Monte Carlo matching in the Belle II software

The Belle II experiment is an upgrade to the Belle experiment, and is located at the SuperKEKB facility in KEK, Tsukuba, Japan. The Belle II software is completely new and is used for everything from triggering data, generation of Monte Carlo simulation, tracking, clustering, and for high-level analysis. One important feature is the matching between the combinations of reconstructed objects which form particle candidates and the underlying simulated particles from the event generators. This is used to study detector effects, analysis backgrounds, and efficiencies. This document describes the algorithm that is used by Belle II