[d2n-analysis-talk] BB cer pion rejection plots

[MATTHEW R POSIK]

Hi Brad,

  I do not understand the large change in the pion rejection from PMT 14,16.
I spent a lot of time last night looking into it, but could not conclude
why. I talked to Dr. Meziani about it and said he needed to think about it.
Do you have any ideas? I should also mention that pmts 11,12 and 18 had no
events left in the pion sample after I applied the Cerenkov cut to them.

The errors that I had on the pion rejection factors were not completely
correct. Since I am plotting N_p/N_e, where N_p is my initial pion sample,
and N_e is the number of events left after my Cerenkov cut, then my error
should be

(1/N_e)*sqrt(N_p)

My most recent version of the talk that I just sent out has this plot with
the errors above on it. The error bars are hidden due to the log scale. But
the ranged on average from 1-20.

For the pion rejection, I used the T6 and the initial pion sample  on the
small angle side ranged from ~5000-3000 events per mirror, with pmt 8 having
400 events. And for the large angle side the initial pion sample ranged from
3000-900 events per mirror, with pmt 18 having 200 events.

Thanks
-Matt

On Tue, Dec 7, 2010 at 9:12 AM, Brad Sawatzky <brads at jlab.org> wrote:

>
> The change in pion rejection for PMTs 14,16 are pretty strange.  Any
> idea why?  I presume the large error bars are due to using T1 or T6
> data?  (Which is fine, I'm just checking.)
>
> -- Brad
>
> On Mon, 06 Dec 2010, posik at jlab.org wrote:
>
> >   So I added some error bars to the BB cerenkov pion rejection factors
> > that I showed last week. I also redid the rejection factor vs BB Cer
> > photo electron cut using the pion selection of E/p<0.8 and 10 <
> > preshower < 250.
> >
> > So the plot pion_selection.eps shows my pion sample selection.
> >
> > I then looked at how many particles from the pion sample were passing
> > through the geometrical location of a Cerenkov mirror, I called this
> > variable N_p. I then how many of the N_p particles also fired the
> Cerenkov
> > ADC and TDC and called this number of events N_e. I then defined my pion
> > rejection factor as
> >
> > pion_rejection = N_p/N_e, and following Dr. Meziani's advice took the
> > Sqrt(N_p) as my error.
> >
> > I did this for each pmt, see cer_pi_rej.eps for the small angle side and
> > rhrs_cer_pi_rej.eps for the large angle side. The different data markers
> > represent the rejection factor at different BB Cerenkov ADC
> photo-electron
> > cuts. I also plotted the average rejection factor for each side of the
> > Cerenkov as a function of photo-electron cut, see cer_avg_pi_rej.eps and
> > rhrs_cer_avg_pi_rej.eps.
> >
> > I am now going to do a similar thing for the electron efficiency.Please
> > let me know what you think of these plots.
>
> --
> 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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