[Clascomment] OPT-IN:Target and Double Spin Asymmetries of Deeply Virtual Ï0 Production with a Longitudinally Polarized Proton Target and CLAS

[Viktor Mokeev]

Thank you Andrey!

 I agree with your considerations.

  Best Regards,
                     Victor

----- Original Message -----
From: "Andrey Kim" <kenjo at jlab.org>
To: "Viktor Mokeev" <mokeev at jlab.org>, "clasmbr" <clasmbr at jlab.org>, "clascomment" <clascomment at jlab.org>, "Harut Avakian" <avakian at jlab.org>, biselli at jlab.org, "burkert" <burkert at jlab.org>, maurik at physics.unh.edu, "Kyungseon Joo" <kjoo at phys.uconn.edu>, wooyoung at jlab.org, voutier at jlab.org
Sent: Wednesday, October 21, 2015 2:34:25 AM
Subject: Re: OPT-IN:Target and Double Spin Asymmetries of Deeply Virtual Ï0 Production with a Longitudinally Polarized Proton Target and CLAS

Dear Victor,
Unfortunately, we can't rule out the possibility that there are other 
than hand-bag diagram contributions. But because the models are 
under-constrainted we can't neither deny nor confirm these possiblities. 
The discrepancies between models and data come from model 
parameterezations. But they could also come from other contributions.

I changed the "fair agreement" statement to the "better agreement". The 
main claim here is not that the theory can describe the data perfectly 
but that the inclusion of chiral-odd GPDs bring it to better agreement 
with data. However, the GPD parameterezations are very model-dependent, 
chiral-odd GPDs are even more so. Therefore discrepancies between the 
data and models are expected at this stage since there are very few 
contraints exist. And the new data that provide these constraints are 
very needed as you pointed out. In the future when we will have more 
experimental data to better constrain GPDs we would be able to answer 
your question.
Thank you,
Andrey.



On 10/04/2015 02:41 PM, Victor Mokeev wrote:
>    Dear Colleagues,
>
>   Your paper is very nice and very needed in order to get access to the structure of the ground nucleon state in 3D and offer valuable constraints for the subsequent studies of excited nucleon state structure in terms of the transition N-->N* form factors.
>
>   However I would propose to re-write the part:
>
> p.4 left strings 278-282
>
> How we may claim the GGL (not GL to be consistent with the previous text)) is in ``fair agreement" with the measured asymmetries, if three of four measured asymmetries are very different from both model predictions, up to factor of 3 at t>1.0 GeV^2, as it can be seen in Fig . 4.?
>
> In my view, these discrepancies may be the evidence for the contributions from other than hand-bag diagrams, because of interference between hand-bag and other than hand-bag diagrams. Can you rule out this opportunity?