[Halla_pi0] pi0 meeting 1:30 PM

[richard lindgren]

Summary of pi0 meeting

Khem will plot up HRS vz reconstruction for carbon target and dummy foils as a function of HRS angle
and look for any angle mispointing effects. Check for momentum/angle  dependence. If the effect is less than 1-2 mm on average, it will suffice to make correction by using a simple multiplicative factor for target thickness. 

Khem will make y and/or momentum correction to BigBite reconstruction of vz until it fits HRS reconstructed value (5.9 cm). I don't understand what cuts Khem is making that he referred to in the meeting to minimize unknown fringe field effects when determining vz. What are these cuts?

Cole is helping to fit the pi0 Mainz data to determine if there is any d wave present. He is also fitting the Mainz data with the UVa_ChPT code to extract the LET constants. The presence or absence of d waves will alter the value of any LET constants.

After the meeting we talked more with Khem about the calculation of the cross sections. Last time he binned the data in 20 degree angles in both theta and phi. He last binned the data in 1 MeV bins in W. Although the resolution in W is worse and closer to 1.5 to 2 MeV, we will bin in 1 MeV bins again and make corrections later or simply add them together for 2 MeV. We emphasized the importance to him to make sure he bin the data down to a few MeV below threshold until we see 0 pions produced. Our binning in Q2 is  0.01 GeV^2. except for the first bin where he binned it in 0.005 GeV^2.

Then we discussed making poor resolution corrections to the yield from the bins. He plans to calculate a bin correction factor by using Vladimir's code ( Monte Carlo Simulation with absolute cross sections calculated from  ChPT or MAID) including fringe field. By taking the ratio of the input - exact cross section summed over 1 MeV -  divided by the  simulated output including proton energy loss/straggling/ in the target and bigbite and the wire chambers. He will get a correction factor to divide the actual data by.  Vladimir does include bremstrahlung in the target, but not in the HRS air gap or S1 and S2 scintllators etc. Also not included is proton nuclear scattering in the wire chambers and scintillators. I think this is a small effect at low proton energies.

I appreciate any comments

Richard






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