[d2n-analysis-talk] Positron Vertex Histogram Question

[Gregg B. Franklin]

Matt,
   I've been re-reading some of the info you provided on the positron 
data.  In your talk of 4/21/2011, you have comparisons of distributions 
from standard BigBite running and reverse-polarity running.  The 
distributions are generally very similar.  The z-vertex distribution 
(your slide 12) is particularly interesting since I would expect the 
z-vertex distribution for positrons to be very different from 
elecxtronce since (I think) the tracks should point back to gamma 
conversion points.

   I assume your plot is for all good positive tracks.  Am I right? 
Would it be possible to see what this same distribution would look like 
if all the "good electron" cuts (like Cerenkov, preshower, E/p...) were 
applied also?  I'm thinking that the positrons might come from the 
collimators that shield BigBite from the ends of target.  If this is 
true, the z-vertex distribution for positrons should be greatly enhanced 
at z=+/- 0.2 m.  AND if this is true, we could cut at least some of them 
out.

   Would it be possible to produce the z-vertex plot for positrons only? 
  (If slide 12 already has these cuts, then I'm really confused on why 
it looks just like the normal-polarity running.)

Regards,
Gregg



-- 
Prof. Gregg B Franklin
Head, Department of Physics
Carnegie Mellon University
phone: (412) 268-2743   fax: (412) 681-0648