Master Thesis defense by Laura Marie Dufke

Title: A Hadronic Calorimeter for ALICE

Abstract

In 2020 The ALICE Collaboration proposed to add a forward electromagnetic and hadronic calorimeter (FoCal) as an upgrade to the ALICE experiment. The first prototype for the hadronic calorimeter (FoCal-H) was tested in September 2021. These tests showed to be a promising starting point, even though issues with the readout system appeared. Throughout the rest of 2021, the FoCal-H first prototype was tested in a number of ways to pin-point which parameters needed to be optimized, and in which way this could be done. In particular, these tests focused on fully characterizing light propagation through the scintillating fibers, specifically the amount of optical crosstalk between the silicon photomultipliers (SiPMs). The results of this, as well as multiple other studies, were used to optimize the design for the FoCal-H second prototype, which was constructed in the summer of 2022. The FoCal-H second prototype was tested in the fall of 2022, at the SPS beamline at CERN, at energies from 60 to 350 GeV. The results of these tests have been examined and compared with simulations, to test the technical performance of the prototype.

This thesis revolves around characterizing the performance of the FoCal-H calorimeter components as well as analyzing the November 2022 SPS H2 testbeam data. Simulations corresponding to the testbeam detector setup was performed in order to compare and estimate the FoCal-H second prototype’s technical performance.

The performance characteristics of the FoCal-H calorimeter components, were studied with the aim of optimizing the design for a future prototype or the final design of FoCal-H. These studies focused on optical crosstalk measurements between the SiPMs, the cutting technique used on the scintillating fibers, and the ratio between the passive and active material of the FoCal-H calorimeter.

The analysis of the November 2022 SPS H2 testbeam data, as well as the analysis of the corresponding simulations, focused on a number of studies related to the source of response peaks, energy resolution, lateral shower containment, and examination of the intersections between calorimeter modules by performing a position scan. The investigation of these studies, lead to comparisons between the testbeam data and the simulations, to estimate the FoCal-H second prototype’s technical performance. The comparison studies found that the energy resolution of the testbeam data was better than the one from the simulation. In light of this result, multiple studies were performed in order to point out any potential reason. These studies included the use of physics list in the simulations, and saturation in simulations and/or in the testbeam data. A reason for this unexpected result of the energy resolution was not found, but potential other studies were suggested.