[d2n-analysis-talk] Update on Neutron Extraction

[Diana Parno]

Hi all,

I want to pass along Wally's preliminary results from our problem.  
He's finished what he thinks is the hard part -- the smearing  
functions. Here's what he writes:

> Here are some preliminary results from my He3 structure function
> calculations.  I reprogrammed some of my troublesome codes in Fortran,
> and have succeeded in completing the main part of the calculation --
> that of the nucleon "smearing functions" (nucleon momentum  
> distributions)
> in He3.  (The results are preliminary because I am using a smaller  
> number
> of grid points in the integrations than I would in the final analysis,
> in order to speed up the calculations.)
>
> The figures show A1 and xg1 of the neutron and He3 with various
> approximations.  Note that the He3 asymmetries have been scaled by the
> ratio F1(He3)/F1(n) in order to display them on the same scale as the
> neutron.  Without this factor the He3 asymmetry is ~3-5 times smaller
> than the neutron asymmetry.  (No such factor is needed for the xg1
> structure function comparisons.)
>
> I haven't yet compared with the Bissey et al. ansatz, but this will
> be straightforward.


All of this uses the effective polarization approximation (treating  
the polarization of each nucleon as constant in x). "No p" means that  
the effective polarization of the proton is assumed to be zero;  
similarly, "no g2" means that the g2 contribution has been turned off.

The last attachment is a plot I prepared that shows the approximate  
scaling factor for the He3 asymmetries in Wally's plots:

> The ratio F1(He3)/F1(n) is roughly equal to 2*F1(p)/F1(n) + 1,
> neglecting nuclear effects (which is good to a few percent up to
> x ~ 0.7).  You can use your F2 and R parametrizations to see how
> this looks vs. x ...

The plot also uses our kinematics (i.e. x and Q^2 in each bin). I drew  
a vertical line at x=0.7; for higher x values, the nuclear effects are  
no longer roughly negligible.

I'm planning to meet Wally and (hopefully!) Zein-Eddine tomorrow for  
lunch to discuss this further. (The meeting place is the very cutely  
named h-bar on the first floor of the physics building, at 12:20.)

Cheers,
Diana

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