First Fits

[Matthew Shepherd <mashephe@indiana.edu>]

Hi all,

As I mentioned last week at the software meeting, Mihajlo and I are  
working amplitude analysis in all-neutral channels.  Mihajlo has  
written some reconstruction/analysis code for the eta-pi channel.   
We've generated a toy data set with interfering a0(980) -> eta pi and  
a2(1320) -> eta pi resonances using very simple two Breit-Wigner  
model for now.  This gets run through hit level MC where Mihajlo does  
reconstruction using the full BCAL and FCAL algorithms along with  
event selection.  Using an independent phase-space-like MC sample to  
model acceptance we then do the partial wave decomposition in bins of  
eta pi mass fitting for 5 waves (P and D have different m projections  
that are added together in the plots below).

Attached is the result of the first fit to the "data" -- hot of the  
press.  Of course, there are many studies to do, but already we can  
see the fitter pulls out the two dominant waves.  You can see other  
things too, like what appears to be some leakage into the D wave  
under the a0.  We'll be paying particular attention to leakage into  
the exotic P waves, especially when we start to tinker with how well  
we understand, for example, the BCAL/FCAL gap.  We also want to focus  
on the error bars because these are can reflect ambiguity or  
correlations between wave amplitudes as a result of imperfect  
acceptance.  See you all later in the week.

Cheers,

Matt

first_fit.pdf