Performance and Molière radius measurements using a compact prototype of LumiCal in an electron test beam

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 Molière 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 Molière radius on the electron energy in the range 1-5 GeV was also studied. Good agreement was obtained between data and MC simulation.

Luminometers for Future Linear Collider Experiments

“…The effective Molière radius is found to be 8.1±0.1 mm for 5 GeV energy, a value in agreement with 8.4±0.1 mm [12] obtained through MC simulations. A slight dependence of the Molière radius on the electron energy is understood to be caused by the limited number of detector layers installed.…”

The International Linear Collider (Report to Snowmass 2021)

“…The forward regions of the ILC detectors will be equipped with dedicated luminosity calorimeters, described in Sections 6.2.4 and 6.3.6. Recent test beam results obtained with prototype detectors [180] underpin the assumptions on the hardware made in previous detailed simulation studies, which show that the luminosity can be measured to 2.6 × 10 −3 and 1.6 × 10 −3 at center-of-mass energies of 500 and 1000 GeV, respectively [181]. The energy calibration of the calorimeter contributes to the total uncertainty at the level of 1 × 10 −3 .…”

R&D for compact calorimeters for e+e− colliders and their application to the LUXE experiment

“…Integration over r, from 0 to R M , defines 90% of the deposited energy. The effective Moliere radius R M is found to be: 8.1 ± 0.1(stat) ± 0.3(syst) mm [10] for 5 GeV electrons. The effective Molière radius depends a bit on the electron energy due to a limited longitudinal coverage with the existing number of detector planes.…”