GELHAD in BBSIM

This package(|gelhad|) is used to generate hadronic 
interactions of electro-magnetic particles. It contains 
modified version of the relevant |geant| routines (e.g., 
|gtgama|) as well as the specific code to generate these 
interactions.

To turn |gelhad| on you need to pick up the |gelhad| 
package and to define |_GELH_| in |gnbase/src/Flags.h|.

Thu Nov  2 11:02:07 PST 1995

Parameters for controlling |gelhad| are local variables
in the modified version of |gtgama|. They can be set using
|ffread| cards in your input file.

Parameter   Default     Meaning
jphadr          1       0=>off; 1=>on
ecutphadr       0.5 GeV     min energy for hadronic 
                interaction to be on.
scale       1.0     x-section scale factor
mode_gphad  4       controls model used
                 1=>g->N absorption model
                 2=>g->pi gamma becomes pi model
                 3=>undefined
                 4=>hybrid model
                  g->N below "pi" threshold
                  g->pi above "pi" threshold
ethresh_gphad   0.150       effective pi threshold for 
                mode=4.


Key word for input of these parameters is GELH. Order
of parameters on GELH card is order in table above.

Example:
C |gelhad| parameters
C     jphadr ecut  scale mode  thresh
GELH  1      0.2   1.0   4     0.160

Fri Nov  3 10:11:55 PST 1995

To enable |gelhad| you must (in addition to having at
GELH card in your input file), have a |#define _GELH_ 1| line
in your |Flags.h| file.

I gather from Torre that this method of control (|ffread|) is or
is becoming obsolete, so look for change over to |run.db|
control some time soon(?).