[Clascomment] OPT-IN:Measurement of the Differential and Total Cross Sections of gd -> K0 Lambda(p) Reaction within the resonance region

[Charles Hyde]

Excellent paper.
Typographic (and a few physics) comments/questions

Institution list:  "Jefferson National Laboratory"  does not exist.  Use Jefferson Laboratory, of Thomas Jefferson National Accelerator Laboratory.

Section I. Introduction
2nd paragraph:  I am not sure if the theory purists would agree that KaonMaid [4] is an “effective Lagrangian model”.  Perhaps it is better to say it in a unitarized tree-level Lagrangian model?

A little later in this 2nd paragraph, the word “change” is supposed to be “charge”:
“Since the $K^0$ has neutral charge and no spin…”

3rd (last) paragraph is weak.  I think you are underselling the recent data and PWA analyses.
The text implies that all that has been done is bump-hunting.  Also, there is no point in using the word “photoinduced” when everywhere else you use “photoproduction”
Possible change:
“However, the SAPHIR [11,12] and CLAS[5—7] photoproduction data off a proton target show an enhancement at $W\sim 1.9$ GeV.  Partial Wave Analyses (PWA) demonstrate that this corresposds to a new resonance, the $N(1900) 3/2^+}$, which couples only weakly to 
$\pi N$ or $\pi$N^*$ final states [2].”

Section II. The Experiments
The first paragraph ends at the end of the first page with a sentence fragment:
“This allow tagging… energy with resolution”
Where is the rest of this sentence?

Section II.B. g13 Experiment
Midway through the first paragraph:
“A 40 cm unpolarized … target was used for both g13a.”
Do you mean “both g13a and g13b”?  or both energies of g13a? or …?
2nd to last sentence of first paragraph:
“The larger subset of g13a…”
Larger than what?  Do you mean “the largest subset”?

Section III.A. Particle Identification
After eq’n 1, change
“the assumed mass of the each particle,”
to
“the assumed mass of each particle,”

Fig. 6. (g13 data)
Perhaps the dashed line and annotation “Missing $p\pi$” would be more visible if the line and font colors were white?
The last sentence of the caption would be clearer if rephrased as
“The edge of the missing-$\pi N$ phase space is indicated by the black (white??) dotted line arbitrarily drawn at $MM(\gamma d,\pi^+\pi^-\pi^- p) = 1.08\text{ GeV/c}^2$ (for a target neutron at rest).

Section III. C. Yield Extraction
3rd paragraph (top of page 5)
The first two sentences are fine.  The rest of this paragraph is vague and confusing.
Is there something that you are trying to say here that is not said (in more detail and greater clarity) in the subsequent paragraphs and sections?
Is so:  Please rephrase!
If not:  I suggest deleting the rest of this paragraph, and use the first two sentences as the intro to the text of the following (final) paragraph of this section.

Section III. D. Background
I am very confused by your definitions and discussions of “five track background” and
“four track background”
I have suggestions to improve the intro and sub-subsections 1. and 2.
Please remove all references to “n track background”.
Replace with e.g. “background channels with four charged particle tracks” or
“background channels with four detected charged particles”, etc.
I don’t understand the labeling “four track” and “five track”.  Both classes of background have 5 charged particles, with only 4 charged particles detected.

Suggested Revisions
Intro paragraph:
The reaction of interest… decay products of … are detected.  Therefore, the detected final state particles are $pi^-\pi^+\pi^-p$.  There are two classes of background channels that will also produce events with this same four charged track topology.  The first background class are events with an excited hyperon or kaon in the intermediate state. The second background class has only non-strange intermediate states.

1.	 Backgrounds from excited hyperons and kaons
By extracting the yield by selection on the mass of the missing baryonic system, it was likely that any process producing an extra pion (or other additional massive particle) was well separated from the spectator proton missing mass measured by …. given particle.
Near  the $MM(K^0\Lambda)= M_p$ signal, the most prevalent open-strangeness background channel was identified as 
$\gamma d \to K^0 \Sigma^0 p \to K^0 \Lambda (\gamma p) \to \pi^-\pi^+\pi^- p (\gamma p)$.
Nonetheless, other background channels were also explored.

2.	Backgrounds without open strangeness
The strangeness channels of exclusive $K^0\Lambda$ and $K^0\Sigma^0$ are the primary source of our four detected charged-track events with missing mass at or near the proton mass.  Nonetheless, other non-strange production channels may contribute a background to the exclusive (or near-exclusive) signal.   One could imagine…

After Eq’n 3 (bottom of page 6)  I don’t understand the “15%”:
“The size of this background fluctuated near 15%, depending on the…”
Do you mean “the background varied from 0 to 15% of the signal”?
Or “the relative size of the background varied by 15% around its average…”?
Or ??

The last sentence sub-subsection III.D.2 could be improved:
Change
“This resulted in the raw yield of $K^0 \Lambda$ after subtraction of $K^0\Sigma^0$ events”
to
“The yield of $ of $K^0 \Lambda$ events is obtained by subtraction of the estimated of $K^0\Sigma^0$ and non-strangeness $ to \pi^-\pi^+\pi^- p$ events from the total $K^0 \Lambda$ within the selection window of Fig. 7.

Section III.E. Photon Flux
Please clarify the sentence
“Most energies showed a variation less than $3\%$ in normalized yield for g13a ($\approx 5\%$ for g10). “
Is this a bin-to-bin fluctuation in photon energy or simply a systematic fluctuation for the three different incident electron energies?

Section III.F. Monte Carlo Simulation

First paragraph.
Second sentence:  change
“blind spots and low regions of efficiency.”
To
“blind spots and regions of low efficiency.”
Further down in this paragraph: change
“The reliability of the simulated events were tested…”
to
“The reliability of the simulated events was tested…”
The subject of this sentence is the singular “reliability” not the plural “events”.

Section III.G. Uncertainties
Last full sentence on page 7.  Change
“…where statistics and detector efficiencies are poor”
to
“….where statistics are low and detector efficiencies are poorly known”
or
“…where detector efficiencies are poorly known”
or???
Neither “poor statistics” nor “poor efficiency” has quantitative meaning.
(you have already said that there are forward regions where the efficiency is zero)

Fig 12, the “dots” look more like “open circles” when I blow them up big enough for my poor 60.5 year-old eyes can see them.

Fig. 13
Caption, fix a latex-ism (\cos) and wording:
Change
“at three $z = cos(\theta_{CM}^{K^0})$ locations.”
To
“at three $z = \cos(\theta_{CM}^{K^0})$ values.

Are these fits from the Bonn Gatchina group?  If so, reference them directly in the caption.
Please identify the source of the red and black data points (g10 and g13a, or vice versa??)
I don’t understand the meaning of the three (or four) fit lines/bands.
The legend identifies three channels, but the figure looks like total fit plus two sub-channels.
OK, after expanding the fig x5 I can distinguish green and blue shadings.  
You have lots of space.  Figures 14, 15 are large.  Fig. 12 is less important than Fig. 13.
I suggest stacking the three figures of Fig 13 so that each sub-figure occupies an entire column-width.  Then we will be able to see all of the data and fit details.  In text or caption, you need to more completely describe the contents of this figure.

Section IV.A
See previous remarks on Fig.12 and 13.

Fig. 15 caption
I suggest:
“The g10 (circles, black online) and g13a (squares, red online)…”
Second sentence rephrase discussion of BnGa fits:
“The Kaon-MAID model (dashed line)… along with the two preliminary BonnGA $K^0\Lambda fits (the shaded band indicates the difference between the two BnGa solutions).”

Section IV C. Total cross section
Second paragraph after the five bullets:
“These specific functions can fit the data well and ARE assumed…”
Next paragraph, there is a missing figure reference:
Fig. ??
I presume this is Fig. 18

Bibliography
Items 19-26
You can clean up the titles of these technical notes by putting the title text in
{…} braces in the .bib file
[24] S. Stepanyan, “fsgen,” (2006) needs a more complete reference (is this a technical note that is available publicly?)
ditto for [26] Holtrip (no year even)