CMS Phase-2 Upgrade

CMS Phase-2 Upgrade
Name	CMS Phase-2 Upgrade
Location	CERN
Started	2017
Planned completion	2027
Participants	CERN, Fermilab, DESY, University of California, Berkeley, Imperial College London, INFN

CMS Phase-2 Upgrade The CMS Phase-2 Upgrade is a comprehensive modernization of the Compact Muon Solenoid experiment to operate at the High-Luminosity Large Hadron Collider for the Run 4 and beyond. Motivated by the goals of extending sensitivity to rare processes and enhancing precision for searches connected to the Higgs boson, supersymmetry, and dark matter scenarios, the project replaces and augments subsystems across tracking, calorimetry, and muon detection. Collaboration among institutions such as CERN, Fermilab, DESY, INFN, SLAC National Accelerator Laboratory, and major universities drives detector development, trigger redesign, and data acquisition overhaul.

Background and Motivation

Upgrading to Phase-2 responds to the increased instantaneous luminosity delivered by the High-Luminosity LHC upgrade of the Large Hadron Collider accelerator complex at CERN. The higher pileup conditions anticipated for Run 4 and Run 5 necessitate improved radiation hardness and granularity to preserve performance for measurements like the Higgs boson self-coupling and searches for vector-like quarks, supersymmetric particles, and exotic resonances explored at facilities such as ATLAS and LHCb. The physics case was developed in coordination with working groups tied to the European Strategy for Particle Physics and advisory bodies including the Particle Physics Project Prioritization Panel and the P5.

Detector Upgrades

The upgrade replaces the inner tracking system with a new silicon tracker composed of pixel detector layers and silicon strip detector modules designed for radiation tolerance comparable to those used at SLAC National Accelerator Laboratory and DESY. The electromagnetic calorimeter retention and upgrades include improved front-end electronics inspired by developments at KEK and BNL, while the hadronic calorimeter receives new photodetectors and high-speed readout similar to techniques from Fermilab and INFN. The muon system integrates upgraded GEM and Micromegas chambers, technologies validated in test beams at CERN SPS and facilities like J-PARC. Precision timing layers employing low-gain avalanche detectors (LGADs) provide ~30 picosecond resolution, advancing methods pioneered at CERN, University of Geneva, and University of California, Santa Cruz.

Trigger and Data Acquisition

Phase-2 introduces a two-tiered trigger architecture combining a hardware-based Level-1 trigger with a high-level trigger farm leveraging commercial processors and custom FPGA boards developed in collaboration with vendors engaged by CERN and Fermilab. The Level-1 system integrates track information from the new tracker and calorimeter primitives to refine selection akin to trigger strategies used at ATLAS and Belle II. The data acquisition system scales to handle multi-terabit-per-second links using optical transceivers and protocols tested at SLAC, DESY, and the European XFEL project. Software frameworks for online reconstruction draw on efforts from ROOT and common tools shared with experiments like IceCube and NOvA.

Installation and Commissioning

Installation follows coordinated shutdown periods at the Large Hadron Collider with integration performed in experimental halls at Point 5 under procedures similar to those used for the original CMS construction and major upgrades involving teams from CERN, Fermilab, and INFN. Commissioning activities include cosmic-ray runs, test beams at the CERN SPS, and calibration campaigns informed by experience from CMS Run 2 and commissioning practices deployed at LHCb and ALICE. Safety reviews and quality assurance follow standards established by CERN committees and national funding agencies such as DOE and INFN.

Performance Projections and Physics Impact

Simulation studies using tools like GEANT4 and reconstruction algorithms benchmarked against Run 2 data project substantial gains in object identification, vertex resolution, and pileup mitigation. Improvements enable precise measurements of the Higgs boson couplings, differential cross sections relevant to Quantum Chromodynamics, and enhanced sensitivity to signatures predicted by supersymmetry and extra dimension models explored at CERN. Projected limits on rare processes and exotic resonances match exploratory programs coordinated with global efforts at KEK, SLAC, and Fermilab for next-generation discovery potential.

Project Management and Timeline

The upgrade follows milestone-driven management with funding and oversight from agencies including the European Commission-backed programs, DOE Office of Science, and national research councils. Key milestones align with the High-Luminosity LHC schedule, with major installations completed during Long Shutdown 3 and commissioning aimed before Run 4. Collaboration governance mirrors structures used by large experiments such as ATLAS and IceCube, balancing institutional responsibilities across detector construction, integration, and computing infrastructure.

Category:Particle physics projects