Scientists Detect Neutrinos Produced in Particle Collider for the First Time
In a groundbreaking achievement, scientists have successfully detected neutrinos created in a particle collider for the first time. Neutrinos, also known as “ghost particles,” are enigmatic subatomic particles that have eluded direct observation due to their elusive nature. However, this recent discovery opens up new possibilities for understanding the formation, properties, and role of neutrinos in the evolution of the Universe.
The groundbreaking results were obtained using the FASERnu detector at the Large Hadron Collider (LHC). Researchers presented their findings at the 57th Rencontres de Moriond Electroweak Interactions and Unified Theories conference in Italy in March 2023, marking the first direct observation of collider neutrinos.
Particle physicist Jonathan Feng from the University of California Irvine explained the significance of the discovery, stating, “We’ve discovered neutrinos from a brand-new source – particle colliders – where you have two beams of particles smash together at extremely high energy.”
The detection of collider neutrinos has been eagerly anticipated in the scientific community, and the publication of two peer-reviewed papers solidifies the significance and excitement surrounding this achievement. Neutrinos are among the most abundant subatomic particles in the Universe, second only to photons. Despite their abundance, neutrinos possess no electric charge, have an almost negligible mass, and barely interact with other particles they encounter. In fact, hundreds of billions of neutrinos are constantly passing through our bodies at this very moment.
Neutrinos are typically produced under energetic circumstances such as nuclear fusion inside stars or supernova explosions. Although they interact very weakly with matter, they occasionally collide with other particles, producing faint bursts of light. Underground detectors, shielded from other sources of radiation, are capable of capturing these bursts. Notable detectors include IceCube in Antarctica, Super-Kamiokande in Japan, and MiniBooNE at Fermilab in Illinois.
However, detecting neutrinos produced in particle colliders has been a long-standing goal for physicists. The high energies involved in particle colliders offer unique opportunities for studying neutrinos that were previously unexplored. Particle physicist Jamie Boyd from CERN explained that high-energy neutrinos in the LHC could provide valuable insights into particle astrophysics and deep space.
The FASERnu detector used in this study consists of millimeter-thick tungsten plates alternating with layers of emulsion film. Tungsten was chosen for its high density, which increases the likelihood of neutrino interactions. The detector, consisting of 730 emulsion films with a total tungsten mass of around 1 ton, captures the particle tracks left by neutrinos colliding with nuclei in the tungsten plates.
The researchers initially identified six neutrino candidates in 2021, and their recent confirmation of the discovery using data from the upgraded LHC’s third run provides high confidence in the results. The significance level of 16 sigma implies an extremely low likelihood of the signals being produced by random chance. In particle physics, a significance level of 5 sigma is considered sufficient to qualify as a discovery.
The FASER team continues to analyze the data collected by the detector, and many more neutrino detections are expected as the LHC’s Run 3 extends until 2026. Physicist David Casper from UC Irvine projected that around 10,000 neutrino interactions would be observed during this run, indicating the vast potential of the FASERnu detector.
With the successful observation of neutrinos at the LHC, the collider’s full physics potential is finally being harnessed, according to Casper. This breakthrough opens up exciting avenues for further research into neutrinos and their role in shaping the Universe.
The team’s remarkable results have been published in the esteemed journal Physical Review Letters. This groundbreaking discovery in particle physics promises to deepen our understanding of neutrinos and provide critical insights into the fundamental nature of the Universe.
(A version of this article was first published in March 2023.)