A multidisciplinary and international team of 250 scientists at the U.S. Department of Energy’s Fermi National Accelerator Laboratory (Fermilab) has identified the first neutrino interactions in its Short-Baseline Near Detector. This detection of neutrinos is the result of a decade of planning, prototyping and the building of the Short-Baseline Near Detector (SBND) itself. Researchers from the University of Granada, specifically the Department of Theoretical and Cosmic Physics, have been part of the team from the beginning.
Diego García Gámez, a member of the team from Granada, highlighted the UGR’s contribution, which included “coordinating and developing both the simulation and reconstruction algorithms for the scintillation light, as well as the system for detecting it in the experiment, in addition to leading studies on the search for hyperons, pion production in charged current processes and coherent production of mesons”.
García Gámez explains that, right now, the Standard Model is the best theory for how the universe works at its most fundamental level. It is the gold standard particle physicists use to calculate everything from high-intensity particle collisions in particle accelerators to very rare decays. “But despite being a well-tested theory, the Standard Model is incomplete,” he says. And over the past 30 years, multiple experiments have observed anomalies that may hint at the existence of a new type of neutrino, the second most abundant particle in the universe. Yet, despite being so abundant, they are incredibly difficult to study because they only interact through gravity and the weak nuclear force, meaning they almost never appear in a detector. To date, neutrinos have been classified into three types, or flavours: muon, electron and tau. What makes them even more difficult to study is the fact that these particles are capable of changing flavours, oscillating from muon to electron to tau.
Scientists have a fairly good idea of how many of each type of neutrino should be present at different distances from a neutrino source. However, the observations did not match those predictions, which could mean that there are more than the three known types of neutrinos. The Fermilab Short-Baseline Neutrino Programme, of which the UGR is a part, will study neutrino oscillations and will look for evidence that can definitively confirm or reject the existence of this fourth neutrino. SBND is the near detector for the programme, measuring neutrinos as they are produced in the beam. ICARUS, which began collecting data in 2021, acts as the far detector and will measure the neutrinos after they have potentially oscillated.
Beyond the hunt for new neutrinos
SBND has an exciting physics programme of its own. Because it is located so close to the neutrino beam, SBND will see 7,000 interactions per day, more neutrinos than any other detector of its kind. The large data sample will allow researchers to study neutrino interactions with unprecedented precision. “We will collect 10 times more data on how neutrinos interact with argon than all previous experiments combined,” says Ornella Palamara, Fermilab scientist and co-spokesperson for SBND. “So, the analyses that we do will be also very important for DUNE.”
Contact details: Diego García Gámez
Translated version: This text has been translated into English by the Language Services Unit (Vice-Rectorate for Internationalization) of the University of Granada.
