[d2n-analysis-talk] A1 Paper: PDF Models for Delta q/q Plot

[David Flay]

Hi all,

I have been looking into various combinations of polarized and unpolarized
PDF models for use in our Delta q/q plot in the A1 paper.  The attached
file shows a few combinations of polarized PDF models with the unpolarized
PDF model CJ12 compared to not using CJ12 (for example, with LSS, the
other option is that we use LSS for the unpolarized component).  I am
plotting things up to x = 0.8, as in some cases these combinations yield
Delta q/q > 1, which still occurs for LSS and Avakian parameterizations at
this x value; this seems to be due to how CJ12 falls off faster than say,
LSS, BSS and Avakian in their unpolarized forms.  For all models, Q2 = 4
GeV^2.

Perhaps we can do is use the following combinations for the paper:

1. LSS (Delta q), CJ12 (q)
2. Avakian (Delta q), CJ12 (q)
3. Stat (Delta q), Stat (q)

This way, things are consistent in the sense that we have done our
analysis using CJ12, and that same model also shows up in the plots; we
keep the Stat model on its own, since that fit is done using both
unpolarized and polarized data.

In short, we are consistent with Avakian in terms of the shape when we
consider CJ12 for the unpolarized component.

Also attached is a sample plot of Delta q/q with our data.  We can see
here how the models for Delta u/u go larger than one, and is perhaps a
reason for not showing our up quark results and to wait for the proton
data from CLAS.

What are your thoughts?

Best regards,

David

-------------------------------------------------
David Flay
Physics Department
Temple University
Philadelphia, PA 19122

office: Barton Hall, BA319
phone: (215) 204-1331

e-mail: flay at jlab.org
            flay at temple.edu

website: http://www.jlab.org/~flay
              http://quarks.temple.edu
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