[Clascomment] OPT-IN: Subthreshold photoproduction of phi mesons from deuterium

[Reinhard Schumacher]

Hello All,

I have read the draft paper by X. Qian et al on \"Subthreshold
photoproduction of phi mesons from deuterium\".  I am surprised that
this draft has risen to the level of Collaboration review.  In my view
it is scarcely ready for publication.  Let me outline my issues with
the draft paper.

The actual scientific result of this paper is very modest (Fig. 4),
but the introductory discussion is strongly worded, promising broad
relevance of the following discussion (page 1), but also almost
totally irrelevant to appreciation of the results.  I would suggest
rewriting the first introductory 3 paragraphs to focus more on what
you actually did in this measurement, and leave out (or greatly
reduce) the gloss about the most grand issues in QCD.  This paper has
nothing to add to the grand issues, and I strongly recommend not
promising more than you can deliver.

For example, the reader finds in the very first sentence \"As mediators
of the strong force, gluons play an important role in the structure of
the nucleon.\"  Your result has nothing new to say about either the
structure of the nucleon or gluons.  Thus, the reader is misled from
the beginning about the significance of what you are about to present.
As another example, at the end of the first paragraph you gratuitously
insert a sentence about the future existence of an experiment to
search for hybrids.  This is totally irrelevant to your message in
this paper and only serves as a distraction.

Another example of the distracting introductory material that I think
you can remove is Figure 1.  The simulation you show the reader is for
copper, not deuterium, hence not really relevant to this paper.  It
shows that the sum of scaler momenta can in some cases distinguish
production channels.  However, this is not the method you are using in
this analysis, so again it is irrelevant to the message of this paper.

To first order, the paper could begin with paragraph 4 on page 2.

At the bottom of page 2 you point out that the threshold for phi
production is at 1.57 GeV, but soon the reader finds that you select
the photon energy range of 1.65 to 1.75 GeV for the results you
report.  Thus, your results are not \"sub-threshold\", but \"near
threshold\".  Am I missing something here?  You owe it to the reader to
acknowledge this, and to comment on its meaning for interpreting your
results.

The discussion around Equation (2) could be made more convincing.  The
reader is not given a picture (literally) of what the proton cross
sections look like, or how good the fits are.  By introducing the
equation and the \"a_i\" parameters you are saying they are somehow
important to the results.  But you don\'t show them in either a
graphical or a tabular form, so there is little value in introducing
this to the reader.  I think you should either complete this
discussion or leave it out altogether.  I assume the technical review
checked that this all makes sense, but your draft paper raises a
pretty big ref flag in the mind of the reader at this point.

The discussion of the \"special cut\" on the quantity E_gammaboost
starting at the bottom of page 3 column 1 is pretty opaque.  You say
you *select* the near-threshold region by requiring this boosted
photon energy to be *greater than* 1.75 GeV.  I would have thought it
should be LESS than this amount.  Is there some way you can make all
this more clear to the reader?

In the later part of the same paragraph, I am afraid I don\'t
understand the origin of the \"cusp\" and how it is related to
E_gammaboost.  In fact, the theoretical calculation is not described
in any detail at all.  The paper would be better if you did this.
This is crucial to your message because your claim is that these
results provide a \"benchmark\" for future experiments on heavier
nuclei.  Indeed, how well the results compare with simple theory is
the measure of whether you can say that the results on deuterium show
that our understanding of a simple process is under control.  At a
minimum, give the reader a literature reference to the \"simple
theoretical calculation\" you are adapting.  Alternatively, as the
author of the model (Jean-Marc?) to provide a paragraph of discussion
for this paper.

One final complaint: you have 11 lead authors listed, some of whom I
don\'t recall giving talks on this subject at Collaboration meeting on
this or any other topic.  We generally have just a handful of lead
authors on CLAS paper.  Were all these people really crucial to
obtaining these results?  

Looking forward to the next draft,
Reinhard