[Clascomment] Fwd: Re: OPT-IN: Tensor Correlations Measured in 3He(e,e′ pp)n

[Larry Weinstein]

Dear Dan,

As ever, I am awed by your attention to detail.  My responses follow
your comments.  The latest version will be posted tomorrow.  I need to
work on the tensor correlation importance, among other items.

- Larry

Daniel Carman wrote:
>  						July 10, 2010
>
>
>  Dear Larry et al.,
>
>  I have read through the draft of your correlations paper. To be honest,
>  I do not think that this paper meets the threshold for \"general interest\"
>  needed for acceptance and publication in Phys. Rev. Lett. I just don\'t
>  think that the discussion really makes a clear statement of what is so
>  important or interesting here. The big conclusion seems to be that
>  tensor correlations are important to describe this data. But you have
>  not said anything general enough to tell me why anyone should care about
>  this finding. Also, while th first 2.5 pages were readable and
>  understandable, I found the second half of the paper to be to \"jargony\"
>  and specialized for me to follow.
>
>  Anyway, this is just my opinion. Take it for what it\'s worth. I will
>  support your journal submission decision. My specific comments on the
>  manuscript (dated July 2, 2010) are given below. Let me know if you have
>  any questions.
>
>
>  				Regards,
>
>  				Daniel
>
>  *************************************************************************
>  General.
>     - I recommend you use c=1 units throughout this paper. Your usage of
>       units is not consistent.
>
Actually, I used GeV^2 for Q^2 and GeV/c for the magnitude of 3-momentum
consistently.
>  Page 1.
>     Right Column.
>       Paragraph 2.
>         Line 8. Use \"$^{12}$C\".
>
I deleted the line to save space and because the information is repeated
later.
>       Paragraph 3.
>         Line 3. I find this sentence awkwardly written. How about \"... of
>           other effects, including Final State Interactions (FSI) and
>           two-body currents such as meson exchange currents (MEC) [14], which
>           add coherently to the correlation signal.\".
>         Line 7. Use \"two-body current\".
>         Line 8. Use \"... 2m\\omega>   1$, where $Q^2$ ...\".
>         Line 9. Use \"... transfer, respectively.\".
>
Done
>  Page 2.
>     Left Column.
>       Paragraph 2.
>         Line 3. Use \"5-cm-long\".
>
I deleted 'long'
>       Paragraph 3.
>         Line 1. I prefer \"CLAS uses a ...\".
>         Line 1. Use \"in-bending\".
>
Done
>         Line 5. The statement that momentum coverage extends down to
>           0.25 GeV for protons is kind of misleading/confusing. It extends
>           down to a value where the protons make it through CLAS to the
>           TOF (above ADC threshold or perhaps trigger threshold) and where
>           we have confidence that we can account for energy loss corrections.
>           So, your value is somewhat arbitraryly chosen, but you make it
>           sound like a true threshold for CLAS, which it is probably not.
>
It was true for our target and magnetic field combination.  I moved the
sentence to later in the paragraph so it refers to this experiment and
is not a general statement about CLAS.
>         Line 14. You say that you relied on comparing your extracted elastic
>           cross section to the world\'s data. I think it is appropriate to
>           state quantitatively the level of this agreement. Also, comparison
>           of elastic cross sections is not fully appropriate to tune up your
>           acceptance/efficiency corrections for CLAS because your multi-
>           particle final state includes particle correlations that affect
>           reconstruction and trigger efficiency. These effects are not in
>           the elastic channel. Comments?
>
The particle correlations did not significantly affect the efficiency
because our particles were, if anything, anti-correlated in space.  The
level of agreement is reflected in the systematic uncertainties.
>       Paragraph 4.
>         Line 7. You state that Fig. 1 (right) shows the missing mass
>           resolution. You have said nothing about the resolution as no
>           fit is shown.
>
changed to 'missing mass cut.'
>       Fig. 1 caption.
>         Line 1. Use \"vs.\".
>
OK
>     Right Column.
>       Fig. 2 caption.
>         Line 1. This is really not a \"Dalitz plot\".
>
Put "Dalitz plot" in quotes
>         Line 1. Use \"vs.\" instead of \"versus\" for consistency.
>
OK
>       Paragraph 1.
>         Line 6. Your statement about \"upper right half of the plot\" is
>           confusing. Where exactly are we supposed to be looking? I think
>           you should be explicit and say events for which $T_{p1}/\\omega
>           + $T_{p2}/\\omega>   1$.
>
OK
>         Line 9. The sentence \"There are three peaks at the three corners
>           ... where two nucleons each have less than 20% ...\" is kind of
>           (sort of) speculative without seeing the correlation with the
>           $T_n/\\omega$ axis.
>
No, the T_n/omega axis runs at 45 degrees from the lower left to the
upper right.
>       Paragraph 2.
>         Line 1. Use \"We then looked at the opening angle ...\".
>         Line 6. Use \"... simulation that assumes three-body ...\".
>
I guess you paid more attention in English class than I did.  I thought
I was pretty good at this stuff.  Done.
>       Paragraph 3.
>         Line 5. The cut on p_perp<   0.3 GeV seems kind of arbitrary. Any
>           motivation to share for this choice?
>
It's a tradeoff between more statistics (higher value of cut) and
cleaner data (lower cutoff).  The data did not change significantly as
we increased the cutoff from .1 to .2 to 0.3.  We are running out of
space to describe things.
>         Line 7. The sentence \"These paired nucleons are distributed almost
>           isotropically in angle ...\" is unclear. You just said that the
>           paired nucleons are peaked at 180 deg, as seen in Fig. 2 (right).
>           What am I missing here?
>
Corrected to read 'The angle between $\vec q$ and the momentum of the
neutron (of the $pn$ pair) is distributed almost isotropically.'
>  Page 3.
>     Left Column.
>       Paragraph 2.
>         Line 3. Use \"... in Figure 3, along with ...\".
>
OK
>         Line 9. You state a systematic of 15%. I would like you to add a
>           bit more here and at least state what the major/dominant source
>           of systematic were and their contribution to the total uncertainty?
>
The systematic uncertainty is 15\%, primarily due to the uncertainty in
the low
momentum proton detection efficiency.
>       Fig. 3 caption.
>         Line 4. Provide a reference in the caption to the Golak work.
>
OK.  And Laget also, now that his curves are included also.
>       Paragraph 3.
>         Line 1. I found the first sentence confusing because I did not know
>           if you were trying to discuss both the pp AND pn pairs or just
>           the pn pairs. I believe you are trying to talk about the pn pairs.
>           Thus I would suggest \"For the $pn$ pairs, the $p_{rel}$ ...
>           0.7 GeV. The associated $p_{tot}$ distribution for the $pn$
>           pairs rises ...\".
>
I moved the statement that they are similar to the beginning of the
paragraph:
"The $pp$ and $pn$ pair momentum distributions are similar."

>     Right Column.
>       Paragraph 3.
>         This was the point in the paper where I think things started to
>         get very \"for experts only\" and I started to get lost.
>         Line 1. You start to discuss the calculation by Laget, but you do
>           not show the results of his calculation anywhere.  Also, I don\'t
>           think describing the Laget calculation as a \"diagrammatic approach\"
>           really tells me anything about this calculation. I have no idea
>           what to make of this.
>         Line 6. The two sentences beginning \"The $pp$ pair momentum distributions
>           ... in as $p_{tot}$ increases.\" mean nothing to me. I have no
>           idea what you are trying to say.
>         Line 12. Also, you do not make it clear what \"large\" means when
>           discussing the level of three-body contributions in the Laget
>           calculation. What does \"large\" mean relative to the full cross
>           section and the two-body contribution?
>
Thank you for being so specific.  I deleted some of the confusing (and
relatively unimportant) details from the discussion of Laget's
calculation.  I also added his plots to the figure so you can see what
'large' means.
>       Paragraph 4.
>         Line 1. You state a ratio of pp to pn pair cross sections of 1 to 4.
>           I don\'t see how this follows from Fig. 3. It looks like 1 to 2 or
>           1 to 2.5. How did you determine this value?
>
by integrating the cross section over either p_rel or p_tot
>       Paragraph 5.
>         Line 7. What does \"relatively low $p_{tot}$\" mean?
>
clarified (<0.15 GeV/c)
>       Paragraph 6.
>         Line 8. I suggest \"... increases to $sim$0.4 to 0.6 for ...\". Your
>           value of 0.5 disagrees with Fig. 4.
>
OK
>         Line 9. The sentence \"The ratio rises much faster than the ...
>           calculated from the bound state wavefunction.\". I have no idea
>           what this means.
>
clarified
>         Line 13. Use \"... 0.4 - 0.6$ at large ...\".
>
ok
>
>  Page 4.
>     Fig. 4 caption.
>       Line 3. Provide a reference in the caption to the Golak paper.
>
OK
>       Line 5. What is the dashed calculation here? I have no idea what this
>         means based on what you have provided.
>
clarified (I hope)
>     Left column.
>       Paragraph 2.
>         Line 1. Why should I care about tensor correlations? You need to
>           provide some appropriate discussion on this point.
>         Line 2. \"At low $p_{tot}$, the $pp$ pairs are in an $s$-state ...\".
>           Based on what? Is this an assumption or do you have something
>           to back this up?
>         Line 4. \"Due to the tensor interaction, the $pn$ pair does not
>           have this minimum.\". I have no idea what this means. Is this
>           a general feature that can be explained or some model-dependent
>           point?
>
I have clarified the discussion of the wave functions.  This is all
backed up by the references.
>         Line 9. Again, you use the very loose terminology \"large contributiom\".
>           See my earlier comment on this point.
>
His curve is now included in the figure so large can be judged.
>       Paragraph 3.
>         I found this entire paragraph to be \"loosely\" written. I am not
>         sure that it made a clear, crisp point.
>         Line 4. Use \"... only one other nucleon.\".
>
OK
>         Line 16. Provide a reference to the Laget prediction.
>
Laget prediction deleted.
>     Right column.
>       Paragraph 1.
>         Line 10. Use \"... approximately 0.6 at ...\".
>
No, the average is about 0.5 and the last two points (at 0.6) have large
uncertainties.
>         Last sentence. Again, I am not sure why this is important.
>
>  References.
>    - Why do you include a preprint number for published papers? I don\'t
>      think this is appropriate.
>
done
>    - Refs. [12], [26], [28] are not in standard format. Also, get rid of
>      the URL.
>
done
>    - With Ref. [12] you list a collaboration. You do not do this consistently
>      for the other papers, notably the CLAS Collaboration papers.
>
done
>    - Ref.[19] should be \"B.A. Mecking et al.\".
>
I don't know how to make bibtex fix that.  Sigh.

-- 
				Sincerely,
				Larry

-----------------------------------------------------------
Lawrence Weinstein
University Professor
Physics Department
Old Dominion University
Norfolk, VA 23529
757 683 5803
757 683 3038 (fax)
weinstein at odu.edu
http://www.lions.odu.edu/~lweinste/