LHCb Upgrade

LHCb Upgrade
Name	LHCb Upgrade
Location	CERN
Type	Particle physics experiment
Parent	Large Hadron Collider

LHCb Upgrade

The LHCb Upgrade is a major enhancement program at CERN for the Large Hadron Collider experiment designed to study CP violation, heavy-flavour physics and rare decays with improved precision and higher rate capability. The project follows the original LHCb detector's successful measurements of phenomena such as CP violation in the B meson system, contributing to global efforts by collaborations including ATLAS, CMS, and ALICE to explore beyond-Standard-Model signatures. The upgrade integrates advances in detector technology from institutions such as University of Oxford, Imperial College London, INFN, CERN member states, and partners in Japan, United States, and Russia.

Overview

The upgrade transforms the experiment's front-end and readout to handle full 40 MHz Large Hadron Collider bunch-crossing rates, replacing legacy subsystems with modern pixel and microstrip trackers developed by teams at University of Manchester, University of Geneva, University of Zurich, INFN and contributors from France, Germany, and Spain. It coordinates with accelerator projects such as the High-Luminosity Large Hadron Collider and interacts with detectors like LHCb's predecessors and contemporaries including BaBar, Belle, and Tevatron experiments for complementary heavy-flavour results. Governance and funding involve agencies such as European Research Council, national funding councils, and intergovernmental agreements tied to CERN operations.

Motivation and goals

Motivation stems from open questions in flavour physics that implicate extensions beyond the Standard Model explored also by searches at ATLAS and CMS. Key goals include improved measurements of CKM matrix parameters tied to work by physicists following the Kobayashi–Maskawa theory and experimental milestones like those from Belle II and BaBar. The upgrade aims to increase integrated luminosity reach to probe rare processes observed at experiments such as CLEO and LHCb Run 1 and Run 2, reduce systematic uncertainties parallel to lattice QCD advances from groups linked to USQCD, and enable precision tests related to anomalies noted by collaborations including Muon g-2 and BESIII.

Detector upgrades

Major hardware changes include replacement of the vertex detector with a pixel-based system developed in partnership with Vertex 2020 initiatives and institutions like CERN microelectronics groups, new silicon microstrip tracker modules inspired by designs used at ATLAS's inner tracker upgrades, and upgraded ring-imaging Cherenkov detectors collaborating with teams from University of Cambridge and Nikhef. Calorimetry and muon systems are refurbished drawing on experience from CMS and DØ muon designs, while radiation-hard electronics leverage developments from RD53 projects and CERN microelectronics programmes. Sensor technologies include hybrid pixel detectors and silicon microstrip designs prototyped at facilities such as Paul Scherrer Institute and DESY, with cooling and mechanics contributions from groups at Rutherford Appleton Laboratory and STFC.

Trigger and data acquisition

The upgrade implements a fully software-based trigger architecture replacing a hardware Level-0 stage, following trends set by ATLAS and CMS upgrades and influenced by computing models from LHC Computing Grid and projects like Worldwide LHC Computing Grid. A flexible real-time analysis framework allows analyses akin to those pioneered in Alice and Belle II, with event-builder networks, FPGA-based front-end boards developed with industry partners, and high-performance farms using servers from vendors working with CERN procurement. Data reduction techniques integrate machine-learning algorithms similar to applications in ImageNet-related research and efforts in High Performance Computing centres, while time-alignment and calibration strategies borrow lessons from CLEO-c and BaBar experiments.

Commissioning and performance

Commissioning phases involved tests with beam from the Super Proton Synchrotron and cosmic-ray runs coordinated with CERN accelerator schedules, followed by staged integration validated against simulation frameworks used by collaborations such as GEANT4 and reconstruction toolkits shared with ATLAS and CMS. Early performance metrics showed improvements in vertex resolution comparable to upgrades at Belle II and momentum resolution approaching designs discussed by Particle Data Group benchmarks. Radiation tolerance tests reference standards from IEC and joint studies with institutes like CERN's Radiation to Electronics group and École Polytechnique Fédérale de Lausanne.

Physics reach and expected impact

With higher instantaneous luminosity and a 40 MHz readout, the experiment will enhance sensitivity to rare decays including channels studied by LHCb earlier and by CMS and ATLAS complementary searches, sharpen measurements of CKM angles paralleling analyses from Belle II and global fits coordinated by the CKMfitter Group and UTfit Collaboration, and probe lepton-flavour universality anomalies reported in datasets compared with results from BABAR and Belle. Expected impacts span constraints on models such as Supersymmetry, Z' models, and scenarios considered in theoretical work by researchers connected to CERN Theory Department and universities like Princeton University and University of California, Berkeley. Results will feed into precision tests referenced in reviews by the Particle Data Group and inform future facilities including the Future Circular Collider and proposals such as the International Linear Collider.

Category:Particle physics experiments