Neutrinos, tiny and neutrally charged particles, have long been a subject of fascination for physicists. While they are believed to be abundant in the universe, their elusiveness has posed a significant challenge to researchers. However, recent breakthroughs in the field have led to the observation of neutrinos inside colliders, opening up new possibilities for experimental particle physics research. In this article, we will explore the two groundbreaking studies conducted by the FASER (Forward Search Experiment) and SND (Scattering and Neutrino Detector)@LHC collaborations at CERN’s Large Hadron Collider (LHC) in Switzerland.
Neutrinos, as the least well-studied particles in the Standard Model of particle physics, have proven to be elusive due to their weak interaction with other particles. Detecting these particles requires advanced equipment and detectors positioned in strategic locations, such as near known sources of neutrinos. Previous efforts have successfully observed neutrinos originating from various cosmic objects, as well as particle accelerators and nuclear reactors. However, the observation of neutrinos inside colliders has remained a long-standing goal.
The FASER collaboration, established with the aim of observing light and weakly interacting particles, achieved a significant milestone by detecting neutrinos at the LHC. Their detector, positioned over 400m away from the ATLAS experiment in a separate tunnel, captured the first collider neutrinos. By placing the detector along the beam line, FASER was able to observe the trajectories of high-energy neutrinos predominantly produced in the LHC’s interaction region. The successful detection of 153 neutrinos with a small and inexpensive detector highlights the potential for high-energy experiments to contribute to the study of neutrinos.
Another major breakthrough came from the SND@LHC collaboration, which established a specific experiment to detect neutrinos. They strategically positioned their detector, two meters in length, at a site in the LHC where the flux of neutrinos is high. Shielded from proton collision debris by concrete and rock, the detector faced the challenge of distinguishing neutrino interactions from the background produced by high-energy muons. Nevertheless, the SND@LHC collaboration successfully recorded collider neutrino events, paving the way for further investigations.
The observation of collider neutrinos marks a significant turning point in the field of particle physics. For over 50 years, particle colliders have detected every known particle except for neutrinos. The detection of neutrinos from a new source, such as a collider, has historically provided crucial insights into the universe. By observing collider neutrinos, physicists can now explore their properties in greater detail and potentially uncover new particles that have eluded detection.
One of the remarkable aspects of the collider neutrinos detected by both the FASER and SND@LHC collaborations is their exceptionally high energy. These high-energy neutrinos present a unique opportunity to conduct in-depth studies and search for other elusive particles. The properties of neutrinos hold valuable clues to understanding the mysteries of the Standard Model of particle physics, including the existence of three generations of matter particles. Additionally, the strategic positioning of the SND@LHC detector in a blind spot for larger LHC experiments allows for a better understanding of the structure of colliding protons.
The recent breakthroughs by the FASER and SND@LHC collaborations have propelled experimental particle physics research forward. With the confirmation of neutrinos at the LHC, these collaborations will continue to collect data and explore further observations. The FASER collaboration plans to run their detector for many more years, significantly expanding the dataset. They also have plans to utilize the full power of the FASER detector to map out high-energy neutrino interactions in exquisite detail. Moreover, the Forward Physics Facility proposal aims to build a new underground cavern at the LHC, enabling the detection of millions of high-energy neutrinos and the search for phenomena associated with dark matter.
The observation of collider neutrinos at the LHC marks a significant milestone in particle physics. The breakthroughs achieved by the FASER and SND@LHC collaborations have opened up new avenues for exploring the properties of neutrinos and searching for other elusive particles. As experiments continue to collect data and new technologies are developed, the study of neutrinos inside colliders holds immense potential for advancing our understanding of the universe and the fundamental laws of physics.
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