CERN's Large Hadron Collider Makes Its First Observations of Neutrinos

Physicists have observed neutrinos originating "from the sun, cosmic rays, supernovae and other cosmic objects, as well as particle accelerators and nuclear reactors," writes Phys.org. But one remaining goal was observing neutrinos inside "collider" particle accelerators (which direct two particle beams). It's now been accomplished using neutrino detectors located at CERN's Large Hadron Collider (LHC) in Switzerland by two distinct research collaborations: - FASER (Forward Search Experiment)- SND (Scattering and Neutrino Detector)@LHC Phys.org argues the two achievements "could open important new avenues for experimental particle physics research. "The results of their two studies were recently published in Physical Review Letters. "Neutrinos are produced very abundantly in proton colliders such as the LHC," Cristovao Vilela, part of the SND@LHC Collaboration, told Phys.org. "However, up to now, these neutrinos had never been directly observed. The very weak interaction of neutrinos with other particles makes their detection very challenging and because of this they are the least well studied particles in the Standard Model of particle physics...." "Particle colliders have existed for over 50 years, and have detected every known particle except for neutrinos," Jonathan Lee Feng, co-spokesperson of the FASER Collaboration, told Phys.org. "At the same time, every time neutrinos have been discovered from a new source, whether it is a nuclear reactor, the sun, the Earth, or supernovae, we have learned something extremely important about the universe. As part of our recent work, we set out to detect neutrinos produced at a particle collider for the first time... "Because these neutrinos have high fluxes and high energies, which makes them far more likely to interact, we were able to detect 153 of them with a very small, inexpensive detector that was built in a very short time," Feng explained. "Previously, particle physics was thought to be divided into two parts: high energy experiments, which were required to study heavy particles, like top quarks and Higgs bosons, and high intensity experiments, which were required to study neutrinos. This work has shown that high energy experiments can also study neutrinos, and so has brought together the high-energy and high-intensity frontiers." The neutrinos detected by Feng and the rest of the FASER collaboration have the highest energy ever recorded in a laboratory environment.... Cristovao Vilela, part of the SND@LHC Collaboration, said "The observation of collider neutrinos opens the door to novel measurements which will help us understand some of the more fundamental puzzles of the Standard Model of particle physics, such as why there are three generations of matter particles (fermions) that seem to be exact copies of each other in all aspects except for their mass. Furthermore, our detector is placed in a location which is a blind spot for the larger LHC experiments. Because of this, our measurements will also contribute to a better understanding of the structure of colliding protons."

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