Meeting No. 10

Determination of the proton radius:

So far we have used dipole approximation to fit our data. This model is not good. After our discussion with Jan and Michael in March, I have modified my model, by adding second and third derivative term into our model. These two additional terms are fixed and take care of the correct curvature of the GE curve. The parameters are taken from the Distler et al. paper. I have also considered the errors of these paremeters to determine the Model part of the uncertainty of the radius.

FitFormFactorsEducated.pdf

I have also considered the systematic uncertainty of the FF extraction to determine the systematic error of the radius. I have used Mathematica to simulate the effect. The uncertainty is approx 0.04fm.

All these results are obtained without the three elastic points!

The Vertex correction:

After the discussion with Marc I have added Vertex diagrams for the elastic events to my simulation. The correction was of right sign and order. First I corrected directly the results in the histograms (shifted the first two bins), to get the feeling for the effect. However, the proper thing to do is to modifty the simulation. I have added the correction. This correction depends on one paramters, the dE cut, that defines, which events are still elastic and which not. At the moment I set the cut to 2E-3MeV to match the 495MeV setting. With the same cut the results for the 330MeV setting also work well. However, At the moment I am struggling with the 195MeV setting, where the correction does not work well and I do not know why. Work in progress.

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Optics:

Now for more than a week I am running full minimization for Spectrometer A at the 360MeV setting. The minimization is time consuming because of the many matrix elements and many data points, ie, SVD matrices are large.

Last modified 13.5.2016