CMS Phase-2

CMS Phase-2
Name	CMS Phase-2 Upgrade
Location	CERN, Meyrin
Start	2017
Expected completion	2027
Budget	≈€800 million
Participants	CMS Collaboration, CERN, European Union, US Department of Energy, National Science Foundation

CMS Phase-2

The CMS Phase-2 upgrade is the high-luminosity-era modernization of the Compact Muon Solenoid experiment at the CERN Large Hadron Collider facility in Meyrin. It prepares the Compact Muon Solenoid detector for the High-Luminosity Large Hadron Collider run to sustain physics programs pursued by collaborations such as ATLAS, LHCb, and ALICE while coordinating with funding agencies like the European Commission, the United States Department of Energy, and the National Science Foundation. The upgrade spans detector hardware, trigger and data-acquisition systems, and offline computing to handle luminosity and pileup conditions anticipated from the High-Luminosity LHC.

Introduction

The Phase-2 effort modernizes the Compact Muon Solenoid apparatus that recorded the discovery-era datasets alongside experiments including ATLAS and LHCb during Run 1 and Run 2, building on technologies developed for projects such as the CMS Phase-1 upgrade and initiatives at facilities like the European XFEL and the Fermilab Tevatron. It aligns with strategic roadmaps produced by bodies including the European Strategy for Particle Physics and the Particle Physics Project Prioritization Panel to maximize physics reach in searches that connect to results from experiments such as Belle II, IceCube, and NOvA.

Motivation and Objectives

The primary goal is to enable precision measurements and rare-process searches at integrated luminosities targeted by the High-Luminosity LHC program to probe signatures connected to theories like supersymmetry tested by ATLAS and CMS and to complement flavor results from LHCb and Belle II. Objectives include sustaining tracking and vertexing performance under extreme pileup conditions envisioned by High-Luminosity LHC planners, improving electromagnetic calorimetry resolution that benefited analyses such as the Higgs boson mass measurement, and extending muon-system capabilities used in studies of anomalies reported by collaborations like Fermilab Muon g-2 and experiments at J-PARC. The upgrade seeks to preserve discovery potential for phenomena considered in proposals like Dark Matter searches and heavy-ion programs linked to ALICE.

Detector Upgrades and Design

Phase-2 replaces or augments major subsystems: a new silicon inner tracker inspired by technologies from the ATLAS ITk and leveraging sensor R&D at institutions such as CERN, Fermilab, Brookhaven National Laboratory, and DESY; high-granularity calorimetry building on concepts from the CALICE collaboration and developments at SLAC National Accelerator Laboratory; extended muon coverage with new electronics and detectors similar to upgrades at ATLAS and LHCb; and a two-level trigger and data-acquisition architecture harmonized with readout models developed by ALICE and the LHC experiments. The design incorporates radiation-hard silicon pixel and strip sensors, precision timing layers influenced by projects like the MIP Timing Detector and detector efforts at KEK, and upgraded front-end electronics compatible with the GigaBit Transceiver ecosystems used across LHC experiments.

Technical Challenges and R&D

Key challenges include radiation tolerance under fluences estimated by High-Luminosity LHC studies, timing resolution at the tens-of-picoseconds scale pursued in programs at CERN and SLAC, and high-bandwidth data transport compatible with protocols developed by collaborations such as ATLAS and LHCb. R&D efforts span sensor development at facilities like Fondazione Bruno Kessler and IMB-CNM, ASIC design initiatives related to projects at IRFU and LPNHE, cooling and mechanics concepts drawing on work from CERN and DESY, and system integration lessons from experiments such as CMS Phase-1 upgrade and the ATLAS IBL. Simulation and validation use computing infrastructures coordinated with the Worldwide LHC Computing Grid and analysis frameworks shared by CMS and ATLAS.

Construction, Commissioning, and Schedule

Construction phases follow procurement and fabrication across partner laboratories including CERN, Fermilab, Brookhaven National Laboratory, DESY, KEK, and university groups tied to institutions like Imperial College London and MIT. Commissioning integrates subsystems during long shutdowns planned by CERN and test beam programs at facilities such as the CERN PS and Fermilab Test Beam Facility. The schedule coordinates with LHC operational periods, with major installations targeted during Long Shutdown 3 and final commissioning ahead of the High-Luminosity LHC run, mirroring timelines established by the European Strategy for Particle Physics and project reviews by agencies like the DOE.

Physics Program and Expected Performance

With upgraded tracking, timing, calorimetry, and muon systems, the experiment aims to deliver precision Higgs boson coupling measurements complementing results from ATLAS and future lepton colliders, improved sensitivity to rare decays akin to studies at LHCb and Belle II, and enhanced discovery reach for beyond-Standard-Model scenarios explored alongside searches at Fermilab and SLAC. Expected performance targets include vertex resolution improvements informed by Pixel detector R&D, jet substructure and pileup mitigation leveraging experience from ATLAS analyses, and per-event timing resolution that supports particle-flow reconstruction concepts developed in collaboration with experiments such as ALICE.

Collaboration, Funding, and Project Management

The upgrade is coordinated by the CMS Collaboration governance structures with contributions from national laboratories and universities across Europe, North America, and Asia, managed through memoranda of understanding with agencies including the European Commission, the United States Department of Energy, the National Science Foundation, and national funding bodies from countries involved in detector deliverables. Project management uses review processes modeled on those at CERN and program offices at Fermilab and Brookhaven National Laboratory, with oversight from advisory panels similar to the Particle Physics Project Prioritization Panel and committees established under the European Strategy for Particle Physics.

Category:Particle detectors