[G14_run] pi- p systematics

[Reinhard Schumacher]

Hi g14 folks,

We have no meeting this week, but I wanted to mention something before 
we all head off to eat turkey.

At the last meeting we looked at some work by Tsuneo in which he studied 
shifts in E as a fraction deviation rather than an additive deviation 
from the "best" values.

In Dao's thesis, he had his systematic studies in terms of additive 
uncertainties.  However, he also reported an equivalent multiplicative 
(i.e. fractional) systematic uncertainty.  This is given on page 134/135 
of the thesis.  This can be compared with the bottom-line result done by 
others.

He and I also had some quick communication about why an additive 
uncertainty might be more instructive to use than a multiplicative one. 
In an analysis there is always some remaining background from target 
material (which has zero asymmetry) and Delta production where an extra 
pion is missing (and might have non-zero asymmetry). In fact, there is 
evidence that this latter type of background has POSITIVE asymmetry 
which would cause the ppim E asymmetry to shift up. It was pointed out 
by one of the thesis reviewers.  You can see in the top plots of Figure 
4.17 (page 74) there are several black points that are POSITIVE. This 
can't happen if the Delta production has zero asymmetry. I.e., dilution 
can not push negative data points to positive.  In this situation it 
does not help to use a multiplicative rescaling.

We can talk about this at length next week.

Happy Thanksgiving holiday,
Reinhard