Reconstruction and Particle Identification for a DIRC System

TL;DR

This paper presents a novel approach for particle identification in DIRC systems using stereographic projection and circle fitting algorithms, effectively handling background noise to improve PID accuracy.

Contribution

It introduces a stereographic projection method and a reliable circle fitting algorithm for improved particle identification in DIRC systems, even with high background levels.

Findings

Effective background removal without degrading reconstruction quality

Reliable circle arc fitting for small angular openings

Enhanced PID performance with the proposed algorithms

Abstract

We study the reconstruction and particle identification (PID) problem for Ring Imaging devices providing a good knowledge of the direction of the Cerenkov photons, as the DIRC system, on which we specialize. We advocate first the use of the stereographic projection as a tool allowing a suitable representation of the photon data, as it allows to represent the Cerenkov cone always as a circle. We set up an algorithm able to perform reliably a fit of circle arcs of small angular opening, by minimising a true Chi2 expression. The system we develop for PID relies on this algorithm and on a procedure able to remove background photons with a high efficiency. We thus show that, even when the background is large, it is possible to perform an efficient PID by means of a fit algorithm which finally provides all the circle parameters; these are connected with the charged track direction and its Cerenkov angle. It is shown that background effects can be dealt without spoiling significantly the reconstruction probability distributions.