Performance of the MeV gamma-ray telescopes and polarimeters of the future. $\gamma \to e^{+}{e}^{-}$ in silicon-detector active targets

A number of techniques are being developed to solve the monstrous sensitivity gap that exists between the energy ranges of good sensitivity of the Compton and of the pair telescopes and to extend polarimetry to the MeV gamma-ray world. I characterize the properties of an active target, detailing the various contributions to the angular resolution, using a full five-dimensional event generator of the Bethe-Heitler differential cross section. With the same tool I also examine the dilution of the polarization asymmetry induced by multiple scattering in the conversion wafer.