[Halla_pi0] pi0 meeting

[richard lindgren]

Hi,

There is still something that doesn't look right about Coles plots for D1 kinematics at low W. I agree with your comments about the cone fitting into BigBite and if you don't have the cone, then you won't see anything.

  However, it appears to me that you do have the cone. If you look at the plot of thee ellipses which I have attached, you will see that -54 degrees BitBite 2 setting contains half of the cone at low Q2 and low W . In fact it is centered at W=3.77 MeV and Q^2 =0.058, but when you look at the plots for D1 kinematics which is -54 degrees, you do not see much of a missing mass peak until about 5.5 MeV. Below 5.5 MeV there is no missing mass peak and you should see something.

If you make the same comparison with BigBite 3 kinematics which is -43.5 degrees (The ellipse plot shows it for -42 degrees), you see a beautiful missing mass peak all the way down to threshold. BigBite is centered at about 1.687 MeV. The position of BigBite 3 and BigBite 2 are basically similar in terms of proton momentum except one is on the right side of the ellipse, which  is phi=0 deg pion cm, and one is on the left side, which is phi=180 degree pion cm angle.  How can the missing mass peak be so clear on one side all the way down to threshold and not even visible on the other side. It is not kinematics or the cone because in both case at least half of the cone is in BigBite based on the ellipse figure.

Please take a look at this. 

Richard

Dr. Richard A Lindgren
Research Professor of Physics
Department of Physics
University of Virginia
382 McCormick Rd
Charlottesville, VA 22904
ral5q at virginia.edu







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