[Halld-physics] Primakov eta hadronic background

[Ashot Gasparian]

   Hi Richard,

   I agree that the combinatorial background is also important
  and it is coming from two photons from different events.
  As I already wrote in my previous email, the major source of
  that (at least providing the one gamma) is coming from the
  electromagnetic (beam) background, we have done some simulation
  in this with Pawel and will try to put together some plots
  for this type of the background.

  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
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On Wed, 2 Dec 2009, Richard Jones wrote:

> Alex,
>
> Thank you for the quick study you did.  However I am puzzled by the suggested 
> conclusion.  By combinatorial background, one means etas that are 
> reconstructed out of photons that did not come from an eta.  Maybe this is 
> small, but it is going to take considerable work to show it.
>
> Alexander Somov wrote:
>> ( The inclusive eta background should dominate combinatorial bg)
>> 
> ... in light of ...
>> (I selected events containing at least one eta in the final
>> state  with an angle < 1.6 deg, and processed these events
>> through Geant).
>> 
> To study the combinatoric background you need to look at the inclusive 
> sample.  Why should you require an eta if you are looking for 2gamma 
> combinatorial background under the eta?  I believe this restriction can lead 
> to a severe underestimate of the combinatorial background under the eta.
>
> -Richard Jones
>
>