[Deeppwg] NSTAR proceedings

[Silvia Niccolai]

Hello Michel/Daria,
the main problem I see in showing those two asymmetries side by side is 
that it is not clear to me, and it is not explained in the text, how they 
are defined. Both asymmetries needs various correcting factors 
(polarizations, backgrounds, and for the TSA there is the dilution factor) 
that I am not sure are at this stage included in Daria's plots. So, the 
magnitude of the real asymmetries could be different from what is shown. 
besides, as you pointed out, the different choice of fitting function for 
the two observables can be misleading for whoever may end up just looking 
at the value of the p0 parameter in the fit window...
If we want to keep the two observables, they were they are defined should 
be clearly stated, and the choice of fitting function should also be 
motivated.
Best regards,
Silvia


On Tue, 1 Dec 2015, GUIDAL Michel (57321) wrote:

> Hi Daria,
>
> Some more comments in addition to Volker's and Silvia's:
>
> *abstract, l.3:
> "Data from both proton and neutron targets is required for an extraction of 
> all accesible GPDs...". It is not clear to me what are the "accessible GPDs" 
> ? What are the "non-accessible GPDs" ?
>
> *introduction, par.1, l.1: "The most complete information..." might be too 
> strong, there are probably things on nucleon structure which cannot
> be accessed through GTMDs. "A wealth of information..." or something like 
> that to be cautious.
>
> *l-7/8: two times "the".
>
> *par.2, l.11: "extraction of the real parts of GPDs...". Silvia pointed it at 
> some other place above, here it comes again: GPDs are real.
> Also, I wouldn't say that "cross-sections and double-spin asymmetries allow 
> the extraction of the real part...", they are "sensitive to".
> For the true "extraction", one needs more than these 2 observables.
>
> *par.3, l.4: "the imaginary part of the GPD E". Again, GPDs are real.
>
> *l.5: "acesSible". Also, I would remove the "however", I don't see any
> contradiction with the fact that E is the least known.
>
> *p.2, 3 lines below eq.1. "This paper..." is not very nice. "These
> proceedings", "This article",...
>
> *section 2, par.1, l.6: "electRon".
>
> *l.8: "scintillator wall". It might be strange to call our IC made of
> PbWO4 crystals "scintillator wall". "Scintillators" refer to something
> else in general.
>
> *par.2, l.7: "the recoil electron". A bit strange. "scattered electron" 
> rather ?
>
> *l.13: "stacettering" !!!
>
> *l.14: "W>2 GeV/c2" Sometimes you use the "c" and sometimes not
> (line below: "Q2>1 GeV2"); you probably have to choose and stick to one 
> notation.
>
> *l.16: "factorisation...into a hard-scattering and a soft-scattering part 
> applies". You never introduced those "hard" and "soft parts". It seems
> to come out of the blue...
>
> *last sentence of par.2: "(to estimate which the same particle identification 
> and distribution cuts were applied to 14ND3 data)"
> sounds bizarre.
>
> *par.3, l.1: "traget".
>
> *Fig.2: I am not shocked by the target asymmetry. Maybe, there is
> no signal indeed but still this is information. I have no
> problem to leave it but no problem as well to remove it. Actually,
> the overall question is what is allowed to be released according to the CLAS 
> rules ?
> By the way, in the caption, why do you fit the BSA and the TSA by 2 different 
> functions ?
>
> *p.5, bibliography: "[5]:... PRL 99". ->"Phys.Rv.Lett."
> [6]: instead of "private communication", you can probably refer
> to the original CLAS proposal. This is true that I/we should publish on 
> n-DVCS some day.
>
> Amities,
>
> Michel
>
> ***
> Michel GUIDAL
> Institut de Physique Nucleaire
> Bat 100 - M130
> 91406 ORSAY Cedex
> Tel: (33) 01 69 15 73 21
> Fax: (33) 01 69 15 64 70
> E-mail: guidal at ipno.in2p3.fr
> ***
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