[Halld-offline] ISTORY variable in HDGeant

[Richard Jones]

Hello Yi,

The ISTORY variable keeps track of whether the particle has descended (as a
secondary of a secondary, ....) from a particle that came back out of one
of the calorimeters.  Any time a particle enters the BCal or FCal, it gets
marked with its ISTORY > 0.  This variable is inherited from your parents,
so it allows us to separate shower particles and their descendents from
particles that do not belong to the splash-back part of the secondaries
tree.

-Richard Jones


On Thu, Oct 10, 2013 at 12:48 PM, Yi Qiang <yqiang at jlab.org> wrote:

>  Hi Richard,
>
> I am studying the EM background in the DIRC detector. One of the
> information I am collecting is the background hit in the DIRC window, so
> called RichTruthHit. I'm using the embedded photon generator in HDGeant
> together with a BGGATE to generate the background. What I found that
> requiring ISTORY equal to zero or not makes a huge difference. I lose a lot
> of hits if I use this cut. So I am wondering what's the meaning of this
> variable since the truth hits in other detectors all require it.
>
> Thanks,
> Yi
>
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