Neutrinos, the tiny and neutrally charged particles accounted for by the Standard Model of particle physics, have long posed a significant challenge for physicists. Despite being some of the most abundant particles in the universe, their elusive nature makes them difficult to detect due to their low interaction probability with other matter. However, recent breakthroughs have allowed two research efforts, FASER and SND@LHC, to observe collider neutrinos for the first time. This article explores the significance of this discovery and the potential impact on experimental particle physics.
For years, physicists have utilized detectors and advanced equipment to study known sources of neutrinos. These efforts led to the observation of neutrinos originating from the sun, cosmic rays, supernovae, particle accelerators, and nuclear reactors. However, the ultimate goal was to detect neutrinos inside colliders, particle accelerators where two beams of particles collide. Recent research collaborations, FASER and SND@LHC, accomplished this feat by observing collider neutrinos using detectors located at CERN’s Large Hadron Collider (LHC) in Switzerland, as detailed in their studies published in Physical Review Letters.
The FASER collaboration, established with the aim of observing light and weakly interacting particles, was the first to detect neutrinos at the LHC. Their detector, positioned over 400m away from the ATLAS experiment in a separate tunnel, captured neutrinos produced in the same interaction region as ATLAS. By placing their detector along the beam line, the FASER collaboration successfully observed 153 high-energy neutrinos that were previously inaccessible to other detectors at the LHC. This breakthrough brings together the high-energy and high-intensity frontiers of particle physics, expanding the scope of scientific exploration.
The SND@LHC collaboration conducted a complementary study to the FASER experiment, finalizing their analysis shortly after FASER reported the first observation of collider neutrinos. Their experiment utilized a two-meter-long detector strategically positioned at a site in the LHC with a high flux of neutrinos, shielded from proton collision debris by concrete and rock. Overcoming the challenge of background noise from muons, the SND@LHC collaboration successfully identified 8 additional neutrino events in the LHC data. Their analysis of the data collected during their first operation cycle marks a significant step forward in understanding neutrino interactions.
The observation of collider neutrinos opens up exciting possibilities for understanding the mysteries of the Standard Model of particle physics. The SND@LHC collaboration believes that studying collider neutrinos will shed light on fundamental puzzles, such as why there are three generations of matter particles that appear almost identical except for their mass. Additionally, these experiments provide valuable insights into the structure of colliding protons, as the SND@LHC detector is strategically located in a blind spot of larger LHC experiments. The data collected by both collaborations will contribute to a more comprehensive understanding of particle physics.
The recent breakthroughs by the FASER and SND@LHC collaborations mark significant milestones in experimental particle physics research. With the presence of neutrinos at the LHC confirmed, these experiments will continue to collect data, potentially leading to more meaningful observations. The FASER collaboration plans to run their detector for many more years, collecting ten times more data and utilizing the full power of FASER to study high-energy neutrino interactions in detail. Moreover, the Forward Physics Facility, a proposed underground cavern at the LHC, holds the promise of detecting millions of high-energy neutrinos and exploring phenomena associated with dark matter.
The groundbreaking discovery of collider neutrinos by the FASER and SND@LHC collaborations opens up new avenues for experimental particle physics research. The observation of these elusive particles at the LHC not only contributes to our understanding of neutrinos but also offers insights into the fundamental nature of the universe. With ongoing data collection and future advancements, these experiments hold the potential for further breakthroughs and a deeper understanding of the mysteries of particle physics.