[d2n-analysis-talk] APS talk (Cerenkov pedestals)

[Brad Sawatzky]

On Tue, 09 Feb 2010, MATTHEW R POSIK wrote:

[ . . . ]
> For the red histo I then apply a TDC and mirror cut that apply to
> mirror 13.  Where as for the blue histo I apply to mirror 13(ie. ADC
> 13 ) a cut on the TDC and mirror associated with mirror 17.
> 
> But if I replay the first 100,000 with a T8 cut
> ("DBB.evtypebits&1<<8)==1<<8") the peds I get for both sides are below
> (1849_beam.png and 1849_rhrs.png) for the beam line and rhrs sides.

The center of the pedestal for Mirror 3 from the T8 cut is consistent
with the rough centroid of the blue background shown in
aps_mir3_no_cor.png.  That makes sense.

> Since when I make that "background" cut (blue histo) on mirror 13 and
> have a non zero centered peak, does that mean there is some
> correlation between mirror 13 and 17?

I'd double check that the pedestal you're subtracting is really the one
you're showing in 1849_rhrs.png -- I'll bet it isn't.  (I should be able
to see the pedestal start to rise up in the lowest bins of your mirror13
ped-subracted plot in your talk, but there's nothing there.)

That is, make the same kind of non-ped-subtracted plot for mirror 13 as
you did for aps_mir3_no_cor.png.  If there really is a pedestal below
the blue peak, we should see it.

-- 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