[Clascomment] [EXTERNAL] Re: OPT-IN: First CLAS12 measurement of DVCS beam-spin asymmetries in the extended valence region

Wed Oct 5 17:37:32 EDT 2022

Hi Maxime,

sorry it took me a while to get back to reading the paper. It’s fine by me now - obviously it’s your prerogative to choose how to present the data (I would have chosen differently).
The only small item left: The text starting in (now) line 155 is fine, except the word “entangling” in line 156 is a bit confusing - do you mean “including”? Not important, though.

Good luck with the publication! -
- Sebastian

On Sep 19, 2022, at 9:25 AM, DEFURNE Maxime <Maxime.Defurne at cea.fr<mailto:Maxime.Defurne at cea.fr>> wrote:

EXTERNAL to ODU: This email is not from an ODU account. Do not click links or open attachments unless you recognize the sender and know the content is safe.
Dear Sebastian,

Thank you very much for your careful reading of the article.

It is always frustrating to write a PRL: The length of the article is too short so between the mandatory introduction to DVCS, the desciption of CLAS12, very little space is left for the real analysis work and the results/discussion part. Before writing the article, we thought about the conclusions we wanted to highlight:
1) We have collected a lot of statistics in a very short amount of time: Indeed CLAS12 was designed to run at much higher luminosities compared to CLAS.
2) We have extended by quite much the phase space compared to the 6 GeV era.

For the 1) we could indirectly compare with CLAS6 with the reweighting procedure at the cost of having to include some explanations about reweighting.

For the 2), we have specifically chosen extreme bins in the phase space with very nice statistics. So we picked  a low xb but much higher Q2 than what was achieved with CLAS12. This bin shows a remarkable agreement with KM15 by the way, especially considering the very small statistical accuracy of points. Then we have chosen two bins at very high Q2 and xB.
But, from a phenomenology point-of-view, we cannot say much about the data. Adding more data points in the article without being able to comment them ( i.e. their Q2/xb/t-dependences), we thought it might undermine the paper.
Now, it is the first paper. It took quite some time to be familiar with CLAS12 and the subtleties of pass1-reconstruction. For the next DVCS article, I think my PhD student will have time to do him/herself a global fit instead of using reweighting techniques.

Regarding your minor comments, please find in attachment the new article version taking them into account (But I remind that this new version already includes Stepan's and Dan's comments.)
-For line 84, we already had a discussion with the AdHoc committee about the spelling of Cerenkov. We decided to stick to the orthograph in his paper, i.e. \v{C}erenkov.
-For line 158, I re-arranged the paragraph to introduce that it was a discussion about systematic on pi0 subtraction. I also introduced sigma_f as you suggested. Is it better now?

Kind regards,

Maxime

________________________________
De : Sebastian Kuhn <skuhn at odu.edu<mailto:skuhn at odu.edu>>
Envoyé : mardi 13 septembre 2022 21:11:50
À : clasmbr at jlab.org<mailto:clasmbr at jlab.org>; clascomment at jlab.org<mailto:clascomment at jlab.org>; silvia at jlab.org<mailto:silvia at jlab.org>; guidal at ipno.in2p3.fr<mailto:guidal at ipno.in2p3.fr>; daria at jlab.org<mailto:daria at jlab.org>; rafopar at jlab.org<mailto:rafopar at jlab.org>; DEFURNE Maxime; guillaume.christiaens at cea.fr<mailto:guillaume.christiaens at cea.fr>; schmidta at jlab.org<mailto:schmidta at jlab.org>
Objet : OPT-IN: First CLAS12 measurement of DVCS beam-spin asymmetries in the extended valence region

Greetings! Overall a very nice result and a nice paper. I have only one major concern: The section "Results" does not show much in terms of actual data and spends too much space (imho) on an explanation of ANN and reweighing. I would prefer a kinematic plot that shows all the bins in x and Q2 (and perhaps even t) for which we have new data, with older data kinematic coverage indicated. Fig. 4 does show that we improve the precision of our knowledge of CFFs in the region where we already measured with CLAS6, but maybe it could be "de-emphasized" relative to the large new kinematic coverage. Another option would be to increase Fig. 5 by showing the same x/Q2 bins, but for several t-bins (e.g., 3 rows with 3-4 plots each). I realize that the complete data will be in the Supplemental Material, but my preference is to show more of our data in the Results section.

Here are some minor comments (with line numbers):
16 - ...nucleon structure, including THE composition of [leave out "its"] spin and pressure distributions within [leave out "it"].
21 - ...and a change in the nucleon's momentum after reabsorption of the parton expressed in the Mandelstam variable t.
36 - ...leading order in PERTURBATIVE Quantum Chromodynamics (pQCD)..."
38 - In the experimentally indistinguishable Bethe-Heitler (BH) process, ..
47 - ... interference term BETWEEN THE AMPLITUDES FOR both processes.
50- remove "a", and at the beginning of line 51, "from it".
84 - Pavel Alekseyevich Cherenkov is Russian and not written with a Czech letter.
89 -: Seems a bit redundant with the previous sentences. Maybe instead: "Scattered electrons are detected in the forward part of CLAS12. About 80%..."
158ff: I am a bit confused by the discussion of pi0 contamination. In line 163 you quote sigma_pi = 10% - of what? (percentage must be relative to something). Is it the relative uncertainty on "f"? Shouldn't it then be "sigma_f"? In any case, Eq. 2 needs to be consistent with how you define these quantities. You might also want to FIRST state that the following is a discussion of systematic uncertainties, before you introduce sigma_pi.
Fig. 4: If you keep it this way, maybe the caption could be a bit clearer that only the ANNs are reweighed, not KM15. Maybe "...and PARTONS ANNs. The latter are shown both before and after..."

Other than that, full speed ahead.
<DVCS_PRL-sebastian.pdf>

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