How to use ATGEN @Victoria

After you have downloaded the user tar file and copied it to the directory of your choice, extract the contents of the archive using the command

tar xvf atgen_uvuser.tar

This will create 4 files

atgen.cmz              -- main atgen code
atgen6.hpux.ins        -- local atgen install script
my_include_w195.cmz    -- example file to include external process
wprod.datacard         -- example datacard

Issuing the command atgen6.hpux.ins will compile a version of atgen in your directory. To run it you need to pass in datacard values, a sample datacard which uses PYTHIA to create W's in PP collisions has been included. So, to run ATGEN using the sample datacard values type

atgen6.exe < wprod.datacard

If you wish to alter routines in ATGEN, you will need to know a little about the CMZ code management system. The rest of this explanation will assume that you have used CMZ before. Copy the routines you wish to change from atgen.cmz into a file called my.cmz, then change the routines within my.cmz. When atgen6.hpux.ins is compiling it will correct atgen with whatever routines you have included in my.cmz. An example "my.cmz" (my_include_w195.cmz) is included with the user files. If my_include_w195.cmz is moved to my.cmz and atgen is recompiled a new process (process 195) will have been added to PYTHIA.