[Clas12_first_exp] [EXTERNAL] RE:PAC48 slides

[SABATIE Franck]

I would be careful with giving hand-waving  arguments in front of that PAC, considering the comments from the last PAC session about the need for quantifying the impact of experiments and beam time.

Also:

It’s not just xB coverage that might be a problem. The t-coverage is also tricky, and to do it right, you would have to work with t/Q2 small.

One other thing to keep in mind, when :

- you cut off the series giving the subtraction constant to its first term and

- the first term is parameterized by a multi-pole (dipole or tripole) in t,

then, the shape of the pressure profile is essentially determined by modelling assumptions. The d1(0) factor is then only a simple normalization... The fitting range in t is also something that induces some systematic effects.

Bottomline: Markus knows all this, just be careful with this line of justification !

Good luck,
Franck

Le 24 sept. 2020 à 17:56, Francois-Xavier Girod <fxgirod at jlab.org> a écrit :


Concerning Kresimir's article raised by Franck
This is indeed one of the best arguments we have to argue for more data, as I already said during the meeting several times

Kresimir's criticism is that we use ad-hoc functional forms to perform global fits, and that these include poorly constrained extrapolations
Kresimir's approach, performing neural network fits, provide on of the safest most conservative estimation of the D term uncertainties
Our strategy is diametrically opposite to his
To justify our strategy we need the fullest possible coverage in xB (the variable that requires extrapolation)

Also note that combining RGA and RGK data we will be able to cleanly separate the linear interference term from the DVCS^2 contribution

Best regards
FX

On Thu, Sep 24, 2020 at 3:54 PM SABATIE Franck <Franck.Sabatie at cea.fr<mailto:Franck.Sabatie at cea.fr>> wrote:
Dear Latifa,

It looks good, once you incorporate the official DVCS plots in the presentation.

Note that there is a significant risk Markus Diehl will comment about the article from K. Kumericki (Nature volume 570, pages E1–E2 (2019)) in response to your own Nature article: a convincing answer needs to be ready since you put it as an highlight.

Kind regards,
Franck

________________________________
De : Clas12_first_exp [clas12_first_exp-bounces at jlab.org<mailto:clas12_first_exp-bounces at jlab.org>] de la part de Latifa Elouadrhiri [latifa at jlab.org<mailto:latifa at jlab.org>]
Envoyé : jeudi 24 septembre 2020 14:40
À : clas12_first_exp at jlab.org<mailto:clas12_first_exp at jlab.org>
Objet : [Clas12_first_exp] PAC48 slides

Dear All,

I have posted the PAC48 RGA talk at clas12 doc-db. I have implemented all the comments I received from the dry run.

I am waiting for the final DVCS slide from Maxime/FX
I am also waiting to see if there better graphs/results from MesonX.

Victor please check the summary see if I captured your comment correctly.

Please let me know if you have any last comment/suggestion.

Best regards,

Latifa
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