[d2n-analysis-talk] inelastic events and misc. events in BigBite

[Matthew R. Posik]

On Mon, Oct 24, 2011 at 12:19 PM, Brad Sawatzky <brads at jlab.org> wrote:

>
> On Sun, 23 Oct 2011, posik at jlab.org wrote:
>
> [ . . . ]
> > I then computed the ratio of inelastic to misc events for 4 runs, and
> then
> > computed the weighted ratio over the 4 runs. I ended up with the ratio of
> >
> > inelastic/misc events =  3.932 +/- 0.065 %
> >
> > Finally, I also took a look at how the misc. events compare to the
> > inelastic events in the BigBite Cerenkov ADCs. This can be seen in the
> > plot Neg_Ration_CerADC.pdf, where I plotted the inelastic events in red
> > and misc events in blue for several ADCs. On the left are ADCs
> > 4(top),5(middle) and 6(bottom). On the right are ADCs 14(top), 15(middle)
> > and 16(bottom). Looking at the Cerenkov ADCs, we can see that the misc
> > events fall right around the mean value of the inelastic events.
>
> I just want to correct myself again. I had a typo in my original email. I
originally said the the ratio of inelastic/misc events was 3.9%, However I
meant to say the ratio of misc/inelastic events is 3.9%


> When I look at the CerADC plots I see the ratio of
>  "inelastic w/ cherenkov signal" : "misc events w/ cherenkov signal"
> seems to be 40:1 vs. the 3.9:1 ratio seen in the shower.
>
> Is there a missing prescale factor or something, or does that tell us
> that something like 90% of the misc events are missing signal in the
> Cherenkov ADC?


When computing the ratio of misc/inelastic events, I would need to correct
for charge,pre-scale and livetime. However, I computed a ratio for each run,
and then computed  the weighted average of all the  ratios from each run. By
doing this the pre-scale,livetime and charge corrections cancel out. When I
showed the plots of some Cerenkov ADCs, I simply added all the events from
the 4 runs together using

chain->AddFile(run 1)
 chain->AddFile( run 2)... ect

So in this way I did not correct for live time, charge or prescale factors.
However I did recalculate the ratio correcting for charge, livetime and
prescale, and the ratio still was 3.9%.

 When I did the ratio seen in the shower, I applied the cut that said if the
event triggered any of the 20 TDCs in the correct timing range and the event
also passed through the location correlated with the Cer TDC (Cer mirror
cut) that fired then it is a good event. So the cut looks something like

   (TDC01 && Mir01) | | (TDC02 && Mir02) | | ...(TDC20 && Mir20).

 When plotting the Cerenkov ADCs, I used a slightly different cut. In those
plots I showed rather than using the cut that allows any of the TDCs to
fire, I used the cut that allows the event to pass only if the event fires
the TDC and passes through the mirror location of the pmt I am looking at.
So for example when I plotted ADC 04 I had the Cer cut
    TDC04 && Mir04
 And when I plotted ADC 14 I used the cut
     TDC14 && Mir14

In the Cerenkov ADC plots, I only showed 6 of the 20 ADCs that we have.
Looking at where the misc. events land in the shower, I would imagine that
the misc signals in ADCs 1,2,11 and 12 would be larger, then the ADCs near
the physical bottom of the detector. I will take a look at this later
today.

So when looking at misc/inelastic in the shower the ratio is 3.9% and when
looking at the Cerenkov signal of misc/inelastic which is 1/40 = 2.5%, they
do not seem too far apart.

 You mention that production cuts are in place for these
> plots (with the noted exceptions).  I presume the Cherenkov ADC/TDC cuts
> must also be disabled since I don't see evidence of the cut in the Cer
> ADC spectra?  (Or is the cherenkov _sum_ still always over 400ch and
> these plots are just showing ~1 pe backgrounds?)
>

I have applied cuts to the Cerenkov TDCs and matched the track to the
position of the Cerenkov mirrors. There are no Cerenkov ADC cuts applied.
The Cerenkov TDC and mirror cuts get rid of most of the 1 pe background
which would fall near ADC ch 50 or so. I have attached a plot where I plot
the ADCs with same cut I described in the first email, but for the misc
events(blue histo.) I have removed the TDC and mirror cut so you can see the
1 pe background.

-Matt








>
> -- 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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