First-Ever Oxygen Collisions at CERN's Large Hadron Collider

In a groundbreaking event, CERN's Large Hadron Collider (LHC) has successfully conducted its first-ever collisions of oxygen ions, marking a significant milestone in high-energy particle physics. This operation commenced on June 29 and will continue until July 9, 2025, encompassing a series of complex experiments designed to deepen our understanding of fundamental physics. The LHC, located near Geneva, Switzerland, is the world's largest and most powerful particle accelerator, known for its contributions to the discovery of the Higgs boson and studies related to the early universe.

The current experimental campaign will include proton-oxygen collisions, followed by oxygen-oxygen and neon-neon collisions. According to Roderik Bruce, an LHC ion specialist, the challenge of proton-oxygen collisions arises from the differing charge-to-mass ratios of the particles. "The electromagnetic field inside the accelerator affects protons and oxygen ions differently, which complicates the precise positioning of collisions," he explained. Engineers at CERN have meticulously adjusted the frequencies and momenta of the beams to ensure that the collisions occur at the designated points within the LHC's four main experiments: ALICE, ATLAS, CMS, and LHCb.

This campaign has generated excitement among scientists, as it promises to yield valuable data on cosmic rays and the strong force, potentially enabling the study of quark-gluon plasma—a state of matter thought to exist just after the Big Bang. The LHCf experiment, which focuses on cosmic ray research, has also prepared for this campaign by installing a detector along the beamline to capture secondary particles produced during collisions.

CERN's preparations for this operation date back to mid-April 2025, with initial feasibility studies starting in 2019. Each machine within the accelerator complex required specific configurations to handle oxygen and neon ions, which are generated in the Linac3 facility before being injected into the Low-Energy Ion Ring (LEIR) and further along the acceleration chain.

As the oxygen beams collide, scientists anticipate encountering challenges such as 'beam pollution,' a phenomenon not typically seen with proton beams. This occurs when secondary particles, created during collisions, share similar properties with oxygen ions, complicating data analysis. Bruce noted that the degree of this transmutation effect is still under investigation, and adjustments may be necessary to maintain the purity of the beam.

This initiative reflects the ongoing commitment of CERN to push the boundaries of scientific knowledge and technology. The findings from these experiments could have profound implications for our understanding of the universe and the fundamental forces that govern it. As the LHC embarks on this new phase, researchers worldwide eagerly await the insights that will emerge from these unprecedented collisions.

This operation aligns with CERN's broader objectives of advancing particle physics and enhancing global scientific collaboration. As stated by Dr. Fabiola Gianotti, Director-General of CERN, "This campaign is not just a technical achievement; it is an opportunity to explore new frontiers in our understanding of the universe."

In conclusion, the current experimental campaign at the LHC marks a historic moment in particle physics, paving the way for future discoveries that could reshape our comprehension of the fundamental forces at work in the universe. As CERN continues to innovate and explore, scientists remain optimistic about the potential breakthroughs that await from these pioneering experiments.