[Clascomment] OPT-IN: Measurement of the Sigma Pi Photoproduction Line Shapes Near the Lambda(1405)

[Volker Burkert]

This is a very interesting paper of an analysis that tries to disentangle a very complex dynamical problem. 
 I want to congratulate everyone involved. I want to just make one comment. 

In my view the main result of the higher level analysis is the conclusion that the centroid of the Lambda(1405)
I=0 strength is at the pi-Sigma threshold of 1328 MeV with a width of 80+/-20 MeV.  Given the fact that PDG shows 
the Lambda(1405) mass at 1405+/-1 MeV, and its width at 50 +/-2 MeV, the observed "shift" of 77 MeV from our data
is really spectacular. If we are reasonably sure about this we should make a stronger statement and explicitly say that 
this corresponds to a shift from the PDG mass average by a very large value.  If this is the case, then the 'line-shape' 
issue can be seen also in a very different light. Basically, 50% of the Lambda(1405) strength would be below threshold, so the
sensitivity to the line shape comes from the higher energy part only, i.e. from the high-energy tail beyond the "peak", 
making such an analysis very difficult as the threshold behavior of the pi-Sigma production would have to be understood 
quantitatively. Perhaps one could discuss these issues somewhat more.

Volker