[d2n-analysis-talk] Strange Trigger Problem for 20090206 Directory

[David Flay]

Hi all,

I've run into a rather strange issue that I can't solve at the moment.

While Optics runs with a multi-carbon target seem to come at a premium
(with a decent amount of events), I've managed to find a few that I'd like
to take a look at.  They are runs 20076, 20077, 20078.

When I plot these, a trigger type cut of the form:

(DL.evtypebits&(1<<3))==(1<<3)

blows away all the entries in the histogram.  I've checked on a cut-by-cut
basis, and I've narrowed it down to this one.  Now, I immediately
invesitgated the db_DL.dat file to check on the crate mapping, etc.  They
match up with the rest of the directories -- to my knowledge, after going
through the Halog, there were no hardware changes w.r.t. the triggers, or
anything else for that matter.

I plotted DL.LT3, and there is a histogram.  Now, more importantly, I
plotted DL.bit3, and it apparently doesn't even exist -- hence the bitwise
operation doesn't work.

For a refresh of what these values are -- from my 'Triggers Revisited'
e-mail a while back:

"In particular, I was discussing the variables DL.LTN, DL.bitN with Kalyan
over the past few days, and he was telling me that LTN refers to the TDC
of the trigger before the L1A, while bitN corresponds to TN after L1A such
that it refers to the time trigger N arrives at L1A (essentially, also,
bitN is the prescaled version of LTN).  In the case that ps=1, the ratio
of the number of events indicates the livetime (so the deadtime would be 1
- livetime)."

So, I checked the same plots against run 20676 (20090313 directory) and
both plots exist, and hence, my trigger cut works.  I find this confusing,
and to not make much sense, considering the DL class is identical for both
cases.

Any suggestions?

Thanks,

Dave


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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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