[d2n-analysis-talk] T2 timing corrections

Mon Mar 29 12:17:50 EDT 2010

 Hi Brad,

    I think my code is plotting the correct thing, I think I am just poorly
explaining what I am doing, so let me try this again. So I get the value of
Ndata.DBB.t2 from the replayed TTree, in the case of run 2060 Ndata.DBB.t2 =
2.
   Then to plot the T2 trigger, for each event I loop over the hits this is
done using the following for loop:

       for (Int_t hit =0; hit<Ndata.DBB.t2 ; hit++)
         {
             t2_histogram->Fill( DBB.t2[hit] );

         }

    So is this same thing as DBB.t2[Ndata.DBB.t2-1] , since I have T2[ ]
running from 0 to Ndata.DBB.t2-1, ie( T2[0] and T2[1] ) ?

  I also looked at the shoulder events in TDC 04 from run 2060 (
http://jlab.org/~posik/d2n/BB/trigger/t2_walk/2060_tdc04.png )

 I plotted the re-timed TDC 04 (Red histo) and the not retimed TDC 04 (blue
histo) on the same plot in log scale. To make these plots I used the
following cut on each TDC:

                  "BB.tr.n==1&&(DBB.evtypebits&1<<2)==(1<<2)"

I then redid the same plot as above, however this time I did not use the
BB.tr.n==1 cut So the cut on each TDC is now

                    "(DBB.evtypebits&1<<2)==(1<<2)"

You can now clearly see a well defined shoulder in both the re-timed TDC 04
(Red histo) and the not re-timed TDC 04 (blue histo). The plot is here:

http://jlab.org/~posik/d2n/BB/trigger/t2_walk/2060_tdc4_1.png

So it seems that the one track cut greatly reduces this shoulder, but that
may just be because that cut right now is throwing out a lot of statistics.
I also compared the TDC 04 vs the T2 trigger to the re-timed TDC 04 vs the
T2 trigger, this can be seen here:

http://jlab.org/~posik/d2n/BB/trigger/t2_walk/2060_tdc4_t2.png

The re-timed TDC looks good against the T2 trigger (right plot), except
there seems to be a few events that fall at the two horizontal bands at
DBB.t2 = 560 and DBB.t2 = 565 that do not fall in line with the vertical
peak at TDC channel ~260. It is these events that contribute to the shoulder
events in the TDC histogram. I did verify this by plotting the re- timed TDC
04 and making a cut on the T2 trigger, this can be seen here:

http://jlab.org/~posik/d2n/BB/trigger/t2_walk/2060_tdc04_t2_shoulder_ct.png

With that said, I still do not know why these events do not seem to shift
with the T2 re-timing of the TDC. Could they some how be correlated with the
T1, since the T2 trigger is formed from the shower and cerenkov and the
shower had two triggeres, the T1 and T6?

Also I wanted to check where the structure in the T2 at chan. < 400 were
falling in the TDC.

http://jlab.org/~posik/d2n/BB/trigger/t2_walk/2060_tdc4_t2selection.png

 So I plotted for run 2060 the re-timed TDC 04 with T2<400 (red histo,
scaled to the blue histo) and the re-timed TDC 04 with T2>400 (blue histo).
From this is seems that what ever is generating the T2  trigger as chans<400
are events that do not fall into the timing peak of the TDC.

 I am going to take a look at the trigger diagram and see if I can figure
anything out.

-matt

On Fri, Mar 26, 2010 at 6:01 PM, Brad Sawatzky <brads at jlab.org> wrote:

> On Fri, 26 Mar 2010, MATTHEW R POSIK wrote:
>
> > plots that I refer to can be found here:
> >
> > http://jlab.org/~posik/d2n/BB/trigger/t2_walk/<http://jlab.org/%7Eposik/d2n/BB/trigger/t2_walk/>
> <http://jlab.org/%7Eposik/d2n/BB/trigger/t2_walk/>
> >
> > So I took a look at the T2 hits for run 2060 (t2_hits_2060.ps) this
> > shows the hits that the DBB.t2 trigger received. I then plotted DBB.t2
> > making cuts on the hits (t2_2060.ps). In t2_2060.ps the upper left is
> > a plot of DBB.t2 with no cuts, the upper right is DBB.t2 with
> > Ndata.DBB.t2==1 and the bottom plot is Ndata.DBB.t2==2.  It seems that
> > the stuff <500 shows up in the 1st hit data and there is none present
> > in the second hit data.
>
> Recall that the first hit in time is
>  DBB.t2[Ndata.DB.t2 - 1] for Ndata.DB.t2 >= 1
> so, you're not plotting what you intended to plot.
>
> > Also listed here is cor_tdc_2060.ps, which is a plot of the retimed T2
> > TDCs.  Originally I thought that the plateau to the right of the main
> > peak was due to the TDCs being timed off the T6 trigger, but even with
> > retiming the TDCs off the T2 trigger, some still have this plateau to
> > the right of the main peak.
>
> Make sure you haven't made an error in your code.  Your previous plots
> showed a very clear correlation between those shoulder events and T6
> carrying the L1A timing.  These plots look like they are missing the
> correction.  Plot the corrected and uncorrected TDC histos (log scale)
> on the same plot (ie. one in red, one in blue) so the effect of the
> timing correction is clearly visible.
>
> > I also plotted the T2 trigger and made cuts on it to various BigBite
> > Cerenkov pmts by cutting on ADCs. For example T2_adc_cut.png, I
> [ . . . ]
> > I was hoping to see the peaks at chan >500 change with each ADC cut,
> > but looking at it, they look pretty similar regardless of the PMT that
> > is selected.
>
> Weird.  That structure *has* to correlate to something -- either a
> trigger type and/or some detector component(s) that make up the
> trigger...
>
> If the spike at ~560 is the self-timing peak for when T2 generates the
> L1A, and later times are at smaller bins (common stop TDC), then what
> the heck is causing the gap from 460--280?  That gap starts 50ns after
> the the trigger and ends 150ns after the trigger -- that's not physics,
> that's electronics.  Take a look at the trigger diagram on the wiki and
> see if you can work out what's going on.  I'll try to look at it myself
> before our next meeting, remind me then if it doesn't make sense...
>
> -- Brad
>
> --
> Brad Sawatzky, PhD <brads at jlab.org>  -<>-  Jefferson Lab / Hall C / C111
> Ph: 757-269-5947  -<>-  Fax: 757-269-5235  -<>- Pager: brads-page at jlab.org
> The most exciting phrase to hear in science, the one that heralds new
>  discoveries, is not "Eureka!" but "That's funny..."   -- Isaac Asimov
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-- 
Matthew Posik
Email: posik at temple.edu
Temple University Physics Dept.
Office: BA-319
Office #:  215-204-1331
WebSites:
Temple:
http://quarks.temple.edu/
d2n:
http://hallaweb.jlab.org/experiment/E06-014/
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