Re: Question on Pythia Background Normalization

[Eugene Chudakov <gen@jlab.org>]

One has to assume some energy dependence of the hybrid production
cross section. Let us assume it is flat in the range of our search.

Let us search for the hybrids in the beam energy range of 8.4-9 GeV.
We may simulate BGGEN events in this, or wider energy range.
BGGEN prints out the "rate" in the range used, in kHz, corresponding to
certain beam conditiones. We can select only the events in the 8.4-9 GeV
range and find the corresponding rate.

Since the bggen cross section is flat within the range and is about 120ub,
the expected number of 1 mb hybrid events at the given conditions will
be 1/120 of the bggen number of events.

The spectrometer acceptance may modify the ratio.

If the hybrid cross section depends on the energy one has to convolute
it with the beam spectrum in the same way as is done for bggen.

Eugene

On Thu, 31 Jul 2008, Matthew Shepherd wrote:

>
> On Jul 31, 2008, at 12:32 PM, Alexander Somov wrote:
>
> > (Ideally, it would be nice to tune the signal event generator
> > to allow for event generation in some specific energy range rather
> > than for a fixed beam energy)
>
>
> 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.
>
> -Matt
>
>
>