[Halla_pi0] pi0 meeting

[richard lindgren]

Greetings,

I thought I sent this out around Noon today, but maybe not since I do not see my email about it.

Cole, Khem and I talked for about 1 1/2 hours.

We mostly reviewed where we stood on past corrections and problems. For example,

1) Recall there was the trigger threshold problem when the trigger switched from the 3 mm scint. to the 30 mm scint. 
   This was traced to the AND between the left and right end PMTs and we were losing triggers from low energy protons that did not make sufficient light to travel 
  through the longer path length of the scintillators. I think Khem says now he has two ways of replaying--one like before with the AND and without it. I am not clear about what he is actually doing here.

2) We also talked about how much target length we should use in the final analysis. Khem says there is not sufficient number of dummy runs to subtract out the windows every time. We will have to look at the data with various cuts on vz to decide how much window to cut out.

3) We talked about the beam energy and what to do about those runs before the lock was on. This would be mostly Kinematics A (20.5 degrees) which we did not repeat later on. The correct beam energy must be used in the replay of the data run by run -- so we will be too far off the determination of threshold.  Khem says he using the Tieffenbach values from run to run. How good is this. The bins in W will be around 1 MeV  wide. If the energy varies by more than say 200 KeV it won't be too good near threshold.

4) Khem implemented the HRS focal plane variables he got from Vince and says it is working. This was to improve our determination of the HRS acceptance since Khem was in correctly assuming the acceptance was more or less uniform in the phi, th, and p variables over the central region of acceptance.

5) KHem has 2 (or 3) cross section replays in progress with about 50 jobs in each that will take  a few days to complete. He started with 20.5 degrees and 16.5 degrees.
He is limited to how many he can submit. He will ask Cole, Nilanga, Pong, etc to submit jobs under their name to get around the limitation he is up against. He has about a 1000 jobs to submit. He will make the cross section data available as soon as these runs are done.

6) The elastic DWBA code I am using for Carbon has a precision problem somewhere in the subroutine that calculates the Coulomb functions. I am trying to get help from Wright who wrote it to see what is wrong. Do you guys have  a better code? Khem has not done anything with Carbon elastic or Tantalum and they will be useful checks for the HRS.

7) Cole points out that the simulation code does not treat the beam energy correctly. That is--- it does not allow for a thrown probabiity distribution in vertex position or beam energy due to energy loss in the target. He say he can fix it.

Please submit comments to Khem or Cole or me for clarification.

Dr. Richard Lindgren
Physics Department
University of Virginia




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