[Halld-npp] Minutes posted and the Overleaf document has been updated

[Elton Smith]

Dear collaborators,

I have posted some minutes of today's meeting on the wiki at 
https://halldweb.jlab.org/wiki/index.php/Pi0_Polarizability_Meeting_Jun_12,_2020#Minutes.

I have also updated the draft on Overleaf with the latest changes. 
Please provide feedback as soon as possible so that we can post an 
update for the collaboration early next week.

Note: I updated the summary plot (Fig. 29 of the proposal). We state 
that the (statistical) uncertainties are obtained directly from the fit 
(Fig. 21). It turns out the AmpTools fits provide very reasonable errors 
near threshold where the statistics are large, but give very small 
uncertainties at high mass. If we use the fitted statistical 
uncertainties directly, I get the attached plot. One can see that at 
large masses, the uncertainty converges to the 5% systematic 
uncertainty. There are only 10-20 Primakoff-pi0pi0 events in this mass 
region. This is very likely an underestimate of the true statistical 
uncertainly. [Note that this is a well-known fact of the output of the 
Amplitude fit.] Therefore, I have produced a hybrid plot, where I use 
fitted errors where the statistics is large and the "naive" statistical 
uncertainty if the fitted uncertainty is very small. The plot that is 
included into the document uses the latter strategy. We can talk about 
this next week.

Cheers, Elton.

-- 
Elton Smith
Jefferson Lab MS 12H3
12000 Jefferson Ave STE 4
Newport News, VA 23606
(757)269-7625
(757)269-6331 fax

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