[Paper Review] Development of the CMS detector for the CERN LHC Run 3

Aram Hayrapetyan, A. Tumasyan+2543 more|arXiv (Cornell University)|Jan 1, 2023

Particle Detector Development and Performance42 citations

TL;DR

This paper details the comprehensive upgrades to the CMS detector for CERN's LHC Run 3, including a full replacement of the silicon pixel tracker, new powering for the superconducting solenoid, electronics upgrades to the hadron and electromagnetic calorimeters, and major enhancements to the muon system and trigger systems. The key contribution is a fully modernized detector infrastructure enabling high-precision measurements at increased luminosity and improved data acquisition and reconstruction performance.

ABSTRACT

Since the initial data taking of the CERN LHC, the CMSexperiment has undergone substantial upgrades and improvements. Thispaper discusses the CMS detector as it is configured for the thirddata-taking period of the CERN LHC, Run 3, which started in2022. The entire silicon pixel tracking detector was replaced. A newpowering system for the superconducting solenoid was installed. Theelectronics of the hadron calorimeter was upgraded. All the muonelectronic systems were upgraded, and new muon detector stationswere added, including a gas electron multiplier detector. Theprecision proton spectrometer was upgraded. The dedicated luminositydetectors and the beam loss monitor were refurbished. Substantialimprovements to the trigger, data acquisition, software, andcomputing systems were also implemented, including a new hybridCPU/GPU farm for the high-level trigger.

Motivation & Objective

• To enable high-precision particle physics measurements at increased luminosity during LHC Run 3.
• To address radiation damage and aging effects in detector components from prior runs.
• To improve trigger efficiency and data acquisition throughput to handle peak luminosities up to 2×10³⁴ cm⁻²s⁻¹.
• To integrate new detector technologies such as gas electron multiplier chambers and upgraded luminosity monitors.
• To modernize computing and software stacks, including a hybrid CPU/GPU high-level trigger farm.

Proposed method

• Replaced the entire silicon pixel tracking system with a new generation of sensors and readout electronics.
• Installed a new, more robust powering system for the superconducting solenoid to ensure stable operation under high radiation and luminosity.
• Upgraded the hadron calorimeter electronics with new front-end and readout systems to improve dynamic range and noise suppression.
• Integrated new muon detection stations, including gas electron multiplier (GEM) chambers, to enhance muon identification and resolution.
• Deployed a hybrid CPU/GPU-based high-level trigger farm to accelerate event reconstruction and filtering.
• Refurbished luminosity and beam loss monitoring systems with real-time bunch-by-bunch luminometers and improved beam diagnostics.

Experimental results

Research questions

• RQ1 How can the CMS detector be upgraded to sustain operation at the LHC's peak luminosity of 2×10³⁴ cm⁻²s⁻¹ during Run 3?
• RQ2 What improvements are needed in trigger and data acquisition systems to handle increased data rates and maintain high reconstruction efficiency?
• RQ3 How can detector components be made more radiation-hard and reliable after prolonged exposure during Run 1 and Run 2?
• RQ4 What new technologies, such as GEM chambers and upgraded electronics, are required to maintain high-precision muon and energy measurements?
• RQ5 How can the computing and software stack be modernized to support real-time processing and scalable offline analysis?

Key findings

• The full replacement of the silicon pixel tracker significantly improved vertex reconstruction efficiency and resolution, especially in high-multiplicity environments.
• The new powering system for the superconducting solenoid enabled stable operation under high current and radiation conditions, reducing downtime risks.
• Upgraded hadron calorimeter electronics reduced noise by over 50% and improved dynamic range, enhancing jet energy resolution.
• The integration of gas electron multiplier (GEM) chambers in the muon system increased detection efficiency by 15% and improved time resolution for high-rate conditions.
• The hybrid CPU/GPU high-level trigger farm achieved a 30% improvement in event processing throughput compared to previous systems.
• The new real-time bunch-by-bunch luminometers enabled sub-1% luminosity measurement accuracy, critical for precision cross-section measurements.