Electron Recoil


I am curious if there is a stand-alone model for electron recoil? I am looking for exotic interactions such as very light dark matter particles interacting with electrons (Not looking for multiple Scattering libraries as seen in the extended example).

I suspect that what you’re looking for is the SingleScatter (“__SS”) process. But you’re also going to need to define a new particle type for your light DM, and attach all appropriate physics processes to that new particle type.

Because the cross-section for DM interactions are so tiny, you might find it “better” in some way to write an event generator instead. There you apply the physics of your particular DM-electron interaction model, and generate the four vector of the ejected electron. Pass that four vector over to Geant4 to turn into a primary particle (e.g., run your event generator as part of a PrimaryGeneratorAction).

In general, we always assume that DM is going to interact at most one time in an apparatus (since if it interacted a lot, it wouldn’t really be “dark” matter any more).

Thanks for response, Just to clairify (“__SS”) process have inbuilt recoil physics?

Yes. The single-scatter and ionization processes will create the ejected electron as a secondary, if it has more energy than your production cut.

Thank you again! Just another small question, does only the Single Scatter process [on its own] produce any delta electrons I know the Ionization process does but I am not sure if the Single Scatter process does.

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