v2.1.0 : Allow for A' Decay and Kinematics Scaling

Excellent work done by @RobMina in order to enable scaling of the dark photon's kinematics (in the same manner as the recoiling lepton's) and to allow for the G4APrime particle to decay to electron-positron pair at either a fixed lifetime or uniformly-random sampled distance.

What's Changed

• visible decay and A' kinematics scaling by @RobMina in #33

New Contributors

• @RobMina made their first contribution in #33

Full Changelog: v2.0.3...v2.1.0