[Clascomment] First observation of the line shape of the Lambda(1405) in electroproduction

[Reinhard Schumacher]

Hello Kijun,

	Here are the replies to your questions.  The revised version of the 
paper has been posted to the CLAS reviews web site.

Sincerely,
Reinhard and Haiyun

 > Dear Haiyun et al.,
 >
 > This is an interesting result.
 > Many people who were in the last NStar2013 workshop talked about the 
line shape and pole position in Lambda(1405).
 > In particular, HADES experiment also claimed two pole positions but 
different values from the CLAS photoproduction.
 > I hope this new result will provide some hints for better understanding.
 > I have couple of comments(minor) and questions (You might have 
answered in the analysis review but it is just for my understanding).
 >
 >
 > 1/ Overall (many places), the kinematic variable units are not 
correct...such as t, Q2. ..

Yes, we have fixed all these places.

 > 2/ Just wondering, isn't it useful if you have a full paper, or plan ?
 >     Most of figures is showing "missing mass of e'K+" in the short paper.

This is as full a paper as we plan to write.  The result is interesting, 
as you say, but not terribly strong, and there is a limit to how much we 
can do with it.  Our goal is to make the case for making higher 
statistics measurements, and we think this paper does that.

We're not sure if you are making a second point with your comment about 
the figures.

 > 3/ line 78: It seems that this is a bit strong statement.
 >     How you can claim this peak is Lambda(1405) "CLEARLY"?
 >     Your acceptance corrected plot shows a quite different, 
especially Fig3(a).

We have changed this place in the text (among many others).  The claim 
has been reworded to be softer and to be more clear.  The acceptance 
correction is largest at the threshold.  There is no way around that. We 
spent a lot of time doing tests to convince ourselves that the 
correction is reliable.

 > 4/ Fig2 shows the pi0 missing mass on y-axis. what's the reason of 
negative mass event ?
 > Is it better to show in MM2 ?

We changed this figure since it was potentially confusing, as you say. 
The events in the corner near zero missing mass were from 
electroproduction of the ground state Lambda.  We now have cut away that 
portion of the plot.

 > 5/ It might be a negligible but ... How did you take into account the 
radiative effect ?
 >     In line124-125, you said your MC was well matched with data.
 >     The only event selecting works for matching without tune other MC 
parameters ?
 >     what do you mean "\phi to tailor the Monte-Carlo distribution 
used in ..." ?

It already states in the paper that we did not make radiative 
corrections.  With the statistics we have it can hardly matter. The fits 
we make do include Breit-Wigner functions with a freely-floating width. 
  In principle, if the distribution gets stretched out a bit due to 
radiative effects, at our level of precision the fit should just 
accommodate it by increasing the width.   As you can see, there is no 
way we can be sensitive to finer details of the line shape.  See below 
re the phi distribution.

 > 6/ In your statements, you did not take into account \phi*, (\theta*) 
bins.
 >     How did you treat missing \phi*, \theta* bin in your yield ?
 >     Your events are filled into all your angles, Q2 bins ?
 >

The polar angle theta* WAS one of the binnings used in the Monte Carlo. 
  We did not bin in phi*.  This is like assuming the LT and TT 
interference functions are negligible.   It is indeed an assumption. 
When we compared the generated and reconstructed phi distributions 
(which we could do even though we did not bin the Monte Carlo in phi), 
there was quite good agreement immediately with the phase space 
generator.  But then we selected events to match this distribution 
exactly as a way of estimating the systematic associated with this 
assumption.  For the full story, please take a look at the posted 
analysis note.

 >
 > Thank you in advance for your kindly response.
 > Sincerely yours,
 > Kijun


___________________________________________________________________
Reinhard Schumacher         Department of Physics, 5000 Forbes Ave.
Carnegie Mellon University, Pittsburgh, PA 15213, U.S.A.
phone: 412-268-5177         web: www-meg.phys.cmu.edu/~schumach
___________________________________________________________________