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Hi Ashot -<br>
<br>
I went through your draft this morning. Overall, it looks to be
in very good shape, and<br>
you certainly benefit from have done the proposal only a year ago. I
did have a few comments<br>
on things and hope that the following feedback is useful.<br>
<br>
*) In section 1 where you give the Pseudoscalar mixing angle with a
very precise value. I am<br>
not sure that it is possible to measure this so accurately. There
are too many experimental<br>
biases and assumptions that go into the wide range of measurements.
For example, the 2010<br>
PDG lists the mixing angle as -18+-2 from eta-prime -> two gamma
vs eta-> two gamma, <br>
but it is -24 from eta-> 2gamma vs pi0-> 2gamma. Klempt and
Zaitsev (Phys. Rep. 454, p.1 2007)<br>
give a combined number of -13.2 +- 1.2 when looking at radiative
decays to eta and eta-prime<br>
and on page 18 of there report, Figure 3 shows a nice contour plot
of this. The bottom line<br>
is that It is hard to believe that one can measure this to better
than 1-2 degrees as the wide<br>
range of definitions will mess distort your result. While an
improved gamma-gamma width<br>
will no doubt impact this mixing angle, I do not believe that it
will improve the accuracy to<br>
the level that you quote.<br>
<br>
*) I liked the discussion on the new theoretical work. That is
important to see.<br>
<br>
*) At the end of section 1 where you talk about the comp-cal. Do you
have GEANT simulations<br>
for the performance of this down stream of the FCAL? It would
certainly be very nice to be able<br>
to use it there, but I am concerned about all the the scattering
from the walls of the hole in the <br>
FCAL. You probably need to expand this a bit to show your detailed
MC results. Particularly<br>
because this is used to measure the Compton events accurately and is
crucial to your argument<br>
for separate beam time.<br>
<br>
*) You discuss the coplanarity condition as an important cut for
pulling out Comptons from the <br>
data stream, and show how the magnetic field destroys this. That is
nice to see. My question is<br>
about the impact of the material in GlueX on this angle?
Unfortunately. there is material in<br>
the FDCs along the beam line that also might impact this. Do you
have an estimate for this<br>
effect?<br>
<br>
*) While the 11 days that you were able to shave off the beam-time
request are good, you may<br>
want to caveat that those shared days need to occur close to the
start of your running. If we<br>
hit a year where only PrimEx runs, then those days would need to be
part of your requested beam<br>
time. It is probably worth pointing this out in your explanations.<br>
<br>
Cheers -- Curtis<br>
<br>
On 11/29/10 5:53 AM, Ashot Gasparian wrote:
<blockquote
cite="mid:Pine.LNX.4.64.1011290542280.15539@jlabl3.jlab.org"
type="cite">
<br>
Dear Hall D Collaborators,
<br>
<br>
We are required to submit a short update for the eta-Primakoff
<br>
proposal to this upcoming PAC37 for the beam time assignment and
<br>
scientific rating.
<br>
The proposal was approved a year ago by PAC35.
<br>
<br>
The first draft of the suggested update is in the attachment of
<br>
this email. The submission deadline is on this Wednesday, so you
<br>
will have a few days to send your critical suggestions and
questions
<br>
to us to make this document better for the submission.
<br>
<br>
Thank you for your participation and valuable support,
<br>
Ashot, Liping
<br>
<br>
<br>
<br>
.............................................................
<br>
Ashot Gasparian Phone:(336)285-2112 (NC
A&T)
<br>
Professor of Physics
<br>
Physics Department (757)-269-7914 JLab
<br>
NC A&T State University Fax:(757)-269-6273 JLab
<br>
Greensboro, NC 27411 email: <a class="moz-txt-link-abbreviated" href="mailto:gasparan@jlab.org">gasparan@jlab.org</a>
<br>
.............................................................
<br>
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<br>
<pre class="moz-signature" cols="72">--
Prof. Curtis A. Meyer Department of Physics
Phone: (412) 268-2745 Carnegie Mellon University
Fax: (412) 681-0648 Pittsburgh PA 15213-3890
<a class="moz-txt-link-abbreviated" href="mailto:cmeyer@ernest.phys.cmu.edu">cmeyer@ernest.phys.cmu.edu</a> <a class="moz-txt-link-freetext" href="http://www.curtismeyer.com/">http://www.curtismeyer.com/</a>
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