Hi Greg,<br><br><div class="gmail_quote">On Wed, Apr 20, 2011 at 8:56 PM, Gregg B. Franklin <<a href="mailto:gbfranklin@cmu.edu">gbfranklin@cmu.edu</a>> wrote:<br><blockquote class="gmail_quote">
Matt,<br>
The plots you have are very interesting. The dilution factor at low<br>
x is a much bigger effect than we were anticipating. I think we should<br>
first try to make sure we agree on the dilution factor determined by the<br>
reverse polarity run at 4.7 GeV. It would be useful to plot 1-D instead<br>
of D since D gets close to 1.0 through much of our range. Lets make<br>
sure we agree on the runs, the cuts, etc.<br></blockquote><div><br>I plotted 1-D. Again D is defined as:<br><br> D = 1-(Q-/Q+)*(N+/N-), <br><br> Q-, N- is the accumulated charge and total counts from the negative polarity runs 2024-2195<br>
<br> Q+, N+ is the accumulated charge and total counts from the positive polarity runs 2199-2212<br><br>The plot pos_outrun_1mdilution.eps shows 1-D. Since the higher x bins are near 0 here I also plotted it on log scale (pos_outrun_1mdilution_log.eps)<br>
<br>I also plotted 1-D' for the negative polarity runs 2024-2195 using BB.optics.charge==-1 for electrons and BB.optics.charge==1 for positrons<br><br>Again here D' is defined as<br> <br> D' = 1 - N-/N+<br><br>
where N- are the total counts with charge==-1 <br> N+ are the total counts with charge==1<br><br>You can see a plot of 1-D' pos_inrun_1mdilution.eps <br></div><blockquote class="gmail_quote">
<br>
We also want to check the asymmetry, also. If it is large, this is a<br>
big problem in addition to just "dilution factor". We need to at least<br>
put a bound on the asymmetry.<br></blockquote><div><br>I Computed the raw positron asymmetry from the positive polarity runs. I will send that result out in a separate email. <br></div><blockquote class="gmail_quote">
<br>
For the 5-pass data, the following strategy might work if we have<br>
enough statistics.<br>
<br>
1) Start with the 4.7 GeV data and determine the positrons (from reverse<br>
polarity running) normalize by charge as a 2-D function of momentum and<br>
scattering angle. Call this 2D histogram 1. It will have to be course<br>
binned.<br>
<br>
2) Do the same for positrons determined from the negative (normal<br>
polarity) running at 4.7G. In both cases, we should have mostly just<br>
positrons. Call this histogram 2.<br></blockquote><div><br>I will get started on getting these histograms. <br></div><blockquote class="gmail_quote">
<br>
3) Determine the ratio of Hisogram 2) over Histogram 1) bin by bin<br>
should give use the relative acceptance for positrons as a function of<br>
scattering angle and momentum. (Our statistics will be poor at high x,<br>
but hopefully the positrons aren't a problem there.)<br>
<br></blockquote><div>I don't think positrons will be an issue here, looking at the dilution factors that I got using the two different methods, they seem to both agree pretty well at large x and both say very few positrons at large x.<br>
<br></div><blockquote class="gmail_quote">
3) For the 5-pass data, make hisogram 3 with similar bins for positrons.<br>
This will be for the normal polarity, which means the acceptance will<br>
be very different than for the real data. However, you can use the<br>
ratios (bin by bin) determined in step 3 to correct for this. The<br>
problem might be that the "4-pass" data may have low statistics in<br>
kinematics bins that become important at 5-pass.<br>
<br>
In the longer run, we can try to understand this ratio with Monte Carlo.<br>
If there is a large asymmetry and therefore can depend on the target<br>
polarization direction, it will be harder.<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>
_______________________________________________<br>
d2n-analysis-talk mailing list<br>
<a href="mailto:d2n-analysis-talk@jlab.org">d2n-analysis-talk@jlab.org</a><br>
<a href="https://mailman.jlab.org/mailman/listinfo/d2n-analysis-talk">https://mailman.jlab.org/mailman/listinfo/d2n-analysis-talk</a><br>
</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>