Test beam demonstration of silicon microstrip modules with transverse momentum discrimination for the future CMS tracking detector

Abstract

A: A new CMS Tracker is under development for operation at the High Luminosity LHC from 2026 onwards. It includes an outer tracker based on dedicated modules that will reconstruct short track segments, called stubs, using spatially coincident clusters in two closely spaced silicon sensor layers. These modules allow the rejection of low transverse momentum track hits and reduce the data volume before transmission to the first level trigger. The inclusion of tracking information in the trigger decision is essential to limit the first level trigger accept rate. A customized frontend readout chip, the CMS Binary Chip (CBC), containing stub finding logic has been designed for this purpose. A prototype module, equipped with the CBC chip, has been constructed and operated for the first time in a 4 GeV/c positron beam at DESY. The behaviour of the stub finding was studied for different angles of beam incidence on a module, which allows an estimate of the sensitivity to transverse momentum within the future CMS detector. A sharp transverse momentum threshold around 2 GeV/c was demonstrated, which meets the requirement to reject a large fraction of low momentum tracks present in the LHC environment on-detector. This is the first realistic demonstration of a silicon tracking module that is able to select data, based on the particle's transverse momentum, for use in a first level trigger at the LHC. The results from this test are described here. K: Front-end electronics for detector readout; Particle tracking detectors; Trigger concepts and systems (hardware and software); Trigger detectors c 2018 CERN for the benefit of the CMS collaboration.

Test beam performance of a CBC3-based mini-module for the Phase-2 CMS Outer Tracker before and after neutron irradiation

“…It should be noted that, in -20 - all runs, the fraction of clusters with width three and four, which are dominated by delta rays, do not show a strong dependence on the incident angle. All observations are in agreement with prior measurements in the literature [7]. Figure 23 compares the cluster width for the unirradiated, half irradiated, and fully irradiated mini-module.…”

“…Results from the characterization of a prototype 2S module based on the previous version of the CBC are discussed in ref. [7], while this paper presents the performance of the first module based on a version of the CBC ASIC (CBC3) that incorporates the complete functionality, including the trigger logic. This module, featuring smaller sensors and built with only two CBC chips instead of the sixteen that equip a tracker module, is called mini-module.…”

Test beam performance of a CBC3-based mini-module for the Phase-2 CMS Outer Tracker before and after neutron irradiation

“…It should be noted that, in all runs, the fraction of clusters with width three and four, which are dominated by delta rays, do not show a strong dependence on the incident angle. All observations are in agreement with prior measurements in the literature [7]. Figure 23 compares the cluster width for the unirradiated, half irradiated, and fully irradiated mini-module.…”

The Phase-2 Upgrade of the CMS Outer Tracker

“…Prototype modules of the OT have been studied at various test beam facilities at CERN, Fermilab and DESY [2,18,4]. Both full-size 2S prototype modules and 2S mini-modules read out by CBC version-2, (CBC2) chips were tested.…”