[Halld-physics] draft text of the eta-Primakoff proposal update

[Ashot Gasparian]

   Dear Curtis,

   Thanks for your valuable inputs in this update. We will work
  on each of them and try to incorporate them in the final document.

   For the sensitivity of error on mixing angle: that formula in the
   update and in the proposal is from Jose. I will discuss with him
   that part with him again to see if there are any errors in that
   estimation. Though, I remember that the mixing angle determination is
   most sensitive to the eta to two gamma decay width, not to others like
   the eta prime.

   We will take a careful look to your suggestions and use them for the
   final document.

   Thanks a lot,
   Ashot


.............................................................
Ashot Gasparian                    Phone:(336)285-2112 (NC A&T)
Professor of Physics
Physics Department                       (757)-269-7914 JLab
NC A&T State University              Fax:(757)-269-6273 JLab
Greensboro, NC 27411               email: gasparan at jlab.org
.............................................................


On Mon, 29 Nov 2010, Curtis A. Meyer wrote:

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