Optimal measurement of charged particle momentum from multiple scattering: Bayesian analysis of filtering innovations

Novel gamma-ray telescope schemes are under development so as to bridge the 0.1-100 MeV sensitivity gap of gamma-ray astronomy (Compton, pair creation), (silicon wafer stacks, emulsions, gas detectors). The lower average density with respect, e.g. to the tungsten/silicon active target of the Fermi-LAT makes square-meter effective area telescopes voluminous objects, for which the photon energy measurement by conventional means (calorimeter, magnetic spectrometer, transition radiation detector) is a challenge for the mass budget. We present an optimal measurement of track momentum by the multiple measurement of the angular deflections induced by multiple scattering in the active target itself, using a Bayesian analysis of the filtering innovations of a series of Kalman filters applied to the track.