[d2n-analysis-talk] (no subject)

[David Flay]

Hi all,

I realized that my responses conerning the error bars on delta_u/u were
not sent to the d2n talk list.

There were questions concerning the size of the errors on the delta_u/u
values that we have extracted, compared to the other experiments.  I
should mention that the errors on our data (A1 and flavor) are statistical
only (I will update my slides to state this), and the size of those errors
are a result of how the statistical errors are calculated. If you look at
the equations (see the backup slides) when you compute the errors, the
error on delta_u/u is scaled down by 15, while delta_d/d is scaled by
4/15, multiplied by slightly different terms that are functions of d/u.

Furthermore, for the g1p/F1p data, I used Xiaochao's fit.  I also have the
errors corresponding to that fit, so I can do a systematic error study on
it.  For the d/u ratio, I used the CJ12 unpolarized PDF model (see the
last backup slide for plots showing these curves).   I had spoken with
Wally about the d/u data in that plot, and he mentioned that the CJ12 PDF
fits supercede the SLAC data from Phys. Lett. B 377, 11 (1996) in the
following way (quoting Wally):

[those data corresponding to d/u] extraction has in some respects been
superceded by the more recent CJ global analysis, which analyzes world
data and more systematically applies various nuclear and finite-Q^2
corrections in determining d/u.  See e.g. Owens et al., PRD 87, 094012
(2013).

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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