[Clascomment] answers to your comments on the dvcs prd - eg1dvcs

Wed Jan 14 07:37:19 EST 2015

Dear Michel and dear all,

we modified the paper accordingly to our agreement. You can find it at the
link:

http://www.lnf.infn.it/~pisanos/dvcs/prd/prd_dvcs_eg1dvcs_author_check.pdf

Let us know if we can now proceed to the final author check.

Best regards,

silvia

On 13 January 2015 at 17:30, GUIDAL Michel (57321) <guidal at ipno.in2p3.fr>
wrote:

> I could agree to something like that. My intention is not
> to "erase" the CFF notation that Michel advocates. But my intention
> is certainly to keep alive the notation that I advocate (especially
> when it is my work which is quoted !).
> Just for completeness/addition, I am about to release,
> with my (former) grad. student Marie, a paper
> on the simultaneous fit of DVCS and TCS (pseudo-)data.
> And in TCS, what one fits is the _conjugate_ of the CFF
> to the current Eq.8, which would mean that you don't have the same
> CFFs, according to the current eq.8, between DVCS and TCS.
> With the definition that I advocate (and that I will continue to use
> in any case), I can certainly speak of the "same" CFFs: this is
> flexible, convenient and esthetic.
> Amities,
>
> Michel
>
>
> On Tue, 13 Jan 2015, Silvia Niccolai wrote:
>
>  Dear all,
>> I have a proposal to solve this perennial issue of the definition of the
>> CFFs.
>> We could keep in the introduction the CFF definition that is in the
>> current version, but in the section devoted to the CFFs extraction we could
>> specify the definition adopted in the fit-based extraction procedure by
>> Michel et al.
>> This way all would be consistent and clearly stated.
>> What do you guys think?
>> Best regards
>> Silvia
>>
>>
>> Sent from my iPhone
>>
>>  On 13 Jan 2015, at 16:17, GUIDAL Michel (57321) <guidal at ipno.in2p3.fr>
>>> wrote:
>>>
>>> Dear all,
>>>
>>> I went quickly through the latest vesion of the article:
>>>
>>> http://www.lnf.infn.it/~pisanos/dvcs/prd/prd_dvcs_
>>> eg1dvcs_author_check.pdf
>>>
>>> I notice that, under the comment/pressure of only one person, the CFF
>>> definition has been changed (Eqs.9 and 10).
>>>
>>> 1/I think that the least that should be done is to mention that
>>> some people use other definitions, especially when this is
>>> the work of these particular people which is particularly used in the
>>> paper. I remind that the latest review on the field (Rept.Prog.Phys. 76 (2013)
>>> 066202, M. Guidal, M. Vanderhaeghen and H. Moutarde, i.e. signed
>>> by 3 authors which, I dare to think, are not beginners in the field) use
>>> the particular definition that was originally used in this paper.
>>>
>>> 2/this absolutely useless and unnecessary change leads now
>>> to inconsistencies in the text:
>>>
>>> l.1172:"In recent years, various groups have developed and applied
>>> different procedures to extract Compton Form Factors
>>> from DVCS observables". With the current definition of CFFs, this
>>> is not true, nobody has tried to extract: "Int(GPD(x,+/-xi,t)/(x+/-xi+
>>> ieps)dx".
>>>
>>> l.1176:"the CFFs are almost-free parameters". With the current
>>> definition, this is not true.
>>>
>>> l.1187:"to extract the Compton Form Factors". Same as above.
>>>
>>> l.1197:"Given that the size of the error bars reflects the sensitivity
>>> of the combination of observables to each CFF". With the current definition
>>> of CFF, this is not true because the different observables have
>>> different sensitivities to the imaginary and real parts of CFFs
>>> (current definitoin ;-) ).
>>>
>>> l.1214:"both sets of CFFs are compatible". This is not correct
>>> with the cirrent defintin of CFFs.
>>>
>>> And the vertical axis of Fig.25 is very ambiguous. Please, let's
>>> avoid the horrible: "-Im(Htilde)/PI..."
>>>
>>> And I have probably forgotten some other instances.
>>>
>>> 3/there is absolutely no doubt in my mind that the original notation
>>> used in this paper was the most practical, convenient and esthetic
>>> and I don't understand why one person managed to change the notation.
>>> I certainly recommend to go back to the original one. Especially that
>>> the next paper to come in the subject, the DVCS x-sections by HS Jo et al.,
>>> will use that paricular notation.
>>>
>>> Amities,
>>>
>>> Michel
>>>
>>>  On Tue, 13 Jan 2015, Silvia Pisano wrote:
>>>>
>>>> Dear Michel,
>>>> thanks a lot for your useful comments. We implemented most of them (and
>>>> did
>>>> not report about the accepted ones, since we agree on them).
>>>> Below, you can find our answers on the points that need a more detailed
>>>> discussion.
>>>> Best regards,
>>>> Angela, Erin, Silvias
>>>> -----------------------------------------------------------
>>>> - "Eqs 1 and 2 could (should?) be in line within the text, and there is
>>>> a
>>>> minus sign missing in Eq 1."
>>>> Thanks for noting the sign, you are right! As to the positioning of the
>>>> equations, we preferred to leave them as they are, to give the right
>>>> resonance to the quantities introduced. We also slightly modified this
>>>> part
>>>> following some suggestions from Volker.
>>>> - "L73-74: not quite correct. “The transverse part of t is the squared
>>>> Fourier conjugate of the transverse ….”.
>>>> Yes, you are right. We corrected it.
>>>> - "Eq8: to be consistent with Eq 6, is not there a factor –pi missing ?"
>>>> Yes, we included it.
>>>> - "L106: “With a finite number of measurements, a model input is
>>>> necessary
>>>> to deconvolute…” (meaning that with an infinite number of integrals
>>>> along x,
>>>> there are, or could be,  mathematical ways to get the x-dependence;
>>>> this may
>>>> be compared to medical imaging reconstituting 3D images from 2D
>>>> measurements)"
>>>> We preferred to leave it as it is, since we will always have a finite
>>>> number
>>>> of measurements only, and don't wanna be misleading with too many
>>>> details.
>>>> "L135: HERMES statistics on TSA are comparable to exploratory CLAS (see
>>>> Fig.
>>>> 22). I would write: “….was also performed. The statistics obtained in
>>>> measurements [13,14] do not allow for a 4-dimensional binning of the
>>>> data”.
>>>> We rephrased that paragraph, and the presentation of the previous
>>>> measurements has been reordered.
>>>> - "L 187-188: F1 and F2 already defined. Put a full stop at the end of
>>>> Eq
>>>> 16, skip “where…factors” and write “Due to the relative values of the
>>>> proton
>>>> form factors F1 and F2,….”"
>>>> Thanks, it is way better now.
>>>> - "L190-191: this is not quite correct, and we had that discussion
>>>> before
>>>> for the PRL and checks were made with VGG. The contributions of H and
>>>> H_tilde to A_UL are quite comparable. It is misleading to say that the
>>>> latter is dominant and the former minor. Please find another
>>>> formulation."
>>>> Ok, we modified the text explaining better why there is a comparable
>>>> sensitivity to ImH and ImHtilde.
>>>> - "Section III: may be worth adding towards the end the beam helicity
>>>> flip
>>>> frequency and a typical target polarization reversal frequency."
>>>> While we know that the helicity change is the usual one - i.e. 30 Hz -
>>>> it is
>>>> hard to define a typical frequency in changing the target polarization,
>>>> since the changes were not regular at all. We preferred then not to
>>>> mention
>>>> this information, not to create "asymmetry" among the two polarization
>>>> information.
>>>> - "About combining results from parts A and B, it would be instructive
>>>> (and
>>>> maybe necessary) to add what is the expected beam energy dependence of
>>>> the 3
>>>> observables from a given model (say VGG), for fixed xB, Q2, t. It is not
>>>> enough, as is done later, to show that the bin centers are nearly the
>>>> same."
>>>> We did some studies through the VGG model, the results of which can be
>>>> found
>>>> here:
>>>> http://www.lnf.infn.it/~pisanos/dvcs/prd/coll_wide_review/ebeam_test/
>>>> The two curves are the -t dependence of the three asymmetries in our 5
>>>> (Q2,
>>>> xb) bins for the two beam energies  (blue line is partA, red partB).
>>>> Since
>>>> the difference is very small it is well beyond our statistical
>>>> precision.
>>>> - "Table III: same number of significant digits everywhere ?"
>>>> To the best of our knowledge the significant figures are correct as is.
>>>> For
>>>> statistical errors one usually retains only the first non-zero digit
>>>> unless
>>>> the error is small (e.g. 0.015) and then it is common practice to keep
>>>> two
>>>> digits. For these reasons all the PbPt and one of the Pb errors have two
>>>> digits, while the other ones have been rounded to one.
>>>> - "L853: $R_Acc, 1.3\times R_Acc, 0.7\times R_Acc$"
>>>> We explained it in words, to make the sentence more readable.
>>>> - "L891 and others: we call GK (from the original GPD parameterization)
>>>> a
>>>> calculation of DVCS observables made by KMS (and for this paper by MS).
>>>> Although this is a bit heavier notation, why not replacing GK by GK-KMS
>>>> ? GK
>>>> did not calculate DVCS, and it would be fair to our collaborators on
>>>> this."
>>>> Unfortunately, we cannot change it anymore since we used the same
>>>> notation
>>>> for the PRL, and we need to be consistent among the two papers.
>>>> - "Fig.26 caption: is not it -ImH/pi and - ImH_tilde/pi which are
>>>> plotted?
>>>> If yes, should be explicit in the caption."
>>>> The quantities that we plot in the figure are the actual imaginary
>>>> parts of
>>>> the CFFs, because we keep into account the -pi factors.
>>>> - "Table V: strictly speaking, TSA, its errors and c (DSA and other c)
>>>> should have the same number of significant digits (4). I would leave it
>>>> as
>>>> is, but make sure it is the case in the CLAS data base."
>>>> We adopted the convention to present all the results with 3 sig figures,
>>>> however being the TTSA correction so small we decided to report with 4
>>>> sig
>>>> figures to avoid zero values.
>>>> Thanks again!
>>>>
>>>
>>> --
>>> ***
>>> Michel GUIDAL
>>> Institut de Physique Nucleaire
>>> Bat 100 - M019
>>> 91406 ORSAY Cedex
>>> Tel: (33) 01 69 15 73 21
>>> Fax: (33) 01 69 15 64 70
>>> E-mail: guidal at ipno.in2p3.fr
>>> ***
>>>
>>
>>
> --
> ***
> Michel GUIDAL
> Institut de Physique Nucleaire
> Bat 100 - M019
> 91406 ORSAY Cedex
> Tel: (33) 01 69 15 73 21
> Fax: (33) 01 69 15 64 70
> E-mail: guidal at ipno.in2p3.fr
> ***
>

-- 
 "Life was just chemistry,
  and chemistry was just physics." - Jonah Lehrer
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