RapidSim is a fast Monte Carlo generator for simulation of heavy-quark hadron decays. It can be useful for generating background or toy data sets for acceptance studies.

It uses TGenPhaseSpace to generate b/c quark hadron decays.
FONLL is used to give the b/c the correct production kinematics for the LHC.
The daughter particle momenta are smeared correctly using user-defined resolutions.
Cuts can be made on daughter particle properties (pT, eta, etc).
Particle mass hypotheses can be swapped to investigate effect of mis-identification.

A more detailed description can be found here https://arxiv.org/abs/1612.07489