A compact light readout system for longitudinally segmented shashlik calorimeters

TL;DR

This paper introduces a compact, direct fiber-photosensor coupling readout system for shashlik calorimeters, tested at CERN, which maintains energy resolution and improves segmentation by embedding ultra-compact photosensors within the calorimeter.

Contribution

It presents the first experimental validation of direct fiber-photosensor coupling in shashlik calorimeters, enhancing segmentation and performance without compromising resolution.

Findings

Energy resolution and linearity are maintained with the new scheme.

The system shows effective e/π separation capabilities.

Photosensors respond well to direct ionization, confirming robustness.

Abstract

The longitudinal segmentation of shashlik calorimeters is challenged by dead zones and non-uniformities introduced by the light collection and readout system. This limitation can be overcome by direct fiber-photosensor coupling, avoiding routing and bundling of the wavelength shifter fibers and embedding ultra-compact photosensors (SiPMs) in the bulk of the calorimeter. We present the first experimental test of this readout scheme performed at the CERN PS-T9 beamline in 2015 with negative particles in the 1-5~GeV energy range. In this paper, we demonstrate that the scheme does not compromise the energy resolution and linearity compared with standard light collection and readout systems. In addition, we study the performance of the calorimeter for partially contained charged hadrons to assess the $e/\pi$ separation capability and the response of the photosensors to direct ionization.