Calorimeter-less gamma-ray telescopes: Optimal measurement of charged particle momentum from multiple scattering by Bayesian analysis of Kalman filtering innovations

TL;DR

This paper introduces a Bayesian Kalman filter-based method to measure charged particle momentum in calorimeter-less gamma-ray telescopes, enabling effective energy estimation within the active target material itself.

Contribution

It presents a novel approach for momentum measurement using multiple scattering and Bayesian analysis, suitable for low-density gamma-ray telescope designs.

Findings

Effective momentum measurement up to a few GeV/c

Applicable to silicon wafer stack telescopes

Improves energy estimation without calorimeters

Abstract

Novel gamma-ray telescope schemes (silicon wafer stacks, emulsions, gas detectors) are being developed so as to bridge the sensitivity gap between Compton and pair-creation telescopes. The lower average density with respect to the tungsten/silicon active target of the Fermi-LAT makes large 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 of the space mission. 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. For a silicon-wafer-stack telescope, the method yields meaningful results up to a couple of GeV/c.