[d2n-analysis-talk] Scintillator Timewalk

[Brad Sawatzky]

Hi David,

These emails should really be going to the -talk mailing list.  Among
other things it gives us an archive of this discussion for future
reference.

On Mon, 01 Mar 2010, David Flay wrote:

> Attached are the TDC vs ADC (corrected variables) for each paddle in
> S2m.  There doesn't seem to be a double peak structure in the TDC for
> a given ADC, along with the events falling at a fairly consistent
> value in the TDC.
> 
> There are a few plots (#6,7) that seem to have an extra peak, above
> the main one... even if it is not as prominent -- though I may just be
> 'looking for it' so to speak.

The TDC structure is a little puzzling. I see a primary peak at a TDC
value of 0.060 and a second peak at 0.070--0.080 in most of the
histograms.  The binning is pretty coarse though, so it's a little
ambiguous...

Could you replot with finer binning along the tdc axis?  Place a cut on
single tracks, T3 triggers only (no edtm, no T4, etc), and find out what
the units are on the TDC axis.  It would be nice to know if the two
peaks are ~10ns apart, or 10ps apart...  If it's ps then it is either a
bug or a binning artifact.

> Overall, it seems these corrected values don't show a prominent
> timewalk effect, from what I can tell.

The timewalk correction seems to be complete at some level (the main
peak is nice and flat).  I don't know what to think about outliers at
larger TDC values though...

-- Brad

-- 
Brad Sawatzky, PhD <brads at jlab.org>  -<>-  Jefferson Lab / Hall C / C111
  Ph: 757-269-5947 -<>- Pager: 757-584-5947 -<>- Fax: 757-269-7848
The most exciting phrase to hear in science, the one that heralds new
  discoveries, is not "Eureka!" but "That's funny..."   -- Isaac Asimov