[Clascomment] OPT-IN:First Measurement of the Polarization Observable E in the p(gamma, pi+)n Reaction up to 2.25 GeV

[David Ireland]

Dear Steffen, et al.

You have done a great job in presenting a very nice analysis and an impressive data set. I have to agree with some of the other comments so far, however, which worry about promising new physics results, whilst not being able to show them in this paper. I think you either have to remove all forward-referencing to a new result, and plot curves from existing calculations, or include the new Bonn-Gatchina PWA fits. I appreciate that this was a particularly tricky issue with our collaborators, but there are one or two instances in the text where this compromise does not quite look right.

One other point concerns the use of the phrase "complete experiment". This is solely a mathematical concept, and any real experiment only ever measures counts of one sort or another, so:
- page 1, line 28: "at least eight observables" -> "at least eight well-chosen observables of sufficient accuracy"

Best wishes, 

Dave