Performance of the Electromagnetic Pixel Calorimeter Prototype EPICAL-2

TL;DR

This paper evaluates an ultra-high granularity digital electromagnetic calorimeter prototype with 25 million pixels, demonstrating competitive energy resolution and promising potential for high-energy physics applications.

Contribution

It presents the first performance evaluation of a novel pixel calorimeter prototype using CMOS MAPS sensors with detailed measurements and simulation validation.

Findings

Energy resolution comparable to state-of-the-art calorimeters

Good agreement between data and GEANT/Allpix$^2$ simulations

Suitable for ALICE FoCal upgrade and future high-energy physics use

Abstract

The first evaluation of an ultra-high granularity digital electromagnetic calorimeter prototype using 1.0-5.8 GeV/c electrons is presented. The $25\times10^6$ pixel detector consists of 24 layers of ALPIDE CMOS MAPS sensors, with a pitch of around 30~$\mu$m, and has a depth of almost 20 radiation lengths of tungsten absorber. Ultra-thin cables allow for a very compact design. The properties that are critical for physics studies are measured: electromagnetic shower response, energy resolution and linearity. The stochastic energy resolution is comparable with the state-of-the art resolution for a Si-W calorimeter, with data described well by a simulation model using GEANT and Allpix$^2$. The performance achieved makes this technology a good candidate for use in the ALICE FoCal upgrade, and in general demonstrates the strong potential for future applications in high-energy physics.