Accelerator Report: Excellent Performance at the LHC

Why It Matters

Achieving nominal intensity and low‑pile‑up conditions accelerates the 2026 physics programme, enabling more precise measurements that could refine the Standard Model. The brief interruptions highlight aging infrastructure, underscoring the need for upgrades to maintain CERN’s research leadership.

Key Takeaways

• LHC achieved nominal Run 3 intensity of 1.8×10¹¹ protons per bunch
• Initiated three‑week low‑μ run to reduce pile‑up for precision W‑mass measurement
• Van der Meer scan scheduled for absolute luminosity calibration with prepared beams
• Cryogenic compressor failure caused three‑day LHC stop and injector power‑supply fault

Pulse Analysis

The Large Hadron Collider’s recent milestone—reaching its nominal Run 3 intensity—signals a pivotal moment for high‑energy physics. Operating at 1.8 × 10¹¹ protons per bunch, the accelerator now delivers luminosities that surpass original projections, providing the data volume needed for next‑generation discoveries. This performance boost not only validates years of upgrades across the injector chain but also positions CERN to meet the ambitious goals of its 2026 physics programme, where precision and statistical power are paramount.

A central feature of the current schedule is the three‑week low‑μ run, deliberately lowering the average number of simultaneous proton‑proton interactions per bunch crossing. By reducing pile‑up from the typical 64 collisions to a much cleaner environment, experiments such as ATLAS and CMS can sharpen measurements of the W boson mass and explore subtle electroweak effects with unprecedented accuracy. The low‑pile‑up dataset also opens doors for heavy‑flavour and diffractive studies, where background suppression is critical. Complementing this effort, a Van der Meer scan will calibrate the absolute luminosity scale, leveraging specially prepared beams that undergo precise shaping in the PS Booster, PS, and SPS before injection into the LHC.

Operational resilience remains a focus as unforeseen technical issues surfaced. A cryogenic compressor at Point 18 exhibited rapid bearing degradation, prompting an early three‑day shutdown, while a major fault in the PS power‑supply (POPS) required component replacement. These incidents underscore the aging of key infrastructure and reinforce the urgency of planned upgrades, such as the POPS+ replacement slated for LS3. Despite the setbacks, the accelerator complex’s overall health is strong, and the continued delivery of high‑intensity beams ensures that CERN stays at the forefront of particle‑physics research.