[d2n-analysis-talk] Neutron extraction for A1

[Brad Sawatzky]

Hi Diana, Gregg,

Any chance you have heard from Wally on the 3He to neutron corrections
discussed below?

My notes from June suggest that he might have something for us around
September.  Odds are this fell to the bottom of his todo list, but I'd
like to follow up on it and get a feel for the status.

Diana's email from June 10 suggests there may be an email from Wally
with some comments on the more general, x-dependent method he and
Kulagin published in 2008  (second bullet in Diana's email below).
If so, can that note be cc'd to the list for reference?

-- Brad

On Wed, 15 Jun 2011, Brad Sawatzky wrote:

> Just a couple comments on issues to keep in mind.
> 
> Note that we'll want to have the information available to correct the
> g_1(x,Q2), g_2(x,Q2) points individually, _and_ to be able to correct
> the d2(Q2) term as a 'unit'.  That is we'll want to be able to apply a
> correction to the already-integrated d2 matrix element, rather than
> correct the individual integrand points prior to integration.
> 
> (We'll probably do it both ways, but the latter method should result in
> a smaller systematic uncertainty for the final d2n value.)
> 
> -- Brad
> 
> On Fri, 10 Jun 2011, Diana Parno wrote:
> 
> > Wally Melnitchouk and I met yesterday afternoon and had a very  
> > productive discussion about going from 3He to the neutron. Here's the  
> > executive summary:
> > 
> > - The Bissey et al method (which I presented in last week's analysis  
> > meeting) assumes no x-dependence (so, it's not quite as "complete" as  
> > the title describes!). This is probably safe for our DIS points but  
> > definitely not for our resonance points.
> > 
> > - Wally recommends the more general, x-dependent method in Kulagin and  
> > Melnitchouk, PRC78 065203 (2008). Unfortunately, they've only worked  
> > out this method for g_1 and g_2 on the neutron, not on the  
> > asymmetries. He thinks that the extension to A_1 and A_2 would be  
> > relatively straightforward and a useful problem, and predicts that he  
> > should have something for us on the general time scale of three months  
> > (see email). He's excited at the prospect of experimental interest in  
> > the method described in the 2008 paper. From our end, I think a few  
> > months is quite reasonable and will give us time to pursue the 5.9-GeV  
> > dataset, pair-production corrections, radiative corrections, etc.
> > 
> > - He agrees with my worry about Bissey et al's assumption that A2 is  
> > close to zero, but we think that (for a first look at the DIS data  
> > points), their equation should be very easily extensible to g1/F1  
> > without having to make that assumption. I think the math on that is  
> > relatively simple and I'll work on it next week.
> > 
> > - He doesn't think that anti-shadowing is a big deal for our low-x  
> > point -- probably a few percent. On the other hand, we're worrying  
> > about a few-percent EMC effect, so perhaps it's worth some study. His  
> > own work includes the delta isobar but not shadowing/anti-shadowing.
> > 
> > Brad, Matt, and Dave: I enjoyed seeing you at the Hall A meeting! Hope  
> > we'll cross paths in person some time again soon. It was a very  
> > productive and interesting couple of days.
> > 
> > Enjoy your weekends,
> > Diana
-- 
Brad Sawatzky, PhD <brads at jlab.org>  -<>-  Jefferson Lab / Hall C / C111
Ph: 757-269-5947  -<>-  Fax: 757-269-5235  -<>- Pager: brads-page at jlab.org
The most exciting phrase to hear in science, the one that heralds new
  discoveries, is not "Eureka!" but "That's funny..."   -- Isaac Asimov