts (that is, trigger, VDC, GC and PR cuts for good
electrons).  Then I see (for each event) if there is hit in the S2m
paddles within the range 61 +/- 5 ns.  If this is satisfied for paddle k,
I then look for a hit in S1 with the requirement that paddle k in S2m
fired, subject to the S1 time to be 55 +/- 5 ns.  When this condition is
satisfied, I fill the S1 and S2m time average histograms with 0.5*(t_L +
t_R).

Ideally, we would like to see that only 1 paddle fires in S1 for a given
S2m paddle.  Sometimes, we get multiple hits -- that is, multiple paddles
in S1 fire (for instance, paddles 1 and 2 in S1.)  This makes sense to me
where I can imagine a trajectory of a particle that goes through the top
of paddle 1 and through the bottom of paddle 2 in S1 enroute to say,
paddle 4 in S2m.  Also, the opposite can occur: paddle 2 fires in S1,
which turns out to fire paddles 6 and 7 in S2m.  For now, I've kept such
events.

I do find it odd that sometimes there is a hit in S2m, with as many as 4-5
hits in S1 (that is, paddles 1-4 fire, for instance).  I found this
strange, and I'm not quite sure how this can happen, outside of light
maybe leaking from one paddle to another?  Such events are usually
discarded as of right now.  I'm thinking of removing such events entirely
(as of right now, they are accepted if, for instance, we have a hit in
paddle 1 in S1 that passes the conditions on the time, and has a
corresponding hit in the given S2m paddle, while hits in S1 paddles 3 and
4 for that same S2m paddle are rejected based on their times).

I think this method is pretty good, but I am concerned about my
requirement of the S2m/S1 paddles having times within +/- 3 ns.  It seems
to me to be like an artificial cut imposed on the data.  However, maybe it
isn't too bad of a thing to have, since the electron cuts narrow down the
S1 and S2m distributions to single peaks, with widths of 1ns and 700ps,
respectively.

See attached plots for the S1 and S2m time averages, and their time
difference.

If you're curious to see what my code looks like, it's here:

/home/flay/d2n_analysis/d2n/d2n-replay/replay/scripts/LHRS/scint/scint_calib/MyBetaAlt.C

What do you think?

Thanks,

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






-------------- next part --------------
A non-text attachment was scrubbed...
Name: s1-s2m-avg-times_manual_20676_10_22_10.png
Type: image/png
Size: 19955 bytes
Desc: not available
Url : https://mailman.jlab.org/pipermail/d2n-analysis-talk/attachments/20101022/8f250218/attachment-0002.png 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: s1-s2m-time-diff_manual_20676_10_22_10.png
Type: image/png
Size: 17385 bytes
Desc: not available
Url : https://mailman.jlab.org/pipermail/d2n-analysis-talk/attachments/20101022/8f250218/attachment-0003.png