[d2n-analysis-talk] Neutron extraction for A1

[Brad Sawatzky]

Just a ping on the neutron extraction stuff.  I can volunteer to
follow-up locally if that would work best, but I don't want to step on
toes if this is in progress.

-- Brad

On Thu, 15 Sep 2011, Brad Sawatzky wrote:

> 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