In previous A_LL papers for jets and neutral pions, we have included figures demonstrating the range of x1,x2 for the
pdfs sampled by the kinematic cuts on our data. 

I thought I would generate such a figure for the FMS A_LL paper.
I used PYTHIA8.205  with the CTEQ5L pdfs set.  I have not adjusted the tune
to be other than the default that comes with the PYTHIA8 download.

I made the following cuts on the final pions:

pT> 2 GeV/c
E > 20 GeV
2.5<eta<4.0
x1<x2
All pions in the event are plotted.  No trigger requirements.

I have included a few more correlation plots to demonstrate that unlike at central rapidity, we don't see a
clear correlation with pT, E, or eta and x1,x2.