The CMS Week 2026 at CERN provided an opportunity for the collaboration to review the current status of the experiment, highlight recent scientific and technical achievements, and discuss preparations for the HL-LHC era. The opening plenary brought together reports from the Spokesperson, Run Coordination, Trigger, Computing, Physics, and Technical Coordination teams, offering a broad overview of CMS activities and outlining priorities for the coming years. Particular emphasis was placed on the lessons learned from Run 3 and on the challenges associated with operating and upgrading the experiment for future high-luminosity running.
A major focus throughout the week was the progress of the Phase-2 upgrade program. Dedicated meetings and plenary sessions covered the Tracker, ECAL, HCAL, HGCAL, Muon systems, MTD, PPS, Trigger, DAQ, and Computing infrastructures. These discussions highlighted achievements in detector construction, commissioning, integration, and operations, while also presenting plans for LS3 and the roadmap toward Run 4. Together, they demonstrated the scale of the effort required to prepare CMS for the significantly increased data rates and physics opportunities of the HL-LHC.
The physics program featured updates from a wide range of analysis groups, including Higgs, top quark, flavour, electroweak, heavy-flavour, exotic, and long-lived particle searches. Presentations showcased recent Run 3 results, ongoing analyses, and future prospects, illustrating the continued breadth and vitality of the CMS physics program. Several sessions also focused on low-pileup studies and preparations for future analyses in Run 4 and beyond.
The week also highlighted several contributions from our group. During the B Physics meeting on Tuesday, Zhangqier Wang presented a comparison of dimuon and ditrack reconstruction efficiencies throughout Run 3, an important input for a number of ongoing analyses. On Thursday, Jan Eysermans delivered a plenary talk on the status of the low-pileup physics program using the 2026 data set, which will play a key role in future precision measurements, including a new determination of the W boson mass. The plenary program also included a report on diboson polarization measurements in Run 3, highlighting our continuing contributions to vector boson scattering analyses towards the measurement of the longitudinal polarization component.
Another recurring theme was the increasing role of advanced computing and machine learning in CMS. Discussions covered developments in trigger systems, real-time reconstruction and calibration, analysis preservation, real-time datasets, and machine-learning-based algorithms. The poster session further highlighted innovative work across the collaboration, ranging from detector technologies and operations to reconstruction techniques and physics analyses, with strong participation from students and early-career researchers.
The week also included several events celebrating the collaboration and its community. CMS Awards recognized outstanding contributions across the experiment, including the recognition of Kirill Ivanov for his contributions to the PPD program. Special presentations also marked the milestone of more than 1500 CMS publications and reflected on the history of the experiment.
Overall, CMS Week 2026 highlighted a collaboration that is simultaneously delivering a rich Run 3 physics program and making substantial progress toward the detector, software, trigger, and computing capabilities required for Run 4 and the HL-LHC era. The discussions throughout the week reflected both the achievements of the present and the ambitious preparations underway for the future of CMS.