Hi Brad and Diana,<br><br> I am looking at run 2060 for both the TDC T2 timing correction and for the 3He 4-pass run that has mostly one track events. The plot I have here of run 2060<br><br> <a href="http://jlab.org/~posik/d2n/BB/tracks/4pass_tracks.png">http://jlab.org/~posik/d2n/BB/tracks/4pass_tracks.png</a><br>
<br>Has no cuts. I just plotted the BB.tr.n variable. But if I put a T2 cut on it, the one track events are still small compared to the 0-tracks.<br><br><br><br><div class="gmail_quote">On Tue, Mar 23, 2010 at 5:56 PM, Brad Sawatzky <<a href="mailto:brads@jlab.org">brads@jlab.org</a>> wrote:<br>
<blockquote class="gmail_quote"><div class="im">On Tue, 23 Mar 2010, MATTHEW R POSIK wrote:<br>
<br>
> Here is the link to the plots that I refer to for the t2 timing:<br>
><br>
> <a href="http://jlab.org/%7Eposik/d2n/BB/trigger/t2_walk/t6_timing/">http://jlab.org/~posik/d2n/BB/trigger/t2_walk/t6_timing/</a><br>
><br>
> I took a look at the timing on the TDCs. Your explanation makes a lot<br>
> of sense. I plotted a corrected TDC 03 to carry the T2 timing and<br>
> also show the TDC with no T2 timing correction (corrected_TDC03.png<br>
> and uncorrected_TDC03.png). As you can see the peak is much narrower<br>
> and has more events under it. But there seems like there may still be<br>
> a little bit of a shoulder to the right of the dominate peak. This<br>
> may be related to the self-timing peak that I chose. There seems to<br>
> be more than one peak in the DBB.t2 trigger (t2.png), I selected 560<br>
> as my self-timing peak, but I am not sure that this selection is<br>
> correct.<br>
<br>
</div>I will admit that I don't really understand the DBB.t2 histogram. Self<br>
timing spikes are typically 1--2 bins wide -- ie. more like the spike at<br>
bin 200 than the ones out >500...<br>
<br>
The Cerenkov TDC peak does look better though, so the spikes at >550<br>
are clearly measuring the T6-T2 time difference at some level -- maybe<br>
I'm just getting spooked by the log-scale (it highlights the tails on a<br>
gaussian and makes peaks look wider than they should)...<br>
<br>
Hmm. I'd like to understand where all that structure is coming from<br>
though. What run are you looking at?<br>
<div class="im"><br>
> As for the tracking variable, I thought I had fixed this too. I<br>
> realized this problem when looking at some physics replays for the H2<br>
> elastic events. To correct it I ended up removing some cuts from the<br>
> .cdef file. But the cdef file that I am using now is empty. And when<br>
> looking at the H2 elastic events that I replayed yesterday on my<br>
> current d2 set up I get more one-track than 0-track events. Where as<br>
> when I replay a 4-pass 3He and a 5-pass N2 run I get more 0-track<br>
> events. These can be seen here:<br>
</div>[ . . . ]<br>
<br>
Diana, could you replay this run (Matt will tell which one) and see if<br>
you get the same numbers?<br>
<div class="im"><br>
> Any suggestions on what may be causing this? Could the mwdc be too<br>
> tailored to the transversity settings?<br>
<br>
</div>I don't think it should be too bad -- the optics didn't change that much<br>
(as indicated by Xin and Diana's plots from some time back). There's<br>
some distortion at the edges of the acceptance that we can fine tune<br>
out, but it wasn't horrible...<br>
<br>
Are the plots you showed for T2, T6, or all triggers?<br>
<br>
IIRC, 50% no-track events for BigBite T6 triggers might be about right.<br>
There are a lot of gammas that fire the shower, but don't leave tracks.<br>
<br>
T2 triggers involve the Cherenkov (and so require a charged particle).<br>
There should be a much lower fraction of no-track events for that<br>
trigger type.<br>
<br>
The time-zeros for the chambers would have changed between transversity<br>
and d2n though (since the trigger changed). That is one of the<br>
calibration constants in the DB files. If those are only 'close' then<br>
subsequent cuts in the tracking code might throw out the bulk of the<br>
events. The remainder (ie. tail of the peak) would still give a good<br>
track and reasonable reconstructed momentum though. It would be good if<br>
you and Diana double checked those coefficients.<br>
<div><div></div><div class="h5"><br>
-- Brad<br>
<br>
--<br>
Brad Sawatzky, PhD <<a href="mailto:brads@jlab.org">brads@jlab.org</a>> -<>- Jefferson Lab / Hall C / C111<br>
Ph: 757-269-5947 -<>- Fax: 757-269-5235<br>
The most exciting phrase to hear in science, the one that heralds new<br>
discoveries, is not "Eureka!" but "That's funny..." -- Isaac Asimov<br>
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</div></div></blockquote></div><br><br clear="all"><br>-- <br>Matthew Posik<br>Email: <a href="mailto:posik@temple.edu">posik@temple.edu</a><br>Temple University Physics Dept.<br>Office: BA-319<br>Office #: 215-204-1331 <br>
WebSites:<br>Temple:<br><a href="http://quarks.temple.edu/">http://quarks.temple.edu/</a><br>d2n:<br><a href="http://hallaweb.jlab.org/experiment/E06-014/">http://hallaweb.jlab.org/experiment/E06-014/</a><br><br>