# Performance and Moli`ere radius measurements using a compact prototype of LumiCal in an electron test beam

## TL;DR

This paper presents a new compact detector design for electromagnetic calorimeters, tested with electron beams, measuring the Molière radius accurately and validating the results with Monte Carlo simulations.

## Contribution

It introduces a novel detector plane technology and demonstrates its performance in a prototype LumiCal, including precise Molière radius measurements and energy dependence analysis.

## Key findings

- Effective Molière radius at 5 GeV is 8.1 mm with uncertainties.
- Monte Carlo simulation reproduces the measured Molière radius well.
- The Molière radius dependence on energy from 1 to 5 GeV was characterized.

## Abstract

A new design of a detector plane of sub-millimetre thickness for an electromagnetic sampling calorimeter is presented. It is intended to be used in the luminometers LumiCal and BeamCal in future linear $e^+e^-$ collider experiments. The detector planes were produced utilising novel connectivity scheme technologies. They were installed in a compact prototype of the calorimeter and tested at DESY with an electron beam of energy 1-5 GeV. The performance of a prototype of a compact LumiCal comprising eight detector planes was studied. The effective Moli`ere radius at 5 GeV was determined to be (8.1 +/- 0.1 (stat) +/- 0.3 (syst)) mm, a value well reproduced by the Monte Carlo (MC) simulation (8.4 +/- 0.1) mm. The dependence of the effective Moli`ere radius on the electron energy in the range 1-5 GeV was also studied. Good agreement was obtained between data and MC simulation.