[Clas12_rgb] concerning figure 5 of nDVCS paper draft, VGG predictions compared with our data

Sebastian Kuhn kuhn at jlab.org
Wed Jun 5 08:38:20 EDT 2024


Just a quick question: Why are all the preferred values for J_u negative and for J_d positive? This seems very counter-intuitive, given that the quark helicity contributions to J have the exact opposite sign. This would require enormous (overcompensating) orbital angular momenta to explain.

- Sebastian

> On Jun 5, 2024, at 4:07 AM, ajhobart via Clas12_rgb <clas12_rgb at jlab.org> wrote:
> 
> Dear Valery, RGB,
> 
> following our discussion during the last RGB meeting concerning figure 5 of the nDVCS paper draft, we have performed a scan using VGG of different values of Ju and Jd and evaluating for each set a chi2 with the 9 data points that we extract with our analysis. Indeed, this scan has shown that there are other values of Ju and Jd that are more "preferred" by our extracted harmonics than the ones we had initially put in the paper. We have updated figure 5 accordingly (I attach it here also).
> 
> color code for figure 5
> 
>     //   ju       jd      reduced chi2
>     //-0.45    0.2  3.03423                blue
>     //-0.25    0.15 3.19268               black
>     //-0.2      0.15 3.1004                 Red
> 
> Attached also you will find the plot with Ju, Jd and chi2 value for each set as you requested. It seems that there is a particular preferred range for Jd (around 0.15) but none for Ju.
> 
> 
> thanks
> 
> Best regards
> 
> Adam
> <bsa_q2xbjt_coloronline_newVGG.pdf><jujdchi2.png>_______________________________________________
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