Position reconstruction for segmented detectors

TL;DR

This paper investigates biases in position reconstruction for segmented detectors, proposes a bias-correction method that enhances resolution, and validates it through detailed simulations and test-beam data comparisons.

Contribution

It introduces a new bias-removal method for position reconstruction in segmented detectors, improving accuracy and providing event-specific response functions.

Findings

Centre-of-gravity method is biased with narrow charge distributions.

Proposed method reduces bias and improves position resolution.

Simulation results match test-beam data, validating the approach.

Abstract

The topic of the paper is the position reconstruction from signals of segmented detectors. With the help of a simple simulation, it is shown that the position reconstruction using the centre-of-gravity method is strongly biased, if the width of the charge (or e.g. light) distribution at the electrodes (or photo detectors) is less than the read-out pitch. A method is proposed which removes this bias for events with signals in two or more read-out channels and thereby improves the position resolution. The method also provides an estimate of the position-response function for every event. Examples are given for which its width as a function of the reconstructed position varies by as much as an order of magnitude. A fast Monte Carlo program is described which simulates the signals from a silicon pixel detector traversed by charged particles under different angles, and the results obtained with the proposed reconstruction method and with the centre-of-gravity method are compared. The simulation includes the local energy-loss fluctuations, the position-dependent electric field, the diffusion of the charge carriers, the electronics noise and charge thresholds for clustering. A comparison to test-beam-data is used to validate the simulation.