Detailed Measurements of Shower Properties in a High Granularity Digital Electromagnetic Calorimeter

TL;DR

This paper presents detailed measurements of electromagnetic showers in a high granularity calorimeter prototype, enabling unprecedented comparison with simulations and highlighting areas for model improvements.

Contribution

It provides the first detailed experimental data on shower properties in a high granularity digital calorimeter, testing and challenging existing simulation models.

Findings

Discrepancies between data and Geant4 simulations highlight model limitations.

High granularity enables detailed shower structure analysis.

Data covers energies from 2 GeV to 244 GeV.

Abstract

The MAPS prototype of the proposed ALICE Forward Calorimeter (FoCal) is the highest granularity electromagnetic calorimeter, with 39 million pixels of $30 \times 30 \mu$m$^{2}$. Particle showers can be studied with unprecedented detail with this prototype. Electromagnetic showers at energies between 2 GeV and 244 GeV have been studied and compared to Geant4 simulations. Simulation models can be tested in more detail than ever before and the differences observed between FoCal data and Geant4 simulations illustrates that improvements in electromagnetic models are still possible.