Our group has provided the official SHiP sensitivity estimates for the νMSM, the SHiP flagship theory, and for dark photons, the gauge bosons of a minimalistic theory based on the breaking of a U(1) symmetry in the HS.
The SHiP physics sensitivities are evaluated on the basis of the official simulation and reconstruction package, called FairShip, to the development of which our group contributed substantially, and of a fast Monte Carlo simulation developed i our group in order to determine both the rate of HNLs produced at the target and the acceptance of the HNL decay products. From these estimates, the expected number of events in 5 years of SHiP operation is calculated.
The official software and the fast simulation were compared and validated against each other. The official software, that contains a full Geant4 description of the material and detector geometry, was used to devise offline selections able to suppress the background while maintaining a large signal acceptance. To assess the impact of the reconstruction and selection on the signal, a
correction to the fast simulation is applied as a function of the mass
of the HNL, based on the outcome of the full simulation, separately for two body and three body decays.