Hi Diana,<br><br><span style="color: rgb(255, 0, 0);">> Do we know this is true? (That is, that the total energy is around 0.6</span><br style="color: rgb(255, 0, 0);"><span style="color: rgb(255, 0, 0);">> GeV?) The momentum cut is on the track reconstruction in the wire</span><br style="color: rgb(255, 0, 0);">
<span style="color: rgb(255, 0, 0);">
> chambers, not on the total energy deposit in the calorimeter. There</span><br style="color: rgb(255, 0, 0);"><span style="color: rgb(255, 0, 0);">
> are lots of events where the momentum is different from the total</span><br style="color: rgb(255, 0, 0);"><span style="color: rgb(255, 0, 0);">
> energy deposit, and that's a major piece of the pion rejection.</span><br style="color: rgb(255, 0, 0);"><br>Yes, it is true. Plotting sum of pre-shower shower energy peaks gives <br>6.22474e-01 +- 7.59145e-02 GeV, which is expected from total shower resolution. <br>
For the qualitative analysis there is probably no need to use all strict cuts applied in <br>real analysis: the pion ionization peak is so huge that events are mostly pions, any other background is <br>not that important. I am not trying to estimate number of electron to pion ratio. <br>
I just wanted to show that pions that give ionization in pre-shower and trigger the total shower <br>distort the energy deposition shape in the shower ( symmetric shape is expected from electrons) , <br>giving a peak near 0.55 GeV for tracks that that have BB.tr.p = 0.6 +0.1 GeV. <br>
<br>Best regards,<br>Vahe<br><br><br><br><br><div class="gmail_quote">On Fri, Dec 2, 2011 at 12:55 PM, Diana Parno <span dir="ltr"><<a href="mailto:dparno@uw.edu">dparno@uw.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
> ... the blue peak corresponds to pions that have a sharp red peak<br>
> in pre-shower to give total energy around 0.6 GeV ...<br>
<br>
> ... momentum cut abs(BB.tr.p-0.6)<0.1 takes only<br>
<div class="im">> pions that deposit more than 0.1 GeV energy in pre-shower.<br>
<br>
</div>Do we know this is true? (That is, that the total energy is around 0.6<br>
GeV?) The momentum cut is on the track reconstruction in the wire<br>
chambers, not on the total energy deposit in the calorimeter. There<br>
are lots of events where the momentum is different from the total<br>
energy deposit, and that's a major piece of the pion rejection.<br>
<br>
Also, any time that you want to look at tracking variables (momentum,<br>
angle, etc), it is really important to impose the basic optics<br>
validity cuts so that you can trust the numbers coming out of the<br>
tracks. Momentum reconstruction, front-track reconstruction, etc, are<br>
not calibrated for some regions of the magnet. I strongly suggest that<br>
you add the cuts mag && projx to your basic toolkit here. (Those are<br>
the names they have in my macro. The actual cuts are defined thus:<br>
TCut mag = "BB.optics.vzflag[]==1 && BB.tr.tg_th[]<0.2";<br>
TCut projx = "(BB.optics.bendx + 0.23*<a href="http://BB.tr.ph" target="_blank">BB.tr.ph</a>)>-0.097 &&<br>
(BB.optics.bendx + 0.23*<a href="http://BB.tr.ph" target="_blank">BB.tr.ph</a>)<0.13"; )<br>
The mag cut excludes the uncalibrated regions of the magnet<br>
acceptance. The projx cut excludes a certain part of the acceptance<br>
where we think that rescattering has taken place.<br>
<br>
There are also a lot of accidentals to consider, i.e. situations where<br>
the reconstructed track does not line up with the location of the<br>
preshower or shower hit. The trps and trsh cuts are supposed to impose<br>
alignment between the two systems. The basic_qual cut in my macro<br>
combines a number of these data-quality cuts. If you're looking at a<br>
replayed root file, you can modify it so that it doesn't include the<br>
skim.* variables, which are present only in the skimmed root files.<br>
<br>
Best,<br>
Diana<br>
<div><div></div><div class="h5"><br>
On Dec 2, 2011, at 6:44 AM, Vahe Mamyan wrote:<br>
<br>
> Hello,<br>
><br>
> In run 1530 pre-shower sum was not included in trigger and pions<br>
> are plenty.<br>
> Attached is pre-shower and shower energy distribution with Cerenkov<br>
> cut Diana had in her macro.<br>
> TCut = cer_cut = basic_e&&cer_tot&&"abs(BB.tr.p-0.6)<0.1";<br>
><br>
> Since I applied a cut on BB.tr.p to be around 0.6 GeV the blue peak<br>
> corresponds to pions that have a sharp red peak<br>
> in pre-shower to give total energy around 0.6 GeV. As you can see if<br>
> one removes the pion peak from shower energy<br>
> distribution the remaining spectrum in shower looks symmetric and in<br>
> pre-shower too.<br>
> Also it can be seen that the blue pion peak is centred at around 0.5<br>
> GeV and looking at<br>
> <a href="https://hallaweb.jlab.org/wiki/images/e/e0/Bbsimulation_new.pdf" target="_blank">https://hallaweb.jlab.org/wiki/images/e/e0/Bbsimulation_new.pdf</a> page<br>
> 2 left blue spectrum one can see that there is similar peak in<br>
> around 0.5 GeV.<br>
> The peak in page 2 is not as visible as in run 1530 because pre-<br>
> shower sum was included in the trigger and momentum cut<br>
> abs(BB.tr.p-0.6)<0.1 takes only<br>
> pions that deposit more than 0.1 GeV energy in pre-shower.<br>
><br>
> I still think that Cerenkov adc cut was not enough to remove much<br>
> pions as Mattew showed in page 11 of his report.<br>
> I estimated Cerenkov rejection power to be 1:5.5 from run 1530.<br>
> According to Wiser parametrization there are about 24 pions for each<br>
> electron in BigBite acceptance, so roughly<br>
> there are 4.3 pions for each electron and taking account that most<br>
> pions are at lower energy, this number is higher.<br>
><br>
> Best regards,<br>
> Vahe<br>
</div></div>> <pre-<br>
> shower_shower_energy<br>
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