Hi Gregg,<div><br></div><div> here is a plot of the z vertex with the BigBite magnet running in positive polarity. I applied all of the cut we have been using for the electrons to this plot, ie projected track to calorimeter positions, cerenkov cuts, pre-shower ect. The only cut I changed a little was the E/p, the low end of that cut for electrons was 0.833 and I lowered it to 0.763 for positive polarity. </div>
<div><br></div><div>-Matt<br><br><div class="gmail_quote">On Tue, May 3, 2011 at 8:30 PM, Gregg B. Franklin <<a href="mailto:gbfranklin@cmu.edu">gbfranklin@cmu.edu</a>> wrote:<br><blockquote class="gmail_quote">
Matt,<br>
I've been re-reading some of the info you provided on the positron<br>
data. In your talk of 4/21/2011, you have comparisons of distributions<br>
from standard BigBite running and reverse-polarity running. The<br>
distributions are generally very similar. The z-vertex distribution<br>
(your slide 12) is particularly interesting since I would expect the<br>
z-vertex distribution for positrons to be very different from<br>
elecxtronce since (I think) the tracks should point back to gamma<br>
conversion points.<br>
<br>
I assume your plot is for all good positive tracks. Am I right?<br>
Would it be possible to see what this same distribution would look like<br>
if all the "good electron" cuts (like Cerenkov, preshower, E/p...) were<br>
applied also? I'm thinking that the positrons might come from the<br>
collimators that shield BigBite from the ends of target. If this is<br>
true, the z-vertex distribution for positrons should be greatly enhanced<br>
at z=+/- 0.2 m. AND if this is true, we could cut at least some of them<br>
out.<br>
<br>
Would it be possible to produce the z-vertex plot for positrons only?<br>
(If slide 12 already has these cuts, then I'm really confused on why<br>
it looks just like the normal-polarity running.)<br>
<br>
Regards,<br>
Gregg<br>
<br>
<br>
<br>
--<br>
Prof. Gregg B Franklin<br>
Head, Department of Physics<br>
Carnegie Mellon University<br>
phone: (412) 268-2743 fax: (412) 681-0648<br>
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</blockquote></div><br><br clear="all"><br>-- <br>Matthew Posik<br>Email: <a href="mailto:posik@temple.edu">posik@temple.edu</a><br>Temple University Physics Dept.<br>Office: BA-319<br>Office #: 215-204-1331 <br>WebSites:<br>
Temple:<br><a href="http://quarks.temple.edu/">http://quarks.temple.edu/</a><br>d2n:<br><a href="http://hallaweb.jlab.org/experiment/E06-014/">http://hallaweb.jlab.org/experiment/E06-014/</a><br><br>
</div>