[Clascomment] OPT-IN: Cross sections for the exclusive photon electroproduction on the proton and Generalized Parton Distributions

[Hyon-Suk JO]

In addition to the changes already listed by Michel Garcon in the email 
below, here is a list of the latest changes in the paper draft that can
be found here:
https://www.jlab.org/Hall-B/shifts/admin/paper_reviews/2015/dvcs_cross_sections_prl_draft_v4-5413120-2015-03-31-v4.pdf

===
Throughout the paper: Replaced the GPD model name "GK" with "KMS".

Abstract l.4-5: Replaced "describe the data well" with "describe
the data well at most of our kinematics".

l.8-9: Replaced "in the universe" with "in the visible universe".

l.24-25: Replaced "from a lepton beam" with "from the lepton beam".

l.43: Replaced "In a frame where the nucleon goes" with "In a
frame where the nucleon moves".

l.37: Replaced "One speaks of nucleon tomography" with "One uses
the term nucleon tomography".

l.89: Replaced "our results formidably enrich the existing set"
with "our results strongly enhance the existing set".

l.98: Added Ref. [18].

l.239-240 and l.262-263: Replaced "Integrated over our 110
(Q2,xB,t) bins, the chi2 value per degree of freedom" with "Over
our 110 (Q2,xB,t) bins, the average chi2 value per degree of
freedom [33]", with Ref. [33] added as a footnote "The chi2 values,
integrated over all the bins, give a general indication but the
level of agreement or disagreement between each GPD model's
predictions and the data varies as a function of the kinematics."

l.321: Replaced "This considerable set of new data" with "This
large set of new data".

l.324-325: Replaced "describe well the data and do not need
additional inputs" with "describe the data well without additional
inputs".

l.336-337: Replaced "The present data" with "The full data set".
Replaced "A longer article [40] will include the presentation of
our results for all" with "A long article is in preparation and
will include the results for all".

Added the following in the acknowledgments:
"This work benefited from the support of the French Agence
Nationale de la Recherche (contract ANR-12-MONU-0008-01 PARTONS)
and the Joint Research Activity GPDex of the European program
Hadron Physics 3 under the Seventh Framework Programme of the
European Community."

Removed the following from the acknowledgments (wrong contract
number): "The Southeastern Universities Research Association
(SURA) operates the Thomas Jefferson National Accelerator
Facility for the U.S. Department of Energy under contract
DE-AC05-84ER40150."

Added Ref. [18]: "G. Gavalian et al. [CLAS Collaboration],
Phys. Rev. C 80, 035206 (2009)".

Added Ref. [33] as a footnote:
"The chi2 values, integrated over all the bins, give a general
indication but the level of agreement or disagreement between each
GPD model's predictions and the data varies as a function of the
kinematics."
===

Thanks again to all for your comments!

Cheers,
Hyon-Suk

On Tue, 24 Mar 2015, Michel GarXon wrote:

> The lead authors would like to implement these changes:
>
> - We should be more cautious on the statement in the abstract (last sentence) on "nearly model-independent...". We omitted here to say "leading-twist", which is a key word. As soon as higher-twist (and higher order)are considered, the extraction is no longer "nearly model-independent". We will replace "nearly model-independent" by "leading-twist", and leave the qualification of the extraction for the text, not the abstract. (see below comment on l. 271). Besides, the model-independence refers to the GPD (or CFF) themselves, not to the framework within which the amplitudes are calculated.
>
> - l. 34-35: "in terms of four-vectors in an obvious way" is not so well said. What about "in terms of the electron and proton four-vectors" ?
>
> - l 271: it really is here leading-twist and leading-order for DVCS (order refers to the pQCD expansion in alpha_S, twist refers to the QCD/OPE expansion in 1/Q). We propose: "At leading-twist and leading-order, this procedure uses well established DVCS amplitudes and does not depend on model parameterizations of the GPDs. We fit simultaneously...."
>
> - l 309-310: b is indeed linked to the transverse size of the nucleon, but is not directly the transverse size (there are kinematic-dependent proportionality factors). It could be confusing if somebody tries to quantify the transverse radius as 1/sqrt(b). We would replace "interpreted as" by "linked to" or another expression to the same effect. Or "related to" might be better. The exact mathematical expression would lead us too far.
>
> - Remove ref [40], which is useless as is.
>
> -	+ miscellaneous syntax changes.
>
>