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

[Daniel Carman]

						April 5, 2010


Xi and Haiyan et al,

I have read through the draft of your phi meson paper. I have a few
physics questions that bothered me as I read through your draft. I
include them below along with other things that I found. Let me know 
if you have any questions or need any clarification.


				      Regards,

				      Daniel

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Page 1.
  Left Column.
    Paragraph 1.
      Line 9. Use \"low-energy\".
    Paragraph 2.
      Line 2. Remove comma after \"suppressed\".
      Line 5. Use \"... nucleons are a rich source ...\".
  Right Column.
    Paragraph 2.
      This paragraph is too long. To help with readability, I suggest to
      separate it into several paragraphs. The first new paragraph could
      begin at Line 11 with the sentence \"For this kind of search ...\"
      and the second could begin at Line 25 with the sentence \"The best
      way ...\". This will help with readability.
      Line 22. Use \"... channels a) and b) ....\".

Page 2.
  Left Column.
    Paragraph 3.
      Line 13. Reaction not written in proper order. Use d(\\gamma,phi p)n.
      Line 16. Use \"... [17], and [18].
    Paragraph 4.
      Line 1. Use \"... $K^-$, and the proton ...\".
      Line 8. Kind of awkward here. I suggest \"... polarity setting (that
        favored detecting positively charged particles), ...\".
  Right Column.
    Paragraph 1.
      Line 1. You point to Fig. 2 to convince the reader that the energy
        bin from 1.65 to 1.75 GeV is below threshold for phi meson 
        production based on the g11 result from hydrogen. You refer to the
        right panel of Fig. 2. However, there is a clear phi peak (or
        shoulder or remnant). You cannot make such a claim based on what
        is shown here. Given the very limited statistical quality of your
        data points here, assumptions like the 1.75 GeV \"threshold\" leave
        me dubious of your results.
      Fig. 2. Are these mass plots acceptance corrected? If not, they should
      be given what you are trying to show.

Page 3.
  Left Column. 
    Paragraph 1.
      Line 5. Add a reference for the Bonn potential.
      Last sentence. Very awkwardly written. \"The MC events were generated
        based on a Breit-Wigner shape of the resonance centered at the
        $\\phi$ mass of 1.019 GeV/c$^2$ with a width (FWHM) $\\Gamma$=4.26
        MeV/c$^2$. The $\\phi$ meson decay angular distribution and cross
        section are based on the g11 data [20].\".  I would then slightly
        modify the sentence starting the next paragraph as follows:
        \"The $\\phi$-meson photoproduction differential cross section on a
        hydrogen target from a fit to the g11 data used the form: ...\".
    Paragraph 2.
      Line 5 after Eq.5. What do you mean \"events were updated\"?
    Paragraph 4.
      - Line 4. Use \"Here $E_{\\gamma boost}$ is the ...\".
      - I am not particularly satistified with the explanation of the cut
        on the Egammaboost quantity. A plot showing the distribution would
        be possibly helpful to show why this value was chosen to separate
        subthreshold production.
  Right Column.
    Fig. 3.
      What is the solid line on the figure?
      Caption line 4. Use \"$N-N$\".
    Paragraph 1.
      Line 11. Awkward sentence here. I suggest \"In addition, our data
        have been ... with the $\\phi$-meson photoproduction differential
        cross section from the proton based ...\".
      Line 15. I have no idea what you are talking about with the \"cusp\"
        business.
    Paragraph 2.
      - You quote ranges of systematics for each source, but you only have
        3 data points. This seems worrisome that systematics would vary over
        such a large range between a couple of points. I don\'t believe it.
        Given that your statistics are few, are the variations not more likely
        statistical effects?
      - You compare two approaches to subtracting the background and find
        a difference of yields between the two of 8%. You did not say what
        the assigned systematic was. I assume 8%, but is this reasonable?
        Are both functional forms reasonable descriptions of the data?
        Given that you only have 3 data points, why don\'t you show the
        fits?

Page 4.
  Left column.
    Paragraph 2.
      Line 11. Pinning the discrepancy between the \"theory\" curve and
       the data as due to FSI seems to be quite a strong statement given
       the toy nature of the model and the severe limitations of the data.
  Right column.
    Paragraph 1.
      Line 3. You state that these data also provide important information
        on physics backgrounds. What important information are you refering
        to here?

References.
[7] Typo on last authors name.
[11],[12] Add comma before \"and\" in list.