[Halld-offline] pairspectrometer talk at Hall D meeting

[Richard Jones]

Pawel,

Yes, it only applies when an external event generator is used.  To see 
this, look in the source file hddmInput.c and follow the use of the 
symbols TARGET_LENGTH and BEAM_DIAMETER.  If you see the event vertex 
smeared in z by TARGET_LENGTH then you automatically are also getting it 
smeared in x,y by BEAM_DIAMETER.

If the internal coh. brems. generator is used then the distribution is 
not uniform, but follows the bremsstrahlung differential cross section 
folded with the CEBAF beam phase space profile.

-Richard Jones


pawel at jlab.org wrote:
> Richard,
>
> During my talk at last Physics Group meeting
> you said that x and y beam positions are uniformly smeared.
> That doesn't apply when an external event generator input
> is used, does it?
>
> Many thanks for any help,
> Pawel
>
>
>   

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