[Clas12_rgb] concerning figure 5 of nDVCS paper draft, VGG predictions compared with our data
ajhobart
ajhobart at jlab.org
Wed Jun 5 09:39:24 EDT 2024
Hi Sebastian,
For figure 5, the limit on the reduced chi2 that I put affects the set
of accepted sets of Ju and Jd. The Limit is now 3.5, if I move it ot 5 I
have a set of accepted sets of Ju and Jd that contains positive values
of Ju (50% of selected fits). So maybe it is our choice that gave the
impression that only negative Ju values are reasonable!
My reasoning is that there are preferred values for Jd (positive around
0.15) but no preferred values for Ju, I attach here again the same plot
showing Ju vs Jd versus chi2 from a different angle. It shows that on
the Ju axes, the distribution for chi2 is almost Flat.
However, my take on this is that rather none of the combinations of Ju
and Jd reproduces the data correctly. Even for the ones we chose to put
in the figure 5, it is quite clear that the trend seen in the data is
not consistant with the curves. Moreover, VGG predictions remain model
dependant predictions and we do not intend to consider them as a strong
physics conclusions on the values of Ju and Jd.
thanks
Best regards
Adam
Le 05/06/2024 à 14:38, Sebastian Kuhn a écrit :
> 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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