Estimation of Nucleon D-Term in QCD
Round 1
Reviewer 1 Report
In this manuscript the light-cone sum rules (LCSR) are used at leading order
to obtain a "preliminary upper estimation" for the nucleon gravitational
form factor D(t) which is sometimes also referred to as the D-term form
factor. The manuscript contains several unclear points which should be
addressed.
1. The term "upper estimation" is not clear. Does the author mean that
his result is an estimate for the upper limit for D(t)? Does this mean
that D(t)_{correct result in LCSR} \le D(t)_{estimated here}? If yes,
which terms have been neglected? How does the author know which sign
the neglected terms have? It is important to explain this point.
2. In the lines 54-56 the author "argues" that in order to extend the
preceding calculations performed for electromagnetic form factors to the
case of gravitational form factors he has to weight the electromagnetic
form factors with the certain tensor structure.
It is not clear what this means. What is the basis for this "argument"?
Is this an assumption by the author? Is this a model? Or, did the author
derive the exact expressions for the gravitational form factors in the
LCSR approach (and found that these expressions correspond to the
electromagnetic form factors up to a "certain tensor structure")?
3. The author writes in the line 76 that his "thorough numerical analysis
shows that the unknown $\tilde{T}^{+-}_{1[\bar\psi_-\psi_-]}$ contribution
can be estimated" by the expression in Eq.(17).
It would be important to provide some more detail: why is Eq.(17) a good
approximation? How big are the neglected terms? Is there a small parameter
which justifies such an approximation?
4. Line 77: Why is it justified to neglect the C-term from the F-combination?
5. The author speaks of "analytical continuation of the obtained fitting
functions to the region of small t" in line 83. The "term analytical
continuation" cannot be used in this context. This is an "extrapolation"
to the region of small t. Such an extrapolation introduces an uncontrolled
uncertainty and model-dependence in the study. This should be remarked.
6. In the manuscript the author mentions the chiral quark-soliton 5 times
(line 11, 27, 86, 87, 107) and the Skyrme model 4 times (line 27, 86, 88, 108).
The author quotes the review [2] as a reference for these works which is not
accurate. Instead the author should refer to the original references:
K.Goeke et al, Phys. Rev. D 75 (2007) 094021
doi:10.1103/PhysRevD.75.094021
[hep-ph/0702030].
K.Goeke et al, Phys. Rev. C 75 (2007) 055207
doi:10.1103/PhysRevC.75.055207
[hep-ph/0702031].
C.Cebulla at al, Nucl.Phys.A 794 (2007) 87
doi:10.1016/j.nuclphysa.2007.08.004
[hep-ph/0703025].
Author Response
see attachment
Author Response File: Author Response.pdf
Reviewer 2 Report
In this paper the author considers the light-cone sum rules to obtain the gravitational form factor D(t) which is very important in order to understand the mechanical properties of nucleon such as pressure inside the nucleon. The results are of interest for further work in this field, and I would suggest publishing the paper in Particles provided the following minor question is addressed:
1. Fig. 1 represent the fitting of the nucleon gravitational form factor D(t) at low -t region. Is it possible to get the flavor contributions to the nucleon form factor D(t)?
Author Response
see attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The function R(t) in Fig.1 is difficult to see. Recommend to adjust the scale on the y-axis such that the function can be seen clearly. Otherwise the author has improved the manuscripts in many respects.Author Response
I thank the Referee for his remark. As you can find, the present version includes the rescaled fig.1.
With best regards,
Igor V. Anikin
Reviewer 2 Report
I recommend the manuscript for publication in Particles in its present form.
Author Response
I thank the Referee for his positive consideration of the paper.
With best regards,
Igor V. Anikin