[d2n-analysis-talk] Pions from run 1530 where pre-shower sum was not included in trigger

[Vahe Mamyan]

Hi Diana,

> Do we know this is true? (That is, that the total energy is around 0.6
> GeV?) The momentum cut is on the track reconstruction in the wire
> chambers, not on the total energy deposit in the calorimeter. There
> are lots of events where the momentum is different from the total
> energy deposit, and that's a major piece of the pion rejection.

Yes, it is true. Plotting sum of pre-shower shower energy peaks gives
6.22474e-01 +- 7.59145e-02 GeV, which is expected from total shower
resolution.
For the qualitative analysis there is probably no need to use all strict
cuts applied in
real analysis: the pion ionization peak is so huge that events are mostly
pions, any other background is
not that important. I am not trying to estimate number of electron to pion
ratio.
I just wanted to show that pions that give ionization in pre-shower and
trigger the total shower
distort the energy deposition shape in the shower ( symmetric shape is
expected from electrons) ,
giving a peak near 0.55 GeV for tracks that that have BB.tr.p = 0.6 +0.1
GeV.

Best regards,
Vahe




On Fri, Dec 2, 2011 at 12:55 PM, Diana Parno <dparno at uw.edu> wrote:

> > ... the blue peak corresponds to pions that have a sharp red peak
> > in pre-shower to give total energy around 0.6 GeV ...
>
> > ... momentum cut abs(BB.tr.p-0.6)<0.1 takes only
> > pions that deposit more than 0.1 GeV energy in pre-shower.
>
> Do we know this is true? (That is, that the total energy is around 0.6
> GeV?) The momentum cut is on the track reconstruction in the wire
> chambers, not on the total energy deposit in the calorimeter. There
> are lots of events where the momentum is different from the total
> energy deposit, and that's a major piece of the pion rejection.
>
> Also, any time that you want to look at tracking variables (momentum,
> angle, etc), it is really important to impose the basic optics
> validity cuts so that you can trust the numbers coming out of the
> tracks. Momentum reconstruction, front-track reconstruction, etc, are
> not calibrated for some regions of the magnet. I strongly suggest that
> you add the cuts mag && projx to your basic toolkit here. (Those are
> the names they have in my macro. The actual cuts are defined thus:
>        TCut mag = "BB.optics.vzflag[]==1 && BB.tr.tg_th[]<0.2";
>        TCut projx = "(BB.optics.bendx + 0.23*BB.tr.ph)>-0.097 &&
> (BB.optics.bendx + 0.23*BB.tr.ph)<0.13"; )
> The mag cut excludes the uncalibrated regions of the magnet
> acceptance. The projx cut excludes a certain part of the acceptance
> where we think that rescattering has taken place.
>
> There are also a lot of accidentals to consider, i.e. situations where
> the reconstructed track does not line up with the location of the
> preshower or shower hit. The trps and trsh cuts are supposed to impose
> alignment between the two systems. The basic_qual cut in my macro
> combines a number of these data-quality cuts. If you're looking at a
> replayed root file, you can modify it so that it doesn't include the
> skim.* variables, which are present only in the skimmed root files.
>
> Best,
> Diana
>
> On Dec 2, 2011, at 6:44 AM, Vahe Mamyan wrote:
>
> >  Hello,
> >
> > In  run 1530 pre-shower sum was not included in trigger and pions
> > are plenty.
> > Attached is pre-shower and shower energy distribution with  Cerenkov
> > cut Diana had in her macro.
> > TCut = cer_cut = basic_e&&cer_tot&&"abs(BB.tr.p-0.6)<0.1";
> >
> > Since I applied a cut on BB.tr.p to be around 0.6 GeV the blue peak
> > corresponds to pions that have a sharp red peak
> > in pre-shower to give total energy around 0.6 GeV. As you can see if
> > one removes the pion peak from shower energy
> > distribution the remaining spectrum in shower looks symmetric and in
> > pre-shower too.
> > Also it can be seen that the blue pion peak is centred at around 0.5
> > GeV and looking at
> > https://hallaweb.jlab.org/wiki/images/e/e0/Bbsimulation_new.pdf page
> > 2 left blue spectrum one can see that there is similar peak in
> > around 0.5 GeV.
> > The peak in page 2 is not as visible as in run 1530 because pre-
> > shower sum was included in the trigger and momentum cut
> > abs(BB.tr.p-0.6)<0.1 takes only
> > pions that deposit more than 0.1 GeV energy in pre-shower.
> >
> > I still think that Cerenkov adc cut was not enough to remove much
> > pions as Mattew showed in page 11 of his report.
> > I estimated Cerenkov rejection power to be 1:5.5 from run 1530.
> > According to Wiser parametrization there are about 24 pions for each
> > electron in BigBite acceptance, so roughly
> > there are  4.3 pions for each electron and taking account that most
> > pions are at lower energy, this number is higher.
> >
> > Best regards,
> > Vahe
> > <pre-
> > shower_shower_energy
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