[Primex] the latest version of the prl paper

[Barry Ritchie]

My only suggestions are intended to make the paper read more smoothly
and accurately. Where there have been multiple changes within the same
sentence or two, I have provided the suggested changes and, in most
cases, provided an example of how the final results might read. 

BTW: An occasional misusage in the paper is the use of the word "error"
when "uncertainty" is meant. The two words, of course, do not mean the
same thing. The use of "error" is colloquial and often encountered in
our conversations, but the latter word is what should be used in a
formal context such as this paper.  

---Barry

Professor  Barry G. Ritchie 
Department of Physics 
Arizona State University 
Tempe, AZ  85287-1504 
  
Telephone: (480) 965-4707 
Fax: (480) 965-7954 


===================================


ADDRESSES

1. Eugene Pasyuk should have a footnote "Present address: Thomas
Jefferson National Accelerator Facility, Newport News, VA 23606, USA"

2. If zip codes are to be used in addresses, then we should use "Tempe,
AZ 85287" for ASU. 

ABSTRACT

Some minor re-writing of the abstract will focus on the important
points:

3. In the first sentence, I suggest "Differential cross sections...have
been measured..." The words "High precision..." are only indicative of
the current state of the art, not the physics interest.  

4. We should remove redundancy in the first sentence by removing "two
nuclei" thusly: "... photoproduction at forward angles for 12C and
208Pb, have been performed..." [though again, I would say "cross
sections...have been measured" rather than "measurements... have been
performed"

5. I would append an abbreviated portion of the second sentence to the
first and reorder to emphasize the novel features of the measurement:
"...decay width with a high-resolution multichannel calorimeter and a
tagged photon beam." 

All put together, the abstract now reads something like:

"Differential cross sections for pi0 photoproduction on 12C and 208Pb at
forward angles have been measured for incident photon energies of 4.9 -
5.5 GeV with a high-resolution multichannel calorimeter and a tagged
photon beam. These measurements were used to extract the decay width
$\Gamma(\pi^0 \rightarrow \gamma\gamma)$, which was extracted by fitting
the measured cross sections with recently updated theoretical models for
the process. The resulting value for the decay width is $\Gamma(\pi^0
\rightarrow \gamma\gamma)$ = 7.82 eV $\pm$ 1.8\% (stat.) $\pm$ 2.1\%
(syst.)." 

PAGE TWO:

6. First paragraph: The use of "error" when "uncertainty" is meant
occurs several times in this paragraph. The latter is better usage (as
noted above) and also less confusing, particularly for readers whose
first language is not English.

7. First paragraph, third sentence: Use of "error" for "uncertainty" and
some other word issues: "The most accurate previously published
measurement for the \pi^0 decay width was performed at Cornell by
Browman et al. [9] with a 5.3% quoted total uncertainty:..."

8. First paragraph, fourth sentence: There is a repeated phrase and use
of "error" for "uncertainty". Should read: "This result agrees within
experimental uncertainty with the theoretical prediction."

9. First paragraph, fifth sentence: "Two other measurements [10, 11]
with relatively large experimental uncertainties..."

10. First paragraph, sixth sentence: Choose better word than "done":
"...prior to the current PrimEx experiment, was made by Atherton..."

11. I think the sentence beginning "Clearly, a new Primakoff type of
experiment..." is gratuitous, particularly considering the next
sentence, and should be removed. 

12. In the next sentence, substitute "current" for "recent". (The photon
tagger at JLab, for instance, has been in operation for over a decade.")
We should also have a paragraph break at this sentence, since we have
moved from a discussion of previous measurements to aspects of the
current measurements. 

13. Second column, first paragraph, first sentence: "...was performed in
Fall 2004..."

14. Next sentence: I would suggest "...radiation length targets of 12C
and 208Pb [14]."

15. Later on in the same paragraph, we should not use the capitalization
indicated, since the reader can easily make the association:
"...multichannel hybrid electromagnetic calorimeter (HyCal)..." In the
same sentence, remove the word "at", which is unnecessary:
"...multichannel hybrid electromagnetic calorimeter (HyCal) located 7.5
m downstream..."

16. In the next sentence, the word "calorimeter" has become redundant
due to the definition of the term HyCal, so we should write "HyCal
consists of..."

17. Further along in the same paragraph, we need hyphens: "Twelve
5-mm-thick scintillator counters, located in front of HyCal, provided
rejection of..."

18. In the next sentence, there are some word issues. The word
"distance" is used when "space" or something similar is meant, and
"covered" is used when we mean "enclosed". So we need something like "To
minimize the decay photon conversion in the air space between them, the
volume from the PS magnet to HyCal was enclosed by a helium bag at
atmospheric pressure."

PAGE THREE

19. First paragraph, first sentence: Remove unneeded commas: "The event
yield (number of \pi^0 events for each production angle bin) was
obtained from the data by applying the selection criteria described
above and fitting the experimental distributions for each angular bin."

20. First paragraph, last sentence: Use of "error" when "uncertainty" is
meant: "...largest contributions to the total systematic uncertainty."

21. Second paragraph, fourth sentence: Potential confusing word
"better". I suggest "Different techniques have been used to determine
the number of atoms in both the targets with an uncertainty less than
0.1%"

22. Since we do not "show" it here, the last full sentence at the bottom
of the first column should perhaps be an assertion: "The \omega
photoproduction process ... is the dominant contribution to the
background." (There was also a repeated word "the" in the text, by the
way.)

23. Second column, first paragraph, second sentence: Remove extraneous
commas: Two elementary amplitudes, the Primakoff (one photon exchange)
T_Pr and the strong (hadron exchange) T_S, contribute coherently as well
as incoherently in \pi^0 photoproduction from nuclei at forward angles."


24. In the next sentence, remove the unneeded capitalization:...
"Primakoff (Pr), nuclear coherent (NC), interference (Int), and nuclear
incoherent (NI):..." Also please note that we have not explicitly said
at this point what is "interfering" with what; we chould perhaps say
"interference between strong and Primakoff amplitudes (Int)" or add a
sentence prior to this sentence that says "The Primakoff and strong
interactions amplitudes will interfere, and that interference must be
properly taken into account when calculating the differential cross
sections."

25. A few sentences farther on, we write "photo-produced". Since we have
not broken up the word anywhere else, we should simply write
"photoproduced". In the same sentence, we should say "on" rather than
"of", and can avoid the awkward "$\pi^0$s" by just saying either "pions"
or "neutral pions". Thus, I would suggest: "The FSI effects on the
photoproduced pions, as well as the photon shadowing effect in nucleare
matter, need to..." At the end of that same sentence, we have several
problems, so I would suggest that we write "...an extraction of the
Primakoff amplitude with an uncertainly of better than one percent, and,
therefore, the decay width." Thus, the whole sentence now reads: "The
FSI effects for the photoproduced pions, as well as the photon shadowing
effect in nuclear matter, need to be accurately included in the cross
section calculations to provide an extraction of the Primakoff amplitude
with an uncertainly of better than one percent, and, therefore, the
decay width."

26. Column two, last paragraph, second sentence: use dashes to separate
the parameters. Also, I would suggest rewording slightly to make things
clearer: "In the fitting process, four parameters --- ...--- were varied
to calculate the magnitude..."

27. The next sentence may confuse the reader as it stands. I would
suggest "Multiple independent analyses of the experimental data by
groups within the PrimEx collabration yielded the weighted averages
presented in Table I for 12C and 208Pb." 

PAGE FOUR

First column -- 

28. First line: Should read "...quoted total systematic uncertainty is
the quadratic sum of all estimated uncertainties in this experiment."

29. Next sentence: "The systematic uncertainties.."

30. Second sentence: "...well-known processes..." and "...with the
theoretical predictions..."

31. Last sentence: "Our result, with a total experimental uncertainty of
2.8\%, is the most precise measurement of the ... to date, being 2.5
times more precise than the current average value quoted in the PDG [3]
for this important fundamental quantity."

Second column ---

32. Third sentence: "To assess the effects of chiral corrections to the
anomaly, a measurement with a precision more than a factor of two better
than the current measurement is required."


-----Original Message-----
From: primex-bounces at jlab.org [mailto:primex-bounces at jlab.org] On Behalf
Of Ashot Gasparian
Sent: Friday, July 09, 2010 9:45 AM
To: primex at jlab.org
Subject: [Primex] the latest version of the prl paper


   Dear PrimEx Collaborators,

   The latest version of the PRL draft is in the attachment.
   It includes the most of suggestions done before yesterday
   (Thursday) evening and it is formatted to fit 4 pages (it
   was not an easy work).

   This version does not include suggestions and comments received
   from this morning (Friday). Many of them are very valuable
   and we will try to implement them in the text.

   Please keep commenting on the draft before Monday's Collaboration
   meeting, where we intend to finalize the most part of the paper.

   Regards,
   Ashot


.............................................................
Ashot Gasparian                    Phone:(336)285-2112 (NC A&T)
Professor of Physics
Physics Department                       (757)-269-7914 JLab
NC A&T State University              Fax:(757)-269-6273 JLab
Greensboro, NC 27411               email: gasparan at jlab.org
.............................................................