[d2n-analysis-talk] T2 timing corrections

[posik at jlab.org]

Hi Brad,

  So I have been looking at this T2 timing corrections. All plots are from
run 2060 and can be found here:

http://jlab.org/~posik/d2n/BB/trigger/t2_walk/t6_timing/trig_evo/

 The first plot 2060_t2.png shows the T2 structure on linear scale. Since
there are more than one peak in this structure I decided to use different
peaks as the T2 self timing peak and see how that affects the retiming.

So the second plot (t2_correction_evo.png) shows the zeroth hit of TDC 04
with the T2 retiming and is plotted as follows from left to right:

(Top) TDC 04 no correction, T2 correction using self timing peak of 194,
T2 correction using self timing peak of 252

(bottom) T2 correction using self timing peak of 500, T2 correction using
self timing peak of 530, T2 correction using self timing peak of 555

The next plot (t2vstdc.png) shows t2[0](y-axis):TDC04[0](x-axis) for
various self timing peaks and follows the same layout as the plot above.

Finally I looked at DBB.t2 with the various DBB.evtypebits&1<<x)==(1<<x)
cuts applied to it, where x = 1,2,6,7,8 corresponding to the BigBite
triggers. This is plotted in (trigger_cuts_evo.png) and arranged as
follows:

(Top) T2 no evtypebit cuts, T2 with evtypebit 1 cut, T2 with evtypebit 2 cut

(Bottom) T2 with evtypebit 6 cut, T2 with evtypebit 7 cut, T2 with
evtypebit 8 cut

It seems that the T2 retiming improves the Cerenkov TDCs no matter what
self timing peak I select. This can be seen in the 2nd and 3rd plots. I am
not sure how to go about and begin to determine which of the peaks I
should use. Any suggestions on where I may start to look?

In the evtypebit cuts on the last plot, when I cut on
(DBB.evtypebits&1<<7)==(1<<7) I end up with no events. I am guessing that
this is do to the large prescale, which was at 65535?

Thanks
Matt