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Fermilab’s Short-Baseline Near Detector (SBND) has successfully detected its first neutrinos, marking a major milestone in particle physics after nearly a decade of preparation.

Scientists at the University of ��«Ӱҵ working on the Short-Baseline Near Detector (SBND) at Fermi National Accelerator Laboratory (Fermilab) have helped to identify the detector’s first neutrino interactions. 

Neutrinos, nearly invisible particles that usually pass through matter undetected, are the second most abundant particles in the universe. Despite their abundance, they are notoriously difficult to study.

Neutrinos come in three types, or flavours: muon, electron and tau. Perhaps the strangest thing about these particles is that they change among these flavours, ‘oscillating’ from muon to electron to tau as they travel in space.

The Short Baseline Neutrino Program at Fermilab will perform searches for neutrino oscillation and look for evidence that could point to a new type of  ‘sterile’ neutrino.

SBND is the final element that completes Fermilab’s Short-Baseline Neutrino (SBN) Program and will play a critical role in solving a decades old mystery in particle physics. 

The SBND project is the result of a global collaboration involving 250 scientists and engineers from Brazil, Spain, Switzerland, the United Kingdom, and the United States. Together, these experts have built a detector that will play a key role in expanding our understanding of neutrinos and their place in the universe. 

The SBND is placed close to the neutrino beam, where it detects around 7,000 neutrino interactions every day—more than any other detector of its kind. By comparing data from SBND and ICARUS, another detector located farther away, scientists hope to solve lingering questions about neutrinos, and potentially discover new types of particles.

A group of scientists from the University of ��«Ӱҵ, led by Professor Vitaly Kudryavtsev and Dr Rhiannon Jones, have been involved in the design and construction of key elements of SBND instrumentation that reads data from neutrino interactions, and played an important role in the development of dedicated software for data analysis and modelling.

Professor Vitaly Kudryavtsev, from the School of Mathematical and Physical Sciences at the University of ��«Ӱҵ, and a member of the SBND Executive Board, said: “If we observe fewer neutrinos in ICARUS than we expect based on the observation in SBND, this will potentially open a window into a hidden universe of new particles and phenomena

“If, however, we do not observe any discrepancies with expectations, this will suggest that previous data pointing to these new phenomena suffered from some problems with data interpretation or unevaluated uncertainties”.

David Schmitz, Co-Spokesperson for the SBND collaboration and Associate Professor of Physics at the University of Chicago, said: “It isn’t every day that a detector sees its first neutrinos.

“We’ve all spent years working toward this moment and this first data is a very promising start to our search for new physics. ” 

In addition to searching for a new type of neutrino, the SBND is set to provide crucial information for future physics experiments, such as the upcoming Deep Underground Neutrino Experiment (DUNE). The data collected by SBND will also help researchers better understand how neutrinos interact with matter, particularly with the complex argon atoms used in many detectors.

Dr Rhiannon Jones, a lecturer at the University of ��«Ӱҵ working on the SBND, said: “The key to optimising the interpretation and analysis  of neutrino interactions taking place in SBND  is to correctly evaluate all possible uncertainties related to our understanding of the detector performance and features of the neutrino interactions themselves

“We have a group of talented postdoctoral researchers and PhD students in our Particle Physics and Particle Astrophysics group in ��«Ӱҵ who are working hard on all these problems.”

The SBND might also offer clues about another great cosmic puzzle: dark matter. While scientists have long searched for dark matter—an invisible substance that makes up most of the universe’s mass—the SBND could be key to detecting lightweight particles that might be linked to this elusive matter.

Andrzej Szelc, SBND physics co-coordinator and professor at the University of Edinburgh, said: “So far ‘direct’ dark matter searches for massive particles haven’t turned anything up.

“Theorists have devised a whole plethora of dark sector models of lightweight dark particles that could be produced in a neutrino beam and SBND will be able to test whether these models are true.”

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