[Halld-physics] Primakov eta hadronic background

[Richard Jones]

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

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