Hi Dave,<br><br> I talked to Chiranjib about the beta cut for the electrons identification. <br> He said that there is no need to apply such cut to select the electrons <br> sample since the time resolution of the S1 plane is two times worse <br>
than the S2m plane. <br><br> In his analysis, he used the RF timing to calibrate the S2m plane. <br> The obtained resolution was ~ 500 ps. But the time resolution of S1 <br> plane was ~ 1ns, which is not so good to be required for any particle's <br>
identification.<br><br> In fact, I don't know what is the reason behind your beta cut requirement. <br> A good electrons sample can be selected by combining the Cerenkov <br> and the pion rejector signals. Of course the timing information is implicitly <br>
included to extrapolate the track from the vertex; the interaction point in the <br> target plane, through different LHRS detectors. For that reason an adequate <br> scintillators calibration is necessary to extract the particle's time of flight. <br>
<br> As for your beta distribution plot, I can't understand why the main peak is <br> not centered around 1. This shift can be related to the time calibration of the <br> scintillators planes. Have you done this calibration or not yet?<br>
<br> Best regards,<br><br><div class="gmail_quote"><div> Lamiaa<br><br> PS: Since I forgot to change my gmail address to the JLab one, I got a notification <br> email that my message is waiting for the moderator approval. So, I canceled the last <br>
posting to this mailing list. I apologize for the people who my receive this email twice.<br> <br></div><blockquote class="gmail_quote">
<font color="#888888"><br></font><div class="gmail_quote"><div><div></div><div class="h5">On Wed, Oct 28, 2009 at 12:26 PM, David Flay <<a href="mailto:flay@jlab.org">flay@jlab.org</a>> wrote:<br>
</div></div><blockquote class="gmail_quote"><div><div></div><div class="h5">
Hey Brad,<br>
<br>
To follow up from last meeting our discussion about the effect of a cut on<br>
either the Cerenkov ADC or beta as seen in the Cerenkov Detector plane,<br>
I've assembled some plots.<br>
<br>
The first is the the detector plane (L.cer.trx:L.cer.try) with some<br>
'standard cuts' (= evtypebits cut for T3, one-track, VDC).<br>
<br>
The second is the standard ones plus a cut on the Cerenkov sum (greater<br>
than 600 channels) -- no change in the distribution; so that wasn't the<br>
issue.<br>
<br>
The third is the previous two cuts, plus a cut on the main peak of beta<br>
(see last plot for a plot of beta) -- there's a preference for the events<br>
to fill the lower portion of the plot here. Considering that beta is<br>
constructed based off the timing between the S1 and S2 planes, maybe the<br>
underlying issue is in the Scintillators?<br>
<br>
<br>
<br>
-------------------------------------------------<br>
David Flay<br>
Physics Department<br>
Temple University<br>
Philadelphia, PA 19122<br>
<br>
office: Barton Hall, BA319<br>
phone: (215) 204-1331<br>
<br>
e-mail: <a href="mailto:flay@jlab.org">flay@jlab.org</a><br>
<a href="mailto:david.flay@temple.edu">david.flay@temple.edu</a><br>
<br>
website: <a href="http://www.jlab.org/%7Eflay">http://www.jlab.org/~flay</a><br>
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