Classification of light charged particles in a nuclear physics experiment

The problem considered in this work is pulse shape discrimination in a nuclear physics experiment. Each nucleus produced in the collision of a heavy ion beam over a target enters a detector and creates a light pulse signal measured by a digital acquisition system. The pulse shape contains complete information on the hitting particle, but it includes also the dynamics of the charge preamplifier used in the measurement. In this work, a complete procedure for the particle identification is proposed. First, a model of the charge preamplifier is estimated using experiments specifically devoted to this aim. Then, the measured pulses are filtered through the inverse model of the preamplifier and, then, a subspace method is used to estimate a linear model of the light generation process in the detector. Finally, the expectation-maximization algorithm is used for particle classification on the basis of the estimated parameters of the light pulses. This work focuses on light charged particles (LCP), which are the most difficult to detect and to classify. All the experiments are made with the large detector array CHIMERA (charge heavy ions mass and energy resolving array).