[Halld-offline] how to run hdgeant without the dirc

Richard Jones richard.t.jones at uconn.edu
Tue Jan 29 12:49:18 EST 2019

Dear colleagues,

There are two separate problems to be addressed regarding the use of
hdgeant in the post-DIRC era.

   1. how to run pre-DIRC geometry, when the DIRC is present in the master
   branch of hdds
   2. how to run with the DIRC present, but not suffer the overhead of
   following CKOV photons

For #1, please see my howto at

For #2, I recommend that you go into your control.in and change CKOV 1 to
CKOV 0. I could force this in the code, but there are situations where it
would be useful to have them enabled, and that is what the CKOV flag is
there for. As soon as you turn CKOV 0 in your control.in, the overhead
associated with the DIRC will disappear from your simulation and you will
have the material present but not the slow-down.

Setting CKOV 0 rather than hard-wiring it in the code makes sure that you
are making simulations that are directly comparable between hdgeant and
hdgeant4 when running on the same control.in. This is a design feature.

-Richard Jones
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