The existence of a dilepton subsection in the output section of the configuration file enables the dilepton output. The output file named Dileptons (followed by the appropriate suffix) is generated when SMASH is executed. It's format is identical to the collision output (see OSCAR Collisions Format), it does however only contain information about the dilepton decays.
Further, the block headers differ from the usual collision output:

# interaction in nin out nout rho density weight shining_weight partial part_weight type proc_type

where

nin: Number of ingoing particles (initial state particles)
nout: Number of outgoing particles (finalstate particles)
density: Density at the interaction point
shining_weight: Shining weight of the interaction. Explanation follows below.
part_weight: The partial weight of the interaction. For the dileptons, this coincides with the branching ratio.
proc_type: The type of the underlying process. See process_type for possible types.

Note, that "interaction", "in", "out", "rho", "weight", "partial" and "type" are no variables, but words that are printed.
The dilepton output is available in binary, OSCAR1999, OSCAR2013 and OSCAR2013 extended format.

The treatment of Dilepton Decays is special:

Dileptons are treated via the time integration method, also called 'shining', as e.g. described in Schmidt:2008hm, chapter 2D. This means that, because dilepton decays are so rare, possible decays are written in the output at every hadron propagation without ever performing them. The are weighted with a "shining weight" to compensate for the over-production.
The shining weight can be found in the weight element of the output.
The shining method is implemented in the DecayActionsFinderDilepton, which is automatically enabled together with the dilepton output.

Note: If you want dilepton decays, you have to modify the decaymodes.txt of your choice, which you then specify as the input with the -d command line option. Without this decay modes modification the dilepton output will be empty.
Dilepton decays are commented out by default. You therefore need to uncomment them. Note, that for dilepton decays, new decay channels can not simply be added to the decaymodes.txt file. You also have to modify the decay width formulas TwoBodyDecayDilepton::width and ThreeBodyDecayDilepton::diff_width in '$SMASH_SRC_DIRECTORY/src/decaytype.cc'.

Note: As dileptons are treated perturbatively, the produced dileptons are only written to the dilepton output, but neither to the usual collision output, nor to the particle lists.