Re: Question on Pythia Background Normalization

[Alexander Somov <somov@jlab.org>]

Hello Matt,
> I agree -- do you know if there is a routine that essentially predicts
> the probability as a function of energy for photons that interact with
> the target?  (This must be somewhere internally in HDGeant.)
>
> If this is available, it would be easy to modify some of the signal
> generators we have to draw from this distribution.

I think that we just need an energy-dependent cross section
for the signal events (specific for each signal channel).
I am not sure how to parameterize it 'correctly'. This cross
section should be simply multiplied by the photon energy spectrum
to form a production probability distribution (as function of
energy)

For every event we first distribute energy according to the
above probability function and subsequently generates the
signal decay for the specific energy. The decay products are
forwarded to Geant.

Cheers,
       Sascha